This is the accepted version of the article: Aurell, Marcos; Bádenas, B.; Castanera, Diego; [et al.]. «Latest Jurassic-Early Cretaceous synrift evolution of the Torrelapaja Subbasin (Cameros Basin) : implications for Northeast Iberia palaeogeography». Cretaceous Research, Vol. 128 (December 2021), art. 104997. DOI 10.1016/j.cretres.2021.104997 This version is available at https://ddd.uab.cat/record/248977 under the terms of the license 1 Latest Jurassic–Early Cretaceous synrift evolution of the Torrelapaja Subbasin 2 (Cameros Basin): implications for Northeast Iberia palaeogeography 3 Aurell, M. (1); Bádenas, B. (1); Castanera, D. (2); Gasca, J.M. (1); Canudo, J.I. (1); Laita, E. (1); Liesa, C.L. 4 (3) 5 (1) Grupo Araragosaurus-IUCA, Departamento de Ciencias de la Tierra. Universidad de Zaragoza, 50009 Zaragoza, Spain 6 (2) Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona, c/Escola Industrial 23, 08201, 7 Sabadell, Barcelona, Spain 8 (3) Grupo Geotransfer, IUCA, Departamento de Ciencias de la Tierra. Universidad de Zaragoza, 50009 Zaragoza, Spain 9 10 11 ABSTRACT 12 The reconstruction of the latest Jurassic–Early Cretaceous evolution of the Torrelapaja Subbasin 13 (Cameros Basin, Spain) resulted in the characterization of three synrift sequences (SS-1, SS-2 and SS-3) 14 bounded by major unconformities. Three major NW-SE normal faults combined with smaller scale faults 15 of variable direction (around NE-SW) controlled the sedimentation. The complex geometry of the 16 Torrelapaja Subbasin indicates a main extension direction of NE-SW, and a secondary NW-SE extension. 17 Sedimentation of the Tithonian–middle Berriasian SS-1 occurred in alluvial fan systems, grading upwards 18 to carbonate palustrine-lacustrine environments. A new vertebrate site with large size sauropod bones 19 has been found in the middle part of SS-1. The lower boundary of the uppermost Hauterivian–lower 20 Barremian SS-2 is locally a palaeokarst, with sedimentary infill including three new fossil sites with 21 remains of ornithopod, sauropod and theropod dinosaurs. Sedimentation of SS-2 encompasses distal 22 alluvial terrigenous facies with local palaeosoils and palustrine-lacustrine limestones grading upwards to 23 middle-distal alluvial facies. After a late Barremian–early Albian stratigraphic gap, sedimentation 24 resumed in coastal flat environments represented by the mudstones with intercalated skeletal (oyster- 25 rich) sandy limestones with carbonaceous plant remains of the SS-3. A middle-late Albian age assignment 26 of SS-3 based on regional correlation is supported by strontium isotopic data. This unit marks the first 27 Early Cretaceous marine incursion in the area from the northern Atlantic realm. This is a notable change 28 of the previous palaeogeographical reconstructions which established that the first marine 29 encroachment occurred in the early Aptian and was sourced from Tethysian domains. 30 Key words: Lower Cretaceous, continental sedimentation, extensional tectonics, dinosaurs, 31 palaeogeography, Northeast Iberia 32 33 1. INTRODUCTION 34 Extensional tectonics in the Iberian Basin rift system (Northeast Spain) around the Jurassic-Cretaceous 35 transition involved a major palaeogeographic change, from the setting of wide shallow-marine Jurassic 36 carbonate platforms, to continental-coastal sedimentation confined to locally subsident basins, 37 subbasins and troughs. The recorded uppermost Jurassic–Lower Cretaceous synrift deposits consist of 38 successive units separated by unconformities, the number and age of which vary from one sedimentary 39 domain to another (e.g., Salas et al., 2001; Mas et al., 2004; Liesa et al., 2019; Aurell et al., 2019b). 40 The Torrelapaja Subbasin is a relatively small (8x14 km) uppermost Jurassic–Lower Cretaceous subsident 41 area located in the southeastern edge of the Cameros Basin (Mas et al., 2002), in an area found relatively 42 close to the Maestrazgo Basin (Fig. 1A). The critical location of this subbasin between the two main 43 sedimentary domains of the latest Jurassic–Early Cretaceous Iberian Basin rift system makes its analysis 44 relevant to decipher the sedimentary evolution linked to the active extensional tectonics and to 45 understand the palaeogeography of Northeast Iberia during the latest Jurassic–Early Cretaceous. Initial 46 palaeogeographical reconstructions of Northeast Iberia considered that there was no marine connection 47 between the northern Cameros and the southern Maestrazgo sedimentary domains during the Early 48 Cretaceous (e.g., Canérot, 1974; García, 1982). However, the presence of coastal marine deposits 49 recorded in the upper part of the synrift succession in the Torrelapaja Subbasin was tentatively related 50 to an early Aptian transgressive event sourced from the southern Tethysian realm (Alonso and Mas, 51 1988, 1993). Based on this assumption, subsequent early Aptian palaeogeographical reconstructions of 52 Northeast Iberia (e.g., Salas et al., 2001; Mas et al., 2004; Suarez-González et al., 2013) proposed a 53 marine connection between the Cameros and Maestrazgo sedimentary domains through a narrow NW- 54 SE trending seaway located in the central part of the Iberian rift system. However, the data and 55 interpretation reported in our work does not support this Aptian marine connection. 56 Another point of interest of the uppermost Jurassic–Lower Cretaceous synrift successions of the Iberian 57 Basin rift system is the abundant presence of dinosaur fossil sites. The Cameros Basin has an important 58 record of dinosaur ichnites, especially in the provinces of Soria and La Rioja (e.g., Hernández-Medrano et 59 al., 2005; Moratalla and Hernán, 2010; Pérez-Lorente, 2015). Dinosaur fossil bones are known but in less 60 abundance (e.g., Canudo et al., 2010, Fuentes-Vidarte et al., 2016; Isasmendi et al., 2020). Within the 61 osteological record of Cameros, the Barremian–Aptian in the western domain (Burgos province) stands 62 out by its richness and high number of dinosaur type localities (e.g., Torcida Fernández et al., 2017). 63 Towards the east, the dinosaur fossil record is scarcer. In particular, dinosaur fossil occurrences 64 described so far in the Torrelapaja Subbasin are local and fragmentary (Royo-Torres et al., 2012; Rey- 65 Martínez and Royo-Torres, 2014). However, the data reported here show that this subbasin offers great 66 possibilities of a new significant vertebrate fossil record. 67 The main aim of this work is to characterize the latest Jurassic–Early Cretaceous tectono-sedimentary 68 evolution of the Torrelapaja Subbasin. Previous work on the area provided relevant structural, 69 stratigraphic and micropaleontological data (Schudack, 1987; Alonso and Mas, 1988, 1990; Martín- 70 Closas, 1989; Guimerà et al., 2004; Sacristán-Horcajada et al., 2011, 2012), but there is a lack of a 71 comprehensive and systematic study of the recorded sedimentary synrift successions. Accordingly, the 72 objectives of this work are: (1) to reconstruct the structure of the area, with the identification of 73 different sets of normal faults that controlled the tectono-sedimentary evolution; (2) to provide an 74 updated stratigraphic and sedimentological framework of the uppermost Jurassic–Lower Cretaceous 75 synrift successions, in order to reconstruct the depositional setting and its sedimentary evolution; (3) to 76 precise the age and palaeoenvironment of the new dinosaur fossil sites found in the course of our field 77 work, and those previously reported; (4) to discuss on the impact of the obtained results to a better 78 understanding of the palaeogeographic evolution of Northeast Iberia. Data and interpretations provided 79 here can be relevant for future tectono-sedimentary and paleontological research both on the studied 80 subbasin and nearby basins of Northeast Iberia. 81 82 2. GEOLOGICAL SETTING 83 The Torrelapaja Subbasin is defined here to include the Bigornia and Bijuesca troughs identified in 84 previous works (Mas et al., 2002; Guimerà et al., 2004; Sacristán-Horcajada et al., 2011, 2012). This 85 subbasin is located in the southeastern edge of the Cameros Basin (Fig. 1A), a large extensional basin 86 bounded by the so-called North and South Cameros faults. The Cameros Basin records an up to 8 km- 87 thick uppermost Jurassic–Lower Cretaceous dominant continental successions in its depocentral areas 88 (e.g. Mas et al. 2004, 2019; Guimerà et al., 2004; Casas et al., 2009; Clemente, 2010). The Torrelapaja 89 Subbasin is located between the South Cameros Fault and the Carabantes Fault System (Fig. 1B). 90 The Mesozoic stratigraphy of the study area is summarized in Figure 2. The Variscan basement is 91 unconformably overlain (D1 in Fig. 2) by the Triassic units deposited coeval to the initial stages of the 92 Mesozoic rifting. A regional angular unconformity is also common between the synrift Triassic and 93 postrift Jurassic sequences (San Román and Aurell, 1992; D2 in Fig. 2). The Jurassic sequence consists of 94 marine limestones and marls with variable overall thickness in the areas located north and south to the 95 South Cameros Fault. A nearly 1,000 m-thick marine Jurassic succession is recorded northwards 96 (Navarro-Vázquez, 1991), whereas south of this fault, the Jurassic is substantially reduced (c. 400 m-thick 97 near Bijuesca village). Marine Jurassic sedimentation ended with the lower Kimmeridgian reefal, oolitic 98 and bioclastic limestones of the Torrecilla Fm (Alonso and Mas, 1990). During the rest of the 99 Kimmeridgian the marine areas were progressively shifted eastwards into the Tethysian domains of the 100 Maestrazgo Basin (e.g., Bádenas and Aurell, 2001; Aurell et al., 2019a), resulting in the mid- 101 Kimmeridgian regional prerift unconformity (D3 in Fig. 2). 102 The uppermost Jurassic–Lower Cretaceous synrift succession in the Torrelapaja Subbasin studied here 103 consists of up to 500 m-thick siliciclastic and carbonate deposits that have been assigned to the Bijuesca, 104 Ciria, Torrelapaja and Escucha formations (Fig. 2), following the lithostratigraphy used in previous 105 regional studies (Schudack, 1987; Martín-Closas, 1989; Guimerà et al., 2004). The age of the lower units 106 was constrained by ostracod and charophyte biostratigraphy by Martín-Closas (1989) and U. Schudack 107 and M. Schudack (2009), respectively. The Bijuesca and Ciria formations developed within the Tithonian– 108 middle Berriasian, whereas the Torrelaja Fm was assigned to the latest Hauterivian–early Barremian age. 109 An uppermost Albian regional unconformity separates the studied synrift sequences from the postrift 110 Upper Cretaceous successions (D4 in Fig. 2), which include the continental sandstones and mudstones of 111 the uppermost Albian–middle Cenomanian Utrillas Fm (up to 270 m in thickness), followed by the 450– 112 550 m-thick shallow marine Cenomanian–Campanian carbonate units (Alonso et al. 1993; García et al., 113 2004). 114 115 3. MATERIALS AND METHODS 116 The reconstruction of the sedimentary evolution of the Torrelapaja Subbasin reported here is based on 117 stratigraphical, sedimentological, structural and palaeontological data acquired following extensive field 118 work, geological mapping and logging, complemented with a review of the published information. The 119 workflow relevant to this research consisted of: (1) structural analysis and geological mapping with a 120 combination of fieldwork and analysis of high-resolution aerial imagery; (2) stratigraphical and 121 sedimentological analysis based on logging of the synrift uppermost Jurassic–Lower Cretaceous 122 successions in selected outcrops (see Fig. 3 for location), suplemented by petrographical analysis of rock 123 hard samples (limestones, sandstones) in thin sections and by mineralogical composition of muddy 124 lithologies; (3) palaeontological fieldwork including the recovery of macrovertebrate remains by surface 125 collection, the microfossil sampling of muddy lithologies in selected fossil-bearing horizons, and location 126 within the geological framework of the new and previously described dinosaur fossil sites; and (4) review 127 and integration of data sets, that resulted in the delineation of updated regional maps showing the 128 palaeogeography of the Northeast Iberia at significant time intervals. 129 The dinosaur bearing-horizons have been sampled for the analysis of their micropaleontological content 130 (screen-washed samples of 2–5 kg). Moreover, three well-preserved oyster shells found in the upper part 131 of the synrift succession in the Bigornia trough were sampled for strontium-isotopic analysis. The 87 132 Sr/86Sr isotopes were determined with a TIMS-Phoenix thermal ionization mass spectrometer at the 133 CAI Geocronología y Geoquímica Isotópica of the Universidad Complutense de Madrid (Spain). Isotopic 134 data were corrected for possible 87Rb interferences and were normalised to a value of 0.1194 for 87 135 Sr/86Sr in order to correct possible mass-fractionation. During the period of analysis, the NBS-987 136 standard gave an average 87Sr/86Sr value of 0.710245 ± 0.000019, which was used to correct the 137 measured values from a possible deviation referred to the standard. The analytical error of the 87Sr/86Sr 138 ratio referred to 2σ was 0.01%. 139 4. STRATIGRAPHIC REMARKS AND STRUCTURE OF THE TORRELAPAJA SUBBASIN 140 The geological mapping of the area including the Torrelapaja Subbasin (Figs. 3 and 4) shows the 141 distribution of lithostratigraphic units and main structural elements. The subbasin is bounded to the 142 northeast by the southwest-dipping Malanquilla Fault and, to the southwest, by the northeast-dipping 143 Carabantes Fault System (Carabantes Fault; Guimerà et al., 2004). The northeast-dipping Berdejo Fault 144 (or Cardejón Fault in Guimerà et al., 2004) separates the northern and southern Bigornia and Bijuesca 145 troughs. The uppermost Jurassic (Tithonian)–Lower Cretaceous sedimentary succession of the 146 Torrelapaja Subbasin characterized in this work is arranged in three synrift sequences bounded by major 147 unconformities that can be traced across the study area (Fig. 2): (1) synrift sequence-1 (SS-1) includes the 148 alluvial deposits of the Bijuesca Fm and the lacustrine to palustrine limestones of the Ciria Fm; (2) synrift 149 sequence-2 (SS-2) is formed by the mixed siliciclastic and carbonate continental succession of the 150 Torrelapaja Fm; (3) synrift sequence-3 (SS-3) is characterized by a transitional continental to marine 151 succession, with oyster-rich sandy-limestones with abundant plant debris, followed by coal-bearing 152 sandstones and shales typical of the Escucha Fm. Selected key field views of the synrift units and 153 bounding surfaces in the Bijuesca (Fig. 5) and in the Bigornia troughs (Figs. 6 and 7) are provided. 154 The lower boundary of SS-1 is the subaerial exposure surface developed on top of the prerift Jurassic 155 marine limestones. This discontinuity has an associated stratigraphic gap encompassing at least the late 156 Kimmeridigian. The individualization of the Torrelapaja Subbasin as a depositional area began with the 157 sedimentation of SS-1. The sequence includes two vertically and laterally related continental units: the 158 alluvial conglomerates, sandstones and mudstones of the Bijuesca Fm, and the palustrine-lacustrine 159 limestones of the Ciria Fm (Fig. 5A). Most of the normal faults that were active during sedimentation of 160 SS-1 are NW-SE trending. Moreover, the northwestern Bigornia trough is compartmentalized by an 161 additional set of normal faults with perpendicular orientation (NE-SW). In the uplifted blocks, SS-1 is very 162 reduced and fossilizes normal faults affecting the marine Jurassic units (Fig. 4A-B; see also Alonso and 163 Mas, 1988, 1990; Sacristán-Horcajada et al., 2012). In the most subsident areas of the northwestern 164 Bigornia and Bijuesca troughs (Fig. 4A-C), the unit form thick successions (up to 350–400 m; see also 165 Alonso and Mas, 1990 and Sacristán-Horcajada et al., 2011, 2012), and the erosive gap of the underlying 166 marine Jurassic rocks is reduced. There, the lower boundary of SS-1 is generally a low-relief 167 paraconformity developed on top of the lower Kimmeridgian Torrecilla Fm (Fig. 5C). In the less subsident 168 areas of the southeastern Bigornia trough, the basal conglomerates of the Bijuesca Fm are 0–30 m-thick 169 and the sequence is dominated by the limestones of the 20–80 m thick Ciria Fm. 170 The lower boundary of SS-2 (Torrelapaja Fm) is the major unconformity between the lacustrine 171 limestones of the Ciria Fm (lower-middle Berriasian) and the continental terrigenous of the Torrelapaja 172 Fm (uppermost Hauterivian-lower Barremian). An irregular incised (some dm´s in deep) karstic surface is 173 frequently observed on top of the lacustrine limestones of SS-1 (Figs. 6A and 7A). The karstic cavities are 174 filled by argillaceous mudstones, which may include a rich assemblage of disarticulated vertebrate 175 remains (see section 6). Angular unconformities are commonly observed in the southeastern Bigornia 176 trough, where some of the NE-SW faults that were active during the sedimentation of SS-1 are fossilized 177 by SS-2 (Fig. 8). The Torrelapaja Fm (SS-2) includes a high variety of continental facies, mainly muddy 178 facies (from shales to calcareous mudstones) and intercalated limestones, conglomerates and 179 sandstones (Figs. 6C–F and 7D). The unit reaches maximum thickness of 60–80 m in the southeastern 180 Bigornia trough (Fig. 4B). By contrast, the unit is absent or very reduced in the southern Bijuesca trough 181 and in the northwestern edge of the Bigornia trough, where the postrift sandstones of the Utrillas Fm 182 usually overlay the SS-1 (Fig. 5A). 183 The lower boundary of SS-3 is a regional angular unconformity, which locally fossilizes normal faults that 184 were active during sedimentation of previous sequences (Fig. 3). SS-3 may directly overlay SS-1, as 185 observed in the northwestern part of the Bigornia through, in the outcrops located south of Ciria (Fig. 186 4A; see Alonso and Mas, 1988; Guimerà et al, 2004). The Escucha Fm (SS-3) is only found in the Bigornia 187 trough. Maximum thickness of the unit measured northeast of Berdejo village is around 50 m. There, the 188 unit consists of shales and burrowed micaceous sandstones rich in plant remains, with intercalation of 189 sandy skeletal limestones and abundant oyster debris (Fig. 7E-F). Its upper part is poorly exposed or 190 eroded across the Torrelapaja Subbasin and consists of sandstones and shales with interbedded coal 191 (lignite) levels. Lignite levels of the Escucha Fm were quarried south of Ciria village, in Vallehermoso (Fig. 192 4A). A borehole in this locality revealed the presence of a 33 m-thick succession of shales and siltstones 193 including intercalation of dm- to m-thick lignite beds (IGME, 1984). In its type locality, the Escucha Fm 194 has a similar lithological evolution, with a lower member dominated by sandy skeletal (oyster rich) levels 195 and a middle-upper part with abundant lignite levels (e.g., Querol et al., 1992). The upper boundary of 196 SS-3 is the major angular unconformity, which involved block tilting and erosion previous to the 197 deposition of the postrift deposits. The postrift Utrillas Fm rests on a low-angle unconformity and 198 fossilizes normal faults that were active during the sedimentation of the previous synrift sequences, as 199 observed east of Torrelapaja (Fig. 4B) or south of Bijuesca (Fig. 4C). 200 201 5. FACIES ANALYSIS: PALEOENVIRONMENTAL RECONSTRUCTION 202 5.1. Synrift sequence 1: Alluvial to palustrine-lacustrine systems 203 The SS-1 sedimentary system has been characterized in the most complete Bijuesca log (Sacristán- 204 Horcajada et al., 2011), complemented with new data of Las Cañadas log, located in the southeastern 205 Bigornia trough (see LC1 and BJ logs respectively in Figs. 4B and C). Further information of the 206 sedimentary evolution of SS-1 in the northwestern Bigornia trough is provided in Sacristán-Horcajada et 207 al. (2012). 208 The terrigenous clastic succession of the Bijuesca Fm represents deposition from proximal to distal 209 alluvial fans (Fig. 9A). In Bijuesca, the lower part of the succession is dominated by fining-upward 210 sequences of matrix-supported conglomerates with sandstone and limestone clasts. Inverse grading is 211 also observed. These deposits were interpreted as debris flow deposits of proximal alluvial fans 212 (Sacristan-Horcajada et al., 2011). The middle part of the Bijuesca Fm consist of clast-supported 213 conglomerates with cm-sized limestone pebbles and normal grading, fining-upward to cross-bedded 214 sandstones and red mudstones (Fig. 5F, G) deposited in channels and flood plains of middle alluvial fan 215 areas. Red mudstones with local root traces and intercalated cross-bedded sandstones dominate in the 216 upper part of the unit and represent deposition in a distal alluvial fan. Mudstones and nodular 217 (bioturbated) limestones with characean algae and gastropods at the topmost part of the unit indicates 218 the setting of carbonate palustrine subenvironments. The new dinosaur fossil site of La Atalaya occurs in 219 a palustrine level found at this topmost part, in the transition to the overlaying Ciria Fm (Fig. 5A-B; see 220 section 6). 221 During SS-1 there was an expansion of the lacustrine system of the Ciria Fm over the alluvial fans of the 222 Bijuesca Fm. The Ciria Fm was interpreted as a low-gradient ramp margin lake, mostly sourced from 223 spring waters (Sacristan-Horcajada et al., 2011). Carbonate saturated waters could be related to 224 discharges from karstic aquifers sourced from the Jurassic marine limestones. The Ciria Fm is 225 characterized by meter-thick sequences from lacustrine to palustrine facies (Fig. 9A-B). Lacustrine facies 226 encompass tabular meter-thick bioclastic limestones with characean algae, ostracods, gastropods and 227 bivalves. Limestones with bioclastic lime mudstones and wackestones represent deposition in low- 228 energy lacustrine areas. Bioclastic wackestones to packstones with intraclasts, quartz grains and black 229 pebbles formed in littoral to shallow lacustrine areas. The palustrine facies corresponds to 230 nodular/brecciated limestones bearing similar skeletal components than the lacustrine limestones, but 231 including evidences of edaphic processes (e.g., nodulization, brecciation, root traces, black pebbles, 232 fenestral porosity; Fig. 9C). The palustrine-lacustrine facies also include gray mudstones and marls and 233 local oncolitic limestones with cm-thick oncoids with bioclastic cores in Las Cañadas log (Fig. 9B-D). 234 In Las Cañadas the Ciria Fm includes sandstones and clast-supported conglomerates with sharp flat or 235 channelized bases and limestone pebbles. Their intercalation within the palustrine-lacustrine facies 236 reflects deposition in the distal alluvial fan area, with sheet flood deposits or channelized flows entering 237 in the lake. 238 5.2. Synrift sequence 2: Distal alluvial fans and shallow lakes 239 Facies analysis of sequence SS-2 (Torrelapaja Fm) is mainly based on the data collected in three logs 240 located in the eastern subsident areas of the Bigornia trough (see LC, VT and VJ logs in Fig. 4B). Three 241 terrigenous muddy facies have been differentiated based on colour and mineralogy (Fig. 10). Ochre to 242 purple mudstones and ochre to violet marlstones/calcareous mudstones include levels rich in Fe-pisoids 243 and root traces/hydromorphic soils and local reworked skeletal debris (ostracods, charophytes and 244 vertebrate remains). They represent deposition in distal alluvial plains with local vegetated areas and 245 lateritic soils. These facies are similar to those found in lateritic palaeosoils in age-equivalent units 246 characterized in the southern Maestrazgo Basin, as in the lower Blesa Fm (Oliete Subbasin: Laita et al., 247 2020). In contrast, gray marlstones/calcareous mudstones have more abundant ostracods, charophytes 248 and plant debris and some reworked Fe-pisoids, and preferentially accumulated in palustrine to shallow 249 lacustrine areas. 250 Limestones include a high variety of palustrine to shallow lacustrine facies (Fig. 11A). Bioclastic and 251 fenestral bioclastic limestones (wackestones/packstones, occasional grainstones) with abundant 252 bivalves, gastropods, ostracods and characean algae and some quartz grains (silt to medium sand), 253 dominate. The bioclastic limestones encompass subfacies with accumulated broken bivalves and 254 gastropods (Fig. 11B) or ostracods (Fig. 11C), both produced by hydrodynamic sorting by high-energy 255 events in lacustrine subenvironments. Other group of subfacies is dominated by ostracod and 256 charophytes deposited in quiet lacustrine areas (Fig. 11D). The fenestral bioclastic limestones with 257 abundant microcracks and root traces formed in palustrine areas (Fig. 11E). Two additional grain- 258 supported facies, tufa limestones and intraclastic/litoclastic sandy limestones are also present (Fig. 11A). 259 Tufa limestones include oncolitic subfacies with entire and broken oncoids (up to few cm-size) and 260 intraclasts (bioclastic facies, phytoclasts) in the matrix (Fig. 11F), as well as phytoclastic subfacies with 261 mm- to cm-size clasts of coated plant stems and stromatolites, oncoids and oncoid fragments (Figs. 6F 262 and 11G). The tufa limestones formed in palustrine-lacustrine areas as indicated by their intercalation 263 within gray marlstones/calcareous mudstones (Fig. 11A). The intraclastic/litoclastic facies is a mixture of 264 poorly sorted and variably rounded grains, including mm- to few cm-size lithoclasts (quartzite and 265 Jurassic limestones), intraclasts (e.g., muddy and bioclastic facies), oncoid fragments and quartz sand 266 grains (Fig. 11A). Nature of grains and lenticular geometries with channelized bases indicate deposition 267 by high-energy floods carrying lithoclasts from emerged areas and eroding both distal plain and 268 palustrine-lacustrine deposits. 269 Conglomerates and sandstones appear both as isolated tabular or lenticular beds and bed packages (dm 270 to few m-thick). The conglomerates are clast-supported with subangular to subrounded clasts up to 10 271 cm in size and granule to sand matrix. They have usual channelized bases, planar- and trough cross 272 bedding, cross- and parallel lamination, and normal gradation (Fig. 6E). Conglomerates with quartzite 273 (Paleozoic) and limestone (Jurassic) clasts dominate in the eastern section (Valdelavieja), intercalated 274 within distal alluvial plain facies (Fig. 11A). In contrast, conglomerates including only quartzite clasts are 275 recorded in Valdelatorre log. Fine to medium quartz sandstones have usual planar- and trough cross 276 bedding, cross- and parallel lamination, local ripples (Fig. 6C) and bioturbation (vertical traces). 277 Sandstones occasionally include coarse grains (quartzite and limestone clasts, intraclasts of lacustrine- 278 palustrine facies, Fe-pisoids, oncoid fragments) and bioclasts (bivalves, charophytes, ostracods). The 279 vertical relationships of sandstones and conglomerates with terrigenous muddy facies indicates that they 280 represent channels in middle-distal alluvial plain, reaching also subaqueous palustrine-lacustrine areas. 281 In turn, the isolated packages of conglomerates with quartzite clasts (Fig. 11A) indicate a different source 282 and are interpreted as channels of ephemeral braided streams within the plain. 283 The described facies have a lateral and vertically preferential distribution, which allow differentiating 284 three sedimentary stages (Figs. 10A and 12). Argillaceous Stage 1 corresponds to the sedimentary infill 285 on the paleokartic surface developed in the boundary between SS-1 and SS-2. It is dominated by muddy 286 facies of argillaceous composition (Fig. 11B) deposited in a distal alluvial plain with vegetated areas and 287 local lateritic soils. Lacustrine-palustrine areas comprise several vertebrate fossil sites (see section 6). 288 Carbonate-dominated Stage 2 reflects a rise in water level that led to the expansion of lacustrine- 289 palustrine areas and the increase in carbonate content in the distal plain (marlstone/calcareous 290 mudstones: see Fig. 10B), but also a coeval record of alluvial clastic input (sandstones) roughly from the 291 north and south (Figs. 11 and 13). In Stage 3, increase of terrigenous-clastic input resulted in the setting 292 of an asymmetrical sedimentary system. Southwards, middle-distal alluvial fan channels (conglomerates 293 with quartzite and limestone clasts, sandstones and muddy facies of predominant siliceous composition: 294 Fig. 10B) developed, and there was a significant reduction of lacustrine-palustrine areas to ponds. The 295 northern area was dominated by an alluvial-fluvial plain with terrigenous mudstone facies and with 296 ephemeral braided streams (conglomerates with quartzite pebbles). 297 5.3. Synrift sequence 3: coastal sedimentation 298 The Escucha Fm has been logged and sampled in an outcrop located south of Valdelavieja, where a 299 relatively thick succession (50 m) has been preserved from the post-rift erosion (Fig. 13A). There, the 300 Escucha Fm is dominated by yellowish to brown mudstones with dm- to m-thick intercalations of sandy 301 bioclastic limestones and sandstones. The terrigenous mudstones are mostly covered, but local small 302 outcrops allow to identify bivalves (including Trigonia bivalves and oyster shells of Exogyras) and thin 303 (few cm) levels rich in plant debris. The interbedded sandy bioclastic limestones (packstones) have 304 variable proportions of oyster fragments, whole and fragmented gastropods and serpulids, and quartz 305 grains (fine to medium sand). There are also echinoids spines, ostracods, brachiopods, carbonaceous 306 debris and both muddy and sandy intraclasts (Figs. 7F and 13B). The bivalve (oyster) sandy (quartz sand 307 grains) limestones are packstones characterized by accumulated debris of oysters, together with few 308 serpulids, gastropods and carbonaceous debris (Fig. 13C). These two facies have common bioturbation 309 with sedimentary infill consisting of silty lime mudstone texture. The top of the beds can be encrusted 310 and ferruginous, with frequent pholadid borings. Fine-grained sandstone beds with cross bedding and 311 cross- and parallel lamination are locally intercalated within the limestones. They contain lithic peloids in 312 the matrix and few bivalve debris. 313 Deposition of plant-rich terrigenous mudstones took place in low-energy terrestrial-coastal areas with 314 certain vegetal cover. Episodic marine flooding is indicated by the presence of levels with marine 315 bivalves. The sandy bioclastic limestones and sandstones represent deposition in a marine (probably 316 restricted embayed) area colonized mainly by oysters, gastropods and serpulids, and/or due to high- 317 energy events (storms) carrying quartz sand and skeletal debris from the open marine area. 318 Hydrodynamic sorting probably controlled the deposition of carbonate-rich and sandy beds, from well- 319 sorted accumulations of oysters in the bivalve sandy limestones, to poorly sorted sandy bioclastic 320 limestones with muddy and sandy intraclasts, to finer-grained sandstones. Bioturbation recorded in 321 limestones took place after the high-energy events. 322 323 6. DINOSAUR FOSSIL SITES: DESCRIPTION AND STRATIGRAPHIC SETTING 324 During the course of this investigation four new fossil dinosaur sites have been found. The La Atalaya 325 site, located 500 m southwest of Bijuesca village (see LA in Fig. 3), is up to now the only occurrence from 326 SS-1. The other three sites including dinosaur remains have been found in the lowermost levels of SS-2, 327 in the distal alluvial muddy facies (stage 1) that fills the irregular karstic surface developed on top of Ciria 328 Fm (Figs. 10A and 12A). The Corrales de Valdelavieja site is located about 2 km to the northeast of 329 Berdejo (see CV in Figs. 4B and 10A). The Corrales de Las Cañadas site is found 1.5 km northeast of 330 Torrelapaja village (see CC1 in Fig. 4B). The Valdelatorre site is located 1.7 km east from Torrelapaja 331 village (see VT in Fig. 4B and 10A). In this section we provide a brief description of their fossil content. 332 Besides, the data reported here have allowed to precise the stratigraphic setting of some previously- 333 known sites from the Bigornia trough (Royo-Torres et al., 2012; Rey-Martínez and Royo-Torres, 2014). 334 The La Atalaya fossil site yields a large-sized limb bone fragment and other large-sized caudal vertebra 335 assigned to Sauropoda indet. (Fig. 5D-E). Other vertebrate remains recovered by surface collection are 336 an archosaur rib fragment and some crocodylomorph osteoderms. The marly levels found in this 337 fossiliferous interval also hosts a microfossil assemblage including charophytes (poracharaceans), 338 ostracods (cyprideans), gastropods (planorbids and other two taxa), archosaur teeth (mainly 339 crocodylomorphs) and eggshells. This site is included in a bed of palustrine nodular limestone facies 340 found at the uppermost part of the Bijuesca Fm (Figs. 5A-B and 9A). Edaphic process linked to root 341 bioturbation produce nodulization and brecciation of these palustrine facies. However, the nodular 342 limestone of the fossiliferous site is in detail a laterally discontinuous carbonate conglomerate with 343 rounded clasts (Fig. 5D) produced by remobilization, transport and accumulation of the nodules and 344 breccia generated by the edaphic processes. This conglomerate bed laterally passes to marls with root 345 traces. Its location in the topmost part of the Bijuesca Fm points towards its age is around the Tithonian- 346 Berriasian transition. The Bijuesca Fm is assumed to be mostly Tithonian in age, although the precise 347 location of the Tithonian-Berriasian boundary within this unit is uncertain (Martín-Closas, 1989). The 348 early-middle Berriasian age of the overlaying Ciria Fm is locally constrained by charophyte 349 biostratigraphy (Martín-Closas, 1989), particularly by the association of Atopochara trivolvis var. horrida 350 and Nodosoclavator bradleyi found in the upper part of this unit (see Fig. 4A for location of the sampled 351 point). 352 The Corrales de Valdelavieja fossil site (lowermost Torrelapaja Fm) includes two theropod vertebrae (Fig. 353 6B) plus other indeterminate remains found in close contact to the karstic surface within the first stage 354 of muddy infill of the palaeokarst (ochre to red marlstones/calcareous mudstones; Fig. 10A). An 355 ornithopod (iguanodontian) tooth was also recovered from the overlaying intraclastic/litoclastic sandy 356 limestone. In addition, an isolated spinosaurid theropod tooth crown, which is slightly lateromedially 357 compressed and ornamented with longitudinal ridges was found ex-situ in a boulder of 358 intraclastic/litoclastic facies that forms part of the infill of the paleokarst. Terrigenous muddy facies filling 359 the palaeokarst (see sample CV1 in log VJ2, Fig. 10A) also includes a microfossil assemblage with latest 360 Hauterivian–early Barremian charophyte remains (Atopochara trivolvis ancora, A.t. triquetra, Globator 361 maillardii var. trochiliscoides), ostracods (cyprideans and other unidentified groups), eggshell fragments, 362 lissamphibian bone fragments and gastropods. Above this interval, samples CV2 and CV3 and has yielded 363 an early Barremian charophyte association with Atopochara triviolvis var. triquetra (typical form), 364 Clavator harrisii var. harrisii, Clavatoraxis sp and Charaxis (see VJ2 log in Fig. 10A and Fig. 6A for sample 365 location). 366 In the Corrales de Las Cañadas fossil site (lowermost Torrelapaja Fm), a set of isolated macrovertebrate 367 remains was found within the first stage of infill of the paleokarstic surface (ochre to red mudstones: Fig. 368 10A). The most significant fossil material comprises a sauropod humerus (Fig. 7B), a fragmentary 369 theropod ilium, and a saurischian vertebral centrum. Other indeterminate remains were found ex situ, 370 possibly eroded from the karstic infill. A poor microfossil assemblage of latest Hauterivian–early 371 Barremian age has been identified in this level (see sample LC1 in log LC, Fig. 10A). It includes remains of 372 ostracods (mainly cyprideans) and scarce charophytes (utriculi of Atopochara trivolvis ancora and A.t. 373 triquetra), some of them showing reworking features. 374 In the Valdelatorre fossil site (lowermost Torrelapaja Fm) an ornithopod vertebra was found ex-situ, very 375 close to the palaeokarstic surface developed on top of the Ciria Fm. Therefore, it is not possible to 376 ascertain whether it comes from the palaeokarst infill or was eroded from the overlaying muddy/marly 377 levels. The sediment sampling in a gray marlstone/calcareous mudstone bed on top of the vertebrate- 378 bearing bed (see VT1 microfossil sample in log VT, Fig. 10A) allowed to characterize an early Barremian 379 charophyte assemblage dominated by abundant utriculi of Atopochara trivolvis triquetra (typical form) 380 along with thalli of Clavatoraxis sp. Also frequent are ostracods (several taxa, including cyprideans), 381 eggshell fragments and microvertebrate remains dominated by undetermined lissamphibian bone 382 fragments along with crocodylomorph teeth (bernissartiids and goniopholidids). Moreover, osteichthyan 383 remains are present in less abundance (teeth of Lepisosteiformes and Amiiformes, and ganoid scales). 384 The composition of this microfossil assemblage resembles to those of other lower Barremian successions 385 reported in alluvial to shallow lacustrine settings from the Iberian Basin (e.g., Gasca et al., 2017). 386 In the area of Corrales de Valdelavieja and Valdelatorre, additional vertebrate sites were previously 387 reported by Royo-Torres et al. (2012) and Rey-Martínez and Royo-Torres (2014). These authors found 388 ornithopods and isolated remains of theropod and sauropod dinosaurs from five different sites named 389 BJ-1 to BJ-5 (see Figs. 4B and 10A for location of the most significant BJ1 and BJ5 sites). In particular, 390 Royo-Torres et al. (2012) described cranial and postcranial material of an ornithopod specimen in BJ-1 391 site, and their phylogenetic analysis consider it as a basal styracosternan. This site is found in meter 27 of 392 the VT log, towards the lower part of the Torrelapaja Fm (see Figs. 6D and 10A). Rey-Martínez and Royo- 393 Torres (2014) describe a distal end of a sauropod tibia in BJ-5 site, which is located 1 m above the base of 394 the Torrelapaja Fm (see VJ2 log in Fig. 10A). The authors assumed that all the BJ sites were included in 395 the Ciria Fm, and were “Tithonian and with some doubt Berriasian” in age. However, the review of these 396 fossil sites show that they are actually included in the lower part of the Torrelapaja Fm, and are 397 therefore early Barremian in age. 398 399 7. AGE OF SYNRIFT SEQUENCES AND REGIONAL CORRELATION 400 Below we review the age of the three identified synrift sequences based in previous information and 401 new data obtained in this work. According to the age assignment provided, the possible equivalence of 402 the sequences defined in the Torrelapaja Subbasin to the units defined in the depocentral areas of the 403 Cameros Basin and in the western domains of the nearby Maestrazgo Basin is proposed and discussed 404 (Fig. 14). 405 7.1. Synrift sequence 1: Tithonian-middle Berriasian 406 As indicated above, relevant data to precise the age of SS-1 is the presence of an early-middle Berriasian 407 charophyte association found in the upper part of the Ciria Fm with Atopochara trivolvis var. horrida and 408 Nodosoclavator bradleyi (Martín-Closas, 1989). Moreover, U. Schudack and M. Schudack (2009) 409 identified a rich Berriasian ostracod association, with different species of Cypridea, Theriosynoecum, 410 Mantelliana and Darwinula that points to freshwater environments for the sedimentation of the Ciria 411 Fm. Accordingly, at least the upper part of the of SS-1 (Ciria Fm) was coeval to the sedimentation of the 412 lower-middle Berriasian depositional sequence (Oncala Gr) defined in the Cameros Basin (DS-III in 413 Clemente, 2010; DS-3 in Quijada et al., 2013 and Mas et al., 2019). 414 The facies evolution recorded in the Torrelapaja Subbasin during the sedimentation of SS-1 (from alluvial 415 fan clastics to lacustrine limestones) shows that this unit corresponds to a single depositional sequence. 416 If a sequence-to-sequence correlation is done, SS-1 would be equivalent to the DS-III (Oncala Gr) of the 417 Cameros Basin. However, the particular tectono-sedimentary evolution of the Torrelapaja Subbasin 418 compared to the depocentral areas of the Cameros Basin leaves open the possible equivalence of the 419 lower part of the SS-1 to older Tithonian depositional sequences defined in the Cameros Basin (i.e. Tera 420 Group; DS I–II in Clemente, 2010 or DS 1–2 in Mas et al., 2019). In Figure 14 we suggest the possible 421 equivalence of the lower part of SS-1 with the DS-II (upper Tera Group), as previously proposed in 422 Sacristán-Horcajada et al. (2012). 423 7.2. Synrift sequence 2: uppermost Hauterivian-lower Barremian 424 The data reported here give further support to the latest Hauterivian–early Barremian age proposed for 425 the Torrelapaja Fm in previous works. Martín-Closas (1989) found a latest Hauterivian-earliest Barremian 426 association with Atopochara trivolvis triquetra (primitive form), Globator maillardii var. trochiliscoides 427 and Clavator calcitrapus in an isolated outcrop of the Torrelapaja Fm located south to Ciria village (see 428 Fig. 4A for location of the sampled point). U. Schudack and M. Schudack (2009) also report in a rich- 429 assemblage of Hauterivian-early Barremian freshwater ostracods, including different species of Cypridea, 430 Theriosynoecum, Fabanella, Mantelliana and Darwinula genera. As indicated above (section 6), the 431 analysis of the lowermost levels of Torrelapaja Fm in Valdelavieja and Las Cañadas logs has yielded a 432 microfossil assemblage with utriculi of Atopochara trivolvis var. ancora and A.t. var. triquetra varieties, 433 and Globator maillardii var. trochiliscoides (samples LC1 and CV1, Fig. 10). Moreover, the marly levels 434 found in the lower part of the Torrelapaja Fm in the Valdelavieja-Valdelatorre area has yielded an early 435 Barremian charophyte association with abundant Atopochara trivolvis var. triquetra (typical form) 436 (samples VT1, CV2 and CV3, Fig. 10). 437 According to Martín-Closas (1989) and Clemente (2010), the Torrelapaja Fm was deposited coeval to the 438 lower part of the Enciso Group (Fig. 14). However, the age of the Enciso Group has been debated (see 439 Martín-Closas, 1989; U. Schudack and M. Schudack, 2009; Clemente, 2010; Suárez-González et al., 2013; 440 Moreno-Azanza et al., 2016; Muñoz et al., 2020). The late Hauterivian-Barremian age range assigned by 441 Clemente (2010) for the Enciso Group is coherent with the presence of Atopochara trivolvis triquetra in 442 the Enciso locality (Schudack, 1987), the abundant late Valanginian–Barremian ostracod association 443 found in the unit (U. Schudack and M. Schudack, 2009), and the presence of the Barremian–Albian 444 dasycladalean Salpingoporella urladanasi in the Leza Fm, a lateral equivalent of the Enciso Group 445 including levels with marine fossils (Suarez- González et al., 2013). Recently, Muñoz et al. (2020) propose 446 a mid-Hauterivian to mid-Barremian age range for the Enciso Group based in cyclostratigraphy, with the 447 obtained astrochronological scale fitting within the available biostratigraphic data. 448 7.3. Synrift sequence 3: middle-upper Albian 449 In the Bigornia trough, the SS-3 consists of shales and sandy skeletal (oyster-rich) limestones, which 450 grades upwards to a terrigenous mudstone dominated succession with interbedded coal levels. Despite 451 the poor exposure of the SS-3 across the studied area, there is no evidence indicating the existence of a 452 significant sedimentary discontinuity (or angular unconformity) within this succession, that have been 453 assigned here to the Escucha Fm. However, previous work in Bigornia trough (Alonso and Mas, 1988, 454 1993) considered the presence of a sedimentary discontinuity between the lower (oyster-rich) and upper 455 (coal-rich) successions. The authors suggested an early Aptian age for the oyster-rich succession, based 456 in its tentative correlation to the shallow marine units found more than 120 km southwards to the 457 Torrelapaja Subbasin, in the Maestrazgo Basin. This early Aptian age assignment was also assumed in 458 latter works (e.g., Guimerà et al., 2004; Mas et al., 2004; Suarez-González et al., 2013). 459 There are few exposures of Lower Cretaceous marine units exposed close the Torrelapaja Subbasin. The 460 closest shallow marine succession of Grávalos is found 60 km north of Torrelapaja, in the footwall of the 461 North Cameros thrust. In Grávalos, a 50 m-thick mixed siliciclastic-carbonate succession with skeletal- 462 rich beds (oysters, foraminifera, serpulids, rudists, green algae, echinoderms) have yielded an association 463 of Albian benthic foraminifera with Flabellammina alexanderi and Haplophragmium sp. (Muñoz et al., 464 1997). According to these authors, this skeletal-rich succession is conformably overlain by the shales and 465 sandstones with coal levels typical of the middle-upper Albian Escucha Fm. As observed in Torrelapaja, 466 the shallow marine succession of Grávalos is also overlain by the postrift unconformity (Utrillas Fm). 467 The SS-3 of the Torrelapaja Subbasin is regarded here as time-equivalent to the Albian succession of 468 Grávalos, and is therefore proposed to be deposited around the middle-late Albian times (Fig. 14). The 469 middle-late Albian age proposed here for the SS-3 in the Torrelapaja Subbasin based on its correlation to 470 the closest marine unit found in an equivalent stratigraphic position is coherent with strontium isotopic 471 data obtained in our work. The isotopic analysis of three oyster shells (Exogyra) found in a yellowish 472 terrigenous mudstone interval within the lower part of the SS-3 (see Fig. 4B for location of the sampling 473 site) have yielded 87Sr/86Sr isotopes values of 0.707447, 0.707459 and 0.707460, respectively. Due to its 474 deposition in coastal environments, these values obtained from oyster shells may have abnormally high 475 values reflecting a relatively more radiogenic isotopic signal linked to freshwater input (e.g., Bryant et al., 476 1995). However, the significance of these strontium values is supported by the similar results obtained 477 from the three well-preserved shells analysed, which fit in turn the expected isotopic Cretaceous values. 478 Combining the age of the underlying Torrelapaja Fm (uppermost Hauterivian-lower Barremian) and of 479 the overlaying Utrillas Fm (uppermost Albian-middle Cenomanian: Alonso et al. 1993; García et al., 480 2004), and the global marine 87Sr/86Sr Cretaceous curve (Bralower et al., 1997; Denison et al., 2003; 481 McArthur et al., 2012), the obtained values are constrained in two different time intervals: late 482 Barremian-early Aptian and middle-late Albian respectively (Fig. 13D). However, the late Barremian-early 483 Aptian age for the SS-3 sequence is unlikely considering not only the major angular an erosive 484 unconformity with the underlying uppermost Hauterivian-lower Barremian SS-2 (Torrelapaja Fm), but 485 also the overall palaeogeography of Northeast Iberia during Early Cretaceous times (see discussion in 486 section 9). 487 488 8. TECTONO-SEDIMENTARY EVOLUTION OF THE TORRELAPAJA SUBBASIN: REGIONAL IMPLICATIONS 489 As shown in the previous section, the uppermost Jurassic-Lower Cretaceous record of the Torrelapaja 490 Subbasin is very discontinuous, with sedimentation stages during the Tithonian-middle Berriasian 491 (Bijuesca and Ciria formations), the latest Hauterivian-early Barremian (Torrelapaja Fm), and the middle- 492 late Albian (Escucha Fm), respectively. The angular unconformities developed between the synrift 493 sequences and the onlap geometries (see Fig. 8) should be explained in a context in which deformation 494 and block tilting associated to faulting also occurred during the periods without sedimentary record in 495 the basin. 496 The evolution of the successive synrift stages recorded in the Torrelapaja Subbasin was mostly controlled 497 by the activity of the three major NW-SE trending extensional faults described above: the southwest- 498 dipping Malanquilla Fault, the northeast-dipping Berdejo Fault and the northeast-dipping Carabantes 499 Fault System (Figs. 3 and 15). The Bigornia trough is located very close (< 1-2 km) to the South Cameros 500 Fault (section 1-1’; Fig 15). It has an asymmetric graben geometry, tilted towards the Berdejo Fault (i.e. 501 towards the southwest). The Bijuesca trough, however, has a significant halfgraben geometry, which is 502 indicative of the listric geometry of the border Carabantes Fault System. The asymmetry of both 503 structures suggests their link in depth with the basal detachment of the Malache and South Cameros 504 faults, i.e. with the southeast Cameros Basin. Numerous minor normal faults affect the synrift series, 505 usually in a NW-SE direction and, especially in the Bigornia graben, also in other directions. The latter 506 commonly have a NE-SW direction and dips to the northwest (i.e. towards the Cameros Basin) producing 507 traverse halfgrabens, as those located 1-3 km south of the Ciria village, that highly compartmentalized 508 the Bigornia graben (section 2-2’; Fig. 15). The mapping of these three major faults, along with the 509 identification and other minor scale synsedimentary normal faults allow reconstructing the extension of 510 depositional domains and depocentral areas of the Bigornia and Bijuesca troughs during the 511 sedimentation of SS-1, SS-2 and SS-3 (Fig. 16). 512 During the sedimentation of SS-1, the activity of the Carabantes Fault System resulted in the formation 513 of the Bijuesca halfgraben, which record more than 200 m of continental deposits in its southern 514 depocentral areas (Fig. 16A). This halfgraben structure is suggested by the overlap of the Utrillas Fm 515 (postrift unconformity) on increasingly older units (Ciria and Bijuesca formations and even Upper Jurassic 516 rocks) towards the northeast, that is, towards the Berdejo fault (Fig. 3). The conglomerates of the 517 Bijuesca Fm were sourced by the uplifted marine Jurassic rocks. Palaeocurrent data measured in Bijuesca 518 indicates a source area located to the south (Fig. 16A). The analysis of the nature of limestone clasts of 519 the conglomerates in the well exposed outcrop of Bijuesca reveals a predominance of clasts derived 520 from the erosion of the Middle-Upper Jurassic units in the lower part of the Bijuesca Fm, whereas Lower 521 Jurassic clasts dominate in the conglomeratic beds of the upper part of the unit. This trend can be 522 related to the progressive denudation of the marine Jurassic rocks exposed in the southern uplifted 523 areas (i.e. inverted vertical clast distribution or normal unroofing sequence; Colombo, 1994). It is 524 interesting to note that the areas that remained uplifted in the southern margin of the Bijuesca trough 525 during the sedimentation of SS-1 show a very large erosive incision on the marine Jurassic rocks, and the 526 postrift Utrillas Fm overlays the lowermost Jurassic units (see the outcrops south of Bijuesca in Fig. 3). 527 The combined activity of the Berdejo and Malanquilla faults resulted in the formation of the NW-SE 528 trending Bigornia graben. The composition of the clast found in the conglomerates of the Bijuesca Fm in 529 this graben also indicates a dominant source from the surrounding uplifted marine Jurassic rocks. 530 Palaeocurrent data points to dominance of a southern drainage area at the onset of the sedimentation 531 of SS-1, followed by a northern source during the sedimentation of the middle and upper part of the 532 Bijuesca Fm (Fig. 16A; see Sacristán-Horcajada et al. 2012). Compared to the Bijuesca halfgraben, 533 thickness distribution in Bigornia graben is very irregular due to the activity of a set of NE-SW trending 534 faults (Figs. 15 and 16A). Moreover, the graben was asymmetric, with maximum thickness (c. 350–400 535 m) measured in the hanging wall of the Malanquilla Fault, but with a thicker sequence expected to occur 536 in the hanging wall of the Berdejo Fault according to structural reconstruction (section 1-1’; Fig. 15). The 537 posrift Utrillas Fm and younger units cover the unit in this area and it prevents the corroboration of this 538 assumption. A 180 m-thick succession was measured in the Berdejo fault zone, but it is located in its 539 southwesternmost fault block, which only recorded a small amount of the displacement of the Berdejo 540 Fault. Such outcrop of the Bijuesca and Ciria formations close to the fault, together with other very close 541 located in the footwall of the fault, clearly point that the sedimentation likely encompassed the entire 542 Torrelapaja Subbasin during this stage, and that the Berdejo and minor intrabasinal faults were only 543 responsible for the changes in thickness of the unit. 544 The lacustrine-palustrine carbonates of the Ciria Fm shows a large expansion across the entire 545 Torrelapaja Subbasin (Fig. 9). Discrete terrigenous-clastic of sandstones and clast-supported 546 conglomerates intercalated within the palustrine-lacustrine limestones of the Ciria Fm in less subsident 547 areas of the southeastern Bijuesca through (see log CC1 in Fig. 9B) are interpreted as distal alluvial fan 548 deposits sourced by the uplifted areas by the Malanquilla Fault. 549 During the sedimentation of SS-2 (Torrelapaja Fm), a set of normal faults with variable orientation was 550 active in the Torrelapaja Subbasin (Fig. 16B). The Malanquilla and Berdejo faults were reactivated and 551 controlled the evolution of the Bigornia trough. The angular unconformity between SS-1 and SS-2 in the 552 southeastern Bigornia trough shows evidence of previous faults that were not active during SS-2 (Fig. 8). 553 According to cartographic data, the set of NE-SW faults that compartmentalized the northwestern 554 Bigornia trough during the previous SS-1 were not reactivated (Fig. 3). However, the activity of these 555 faults should not be ruled out, because a set of faults with variable orientation (E-W to N-S) controlled 556 the sedimentation in the southeastern Bigornia trough (Fig. 16B). The reactivation of the NE-SW faults 557 located to the southeast (near the locality of Malanquilla) probably caused the displacement of the local 558 depocentres associated with intrabasinal halfgrabens towards that direction along the Bigornia trough 559 (see section 2-2’: Fig. 15). In the southern Bijuesca through, the local sedimentation and preservation of 560 SS-2 has been related to some minor normal faults (see also Fig. 4C). 561 After the initial stage of irregular sedimentation at the onset of SS-2 (stage 1), there were two stages 562 with variations in depositional subenvironments, which can be partly linked to the tectonic activity (Fig. 563 12). Stage 2 records carbonate-dominated distal alluvial muddy flats (marlstones/calcareous mudstones) 564 with local lateritic soils and carbonate shallow lakes in central areas, and very local terrigenous input in 565 the northern and southern marginal areas. In contrast, Stage 3 encompasses a more terrigenous-clastic 566 and asymmetric system, characterized to the south by a middle-distal alluvial fan with sandstone and 567 conglomerate channels bearing both limestone (Jurassic) and quartzite (Paleozoic) clasts, and to the 568 central and norther parts by ephemeral braided streams of quartzite conglomerates and muddy flats 569 (siliceous mudstone). The increase of terrigenous-clastic supply form stage 2 to stage 3 can be related to 570 an increase of tectonic activity, with conglomerates sourced by nearby uplifted Mesozoic-Paleozoic rocks 571 (from the south-southeast) and the braided streams sourced from uplifted Paleozoic rocks located 572 eastwards to the Torrelapaja Subbasin (Fig. 16B). 573 The sedimentation of SS-3 (Escucha Fm) spreads over the northeastern marginal areas of the Bigornia 574 trough, with thickness around 50 m in the areas located close to the Malanquilla and Berdejo faults (Fig. 575 16C). The poor exposure of the unit does not allow to reach precisions on the synsedimentary fault 576 activity as in previous sequences. However, the existence of relatively thick accumulation of the coal- 577 bearing successions of the Escucha Fm south of Ciria (Vallehermoso locality: IGME, 1984) suggests the 578 reactivation of a new fault plane related to the Malanquilla Fault and located in the footwall of the 579 former one. There is no evidence of sedimentation of the SS-3 sequence in the Bijuesca trough where 580 the postrift Utrillas Fm unconformably overlay SS-1 or older marine Jurassic units (Fig. 3). 581 In the northwestern Bijuesca trough, SS-3 unconformably overlay with high angle (>30) the beds of the 582 Bijuesca and Ciria formations, as well as the NE-SW faults and halfgraben structures described for SS-1 583 south of Ciria (Figs. 3 and 15). Such geometrical disposition suggests the following evolutionary stages 584 (see section 1-1’; Fig. 15): (i) the overall tilting of the SS-1 and SS-2 and of the prerift sequence towards 585 the SW, (ii) an erosional stage that levels the structure, and (iii) the onset of the sedimentation of SS-3, 586 the latter being favoured by the activation of the new fault plane associated to the Malanquilla Fault. At 587 this stage, it is probably that the Bigornia trough could change in graben polarity, with the eastern 588 Malanquilla fault being in turn the master fault of the graben. Similar changes in polarity of faults have 589 been also described in the Maestrazgo Basin (Querol et al., 1992; Capote et al., 2002). The long period of 590 time between the deposition of SS-2 and SS-3 proposed in this work (Fig. 14) is coherent with such a 591 change in polarity in the Torrelapaja Subbasin. 592 To summarize, the three periods of sedimentation recorded in the Torrelapaja subbasin correlate well 593 with the periods of higher tectonic activity defined by subsidence analysis and regional data in the 594 Cameros and Maestrazgo basins for the Late Jurassic-Early Cretaceous rifting stage (Mas et al., 1993, 595 Salas et al., 2001; Liesa et al., 2006, 2019). This means that the record in this sub-basin is mainly 596 produced and preserved by the differential subsidence associated with the faults. Note how in many 597 cases the three synrift sequences are truncated and bounded by angular unconformities, and in turn are 598 truncated by the postrift unconformity. In fact, in many of the fault footwall blocks, the postrift Utrillas 599 Fm rests almost directly on the Jurassic prerift series (Figs. 3 and 15). This is coherent to the position of 600 this subbasin in a marginal area of sedimentation in relation to the depocentral area of the Cameros 601 Basin. 602 On the other hand, the complex geometry of the Torrelapaja Subbasin, mainly defined by two nearly 603 perpendicular fault sets acting simultaneously, greatly resembles what happens during the Late Jurassic- 604 Early Cretaceous rifting stage in the Cameros Basin and in the marginal subbasins of the Maestrazgo 605 Basin (Platt, 1990; Cortés et al., 1999; Liesa et al., 2006, 2018; Antolín-Tomás et al., 2007; Meléndez et 606 al., 2009; Aurell et al., 2016, 2018). Contemporary multi-directional normal fault activity points to a 607 regime of radial extension. The greater significance of faults in NW-SE direction with respect to those in a 608 NE-SW direction, which defines the main structuring of the Torrelapaja Subbasin in sedimentary troughs 609 (Bigornia and Bijuesca), with respect to those in a NE-SW direction suggests a direction of main NE-SW 610 extension and a secondary NW-SE extension, as it has also been proposed for the Cameros Basin from 611 the analysis of faults, calcite veins and magnetic susceptibility anisotropy (Guiraud and Séguret, 1984; 612 Marqués et al., 1996; García-Lasanta et al., 2014). 613 614 9. DISCUSSION: THE PALAEOGEOGRAPHY OF NORTHEAST IBERIA REVISITED 615 The data and review reported here have implications on the reconstruction of the overall 616 palaeogeography of the uppermost Jurassic–Lower Cretaceous Iberian Basin rift system, providing 617 arguments to precise previous reconstructions of Northeast Iberia. 618 The palaeogeographic maps of Figure 17 show the reconstruction around the early Berriasian, the early 619 Barremian and the middle Albian, thus for the three synrift sequences recorded in the Torrelapaja 620 Subbasin, respectively. The studied subbasin is located in the southeastern edge of the Cameros Basin, 621 relatively close to the northwestern Maestrazgo Basin (Fig. 1A). Figure 14 shows the equivalence 622 between the three synrift sequences recorded in the Torrelapaja Subbasin to those defined in the 623 marginal subbasins of the Maestrazgo Basin. It is noted that the stratigraphic gap associated to the 624 unconformity between the SS-1 and SS-2 in the Torrelapaja Subbasin fits a period of irregular and 625 discontinuous sedimentation both in the Cameros Basin (DS IV-V of Clemente, 2010), and in the 626 Maestrazgo Basin, which shows a gap of variable amplitude associated to the unconformity between the 627 major synrift sequences 1 (Tithonian–Berriasian) and 2 (Valanginian–lower Albian) defined in Liesa et al. 628 (2019). 629 9.1. Early Berriasian palaeogeography 630 In the Torrelapaja Subbasin, sedimentation around the Tithonian-Berriasian transition occurred in 631 alluvial fan systems, which grade upwards to the setting of carbonate palustrine-lacustrine environments 632 across the entire sedimentation areas during the Berriasian. 633 The depocentral areas of the Cameros basin during the Tithonian-middle Berriasian record the different 634 siliciclastic-carbonate formations of the up to 3,800 m-thick Tera and Oncala groups (Gómez-Fernández 635 and Meléndez, 1994). Around the Tithonian-Berriasian transition, the westernmost areas were 636 dominated by braided fluvial systems, that gradually evolved to meandering fluvial systems in the 637 western-central areas (Clemente, 2010). Northwards, these fluvial deposits graded progressively to 638 broad, low-gradient tidal flats traversed by shallow meandering channels. The laterally related 639 carbonate-evaporitic deposits found in the northeastern part of the basin of the lower-middle Berriasian 640 Oncala Group were deposited in saline mudflats, with large sulphate input derived from the episodic 641 incursion of marine waters (Quijada et al., 2013, 2020). Similar sulphur isotopic compositions recorded in 642 the carbonate-gypsum deposits of the Oncala Group and in the Basque-Cantabrian Basin support the 643 connection of the Cameros Basin with marine and transitional areas of the Basque-Cantabrian Basin 644 during Berriasian times (Quijada et al., 2013). The existence of marine incursions is further supported by 645 the presence of scarce miliolids in the eastern Cameros basin in the units deposited around the 646 Tithonian-Berriasian transition: in the Matute Fm (upper Tera Group, DS-II; Fig. 14) and in the upper 647 Oncala Group (Gómez-Fernández and Meléndez, 1994). 648 In the southeastern margin of the Cameros Basin, including the Torrelapaja Subbasin, the abundance of 649 the charophytes Porochara and Mesochara found in the Ciria Fm suggests the possible episodic setting of 650 brackish waters (Martín-Closas, 1989). The presence of brackish waters around this marginal area could 651 be related to ephemeral marine influence sourced from the north (Basque-Cantabrian Basin). The overall 652 palaeogeography of the Iberian Basin rift system during the Berriasian (Fig. 17A) with the marine 653 sedimentation areas confined to the eastern Maestrazgo Basin (e.g., Aurell et al., 2016, 2019b; Bádenas 654 et al., 2004, 2018; Liesa et al., 2019), makes unlikely an alternative marine source from the Tethysian 655 realm. Also of interest are the lacustrine-palustrine carbonates found eastwards to the Torrelapaja 656 Subbasin, in Ricla (Fig. 17A), which also include abundant Porochara and Mesochara (Martín-Closas, 657 1989). As proposed by Salomon (1982) these carbonates are regarded here as time counterparts of the 658 Berriasian Ciria Fm. However, this is a tentative correlation, because the recorded charophyte 659 association of Ricla does not provide conclusive information about its age (Martín-Closas, 1989; Soria et 660 al., 1995). 661 9.2. Early Barremian palaeogeography 662 During the early Barremian, most of the Cameros basin was the site of continental sedimentation (Fig. 663 17B). The fluvial systems that dominated the sedimentation in the south-central part of the basin 664 changed towards the northwest to small carbonate lakes, and towards the northeast to a siliciclastic and 665 carbonate-dominated continental setting (Clemente, 2010). Assuming an early Barremian age for the 666 Leza Fm (see discussion above), evidences of marine influence coeval to the sedimentation of the SS-2 667 would be recorded in the northeastern edge of the Cameros Basin, with the relatively abundant 668 presence of dasycladaleans, echinoderms and miliolids in some carbonate levels. The Leza Fm was 669 deposited in a system of coastal wetlands with both freshwater and seawater influence, laterally related 670 to the fluvio-lacustrine deposits towards the south (Suarez-González et al., 2013). Further evidence of 671 marine influence around the earliest Barremian is indicated by the presence of debris of echinoderms in 672 the siliciclastic-dominated succession of the Enciso Group logged close to Navalsaz village (Muñoz et al., 673 2020; see Fig. 17B for location). 674 The discussion about the provenance of the episodic marine incursions to explain the presence of marine 675 skeletal-rich levels in the Enciso Group in the northeastern Cameros Basin can be further approached 676 with the available regional data. Lower Barremian deposits found in the Aguilón Subbasin (north to the 677 Maestrazgo Basin, Fig. 17B) correspond to the ostracod-rich lacustrine deposits of the Aguilón Fm (Fig. 678 14). In this unit, with the exception of a few Fabanella boloniensis (allowing more saline brackish water 679 environments), all identified species of ostracods indicates freshwater environments (U. Schudack and 680 M. Schudack, 2009). Further south, in the Oliete Subbasin, the presence of oyster-rich limestones in the 681 middle part of the Blesa Fm indicates the episodic marine connection with the open-marine areas of the 682 Maestrazgo Basin during the early Barremian (Fig. 17B; Aurell et al., 2018). However, there is no data 683 supporting that these marine incursions could reach the sedimentary domains located further north, in 684 the Aguilón Subbasin or in the eastern Cameros Basin. Similarly, the Artoles Fm in the Galve Subbasin 685 represented sedimentation in coastal to shallow marine environments, whereas towards the northwest, 686 in the Las Parras Subbasin, palustrine-lacustrine marls and limestones, containing fresh-water ostracods 687 and charophytes developed (Camarillas Fm: Fig. 14; Liesa et al., 2019). Moreover, considering that the 688 Barremian–Aptian marine facies are confined to the eastern areas of the Maestrazgo Basin (e.g., García, 689 1982; Liesa et al., 2019), the connection between the Tethys and the Cameros Basin during this time 690 span is unlikely, and the presence of the marine levels found in the northeastern Cameros Basin (Enciso 691 Group) can be satisfactory explained as exclusively related to northern marine incursions (Fig. 17B). 692 9.3. Middle Albian palaeogeography 693 The middle-late Albian successions of the Escucha Fm recorded in the Bigornia trough indicates the 694 episodic setting of coastal marine sedimentary domains (with oysters, echinoderms and serpulids) in the 695 southeastern marginal areas of the Cameros Basin. The coeval successions of Grávalos, located in the 696 footwall of the North Cameros thrust (Fig. 17C), include more open marine intervals, with abundant 697 rudists. According to Muñoz et al. (1997), there is a gradual transition between these shallow marine 698 facies and the coal-rich transitional successions typical of the Escucha Fm. 699 Following Clemente (2010), the equivalent unit to the Escucha Fm in the western Cameros Basin is the 700 upper part of the Salas Group, a largely progradational fluvial system with evidence of aeolian facies, 701 unconformably overlain by the postrift sandstones of the Utrillas Fm. Terrigenous input of this fluvial 702 system was sourced from the western uplifted Iberian Massif, and drained the basin towards the north- 703 northeast, passing gradually to a tide-influenced coastal plain. According to Clemente (2010), the middle- 704 upper part of the Salas Group in the Soria-Abejar area includes relatively thick intervals of facies with 705 inclined heterolithic strata and coal of possibly tidal origin. Marine incursions in the eastern Cameros 706 Basin were sourced from the north (Muñoz et al., 1997; Clemente, 2010). An alternative source from the 707 southeastern Tethysian domain is unlikely, since the coastal marine sedimentation during the Albian in 708 the Maestrazgo Basin was confined south to the Oliete Subbasin, in its eastern depocentral areas (Fig. 709 17C; Querol et al., 1992; García et al., 2004; Liesa et al., 2019). 710 711 10. CONCLUSIONS 712 The review of the stratigraphy, sedimentology, structural evolution and vertebrate fossil record of the 713 synrift deposits of the Torrelapaja Subbasin (southeastern Cameros Basin) presented in this study has 714 provided the following main findings: 715 1- The evolution of the uppermost Jurassic-Lower Cretaceous Torrelapaja Subbasin was mostly 716 controlled by the activity of the three major NW-SE trending extensional faults: Malanquilla Fault 717 (southwest-dipping), Berdejo Fault (northeast-dipping) and Carabantes Fault System (northeast-dipping). 718 The subbasin was longitudinally subdivided into the Bigornia and Bijuesca troughs by the Berdejo Fault. 719 The Bigornia trough is located very close to the South Cameros Fault and it recorded the most complete 720 and thicker synrift sedimentary succession. 721 2- Discontinuous activity of the major NW-SE trending faults combined to other minor faults with 722 variable orientation (around NE-SW trending) resulted in an irregular uppermost Jurassic-Lower 723 Cretaceous sedimentary record. The complex geometry of the Torrelapaja Subbasin reconstructed in this 724 work is defined by this two nearly perpendicular fault sets acting simultaneously. The greater significance 725 of faults in NW-SE suggests a direction of main NE-SW extension and a secondary NW-SE extension, as 726 has also been previously proposed for the Cameros Basin. 727 3- The sedimentary record of the Torrelapaja Subbasin consist of three synrift sequences (SS-1, SS-2 and 728 SS-3) bounded by major unconformities. These unconformities are related to the reactivation of 729 different sets of faults during the different stages of evolution of the subbasin. The Tithonian–middle 730 Berriasian SS-1 (Bijuesca and Ciria formations) occurs across the entire Torrelapaja Subbasin, whereas 731 the uppermost Hauterivian–lower Barremian SS-2 (Torrelapaja Fm) and the middle–upper Albian SS-3 732 (Escucha Fm) are recorded with significant thickness only in the northern part of the subbasin, in the 733 Bigornia trough. 734 4- The large sedimentary record of SS-1 occurs in the Bijuesca trough (up to 220 m) and in the 735 northwestern Bigornia trough, where the presence of NE-SW trending faults involved the presence of 736 highly subsident blocks, with up to 350–400 m-thick deposits. Sedimentation of SS-1 occurred in alluvial 737 fan systems, sourced from the uplifted basin margins, exposing the marine Jurassic carbonate rocks. The 738 progressive degradation of the relief favoured the expansion of the carbonate palustrine to lacustrine 739 environments across the entire sedimentation areas during the early-middle Berriasian. The new 740 discovered vertebrate fossil site of La Atalaya (Bijuesca trough) includes large sized sauropods and 741 crocodylomorphs preserved in palustrine facies, and was most probably formed around the Tithonian- 742 Berriasian transition. 743 5- The boundary between SS-1 and SS-2 is a widespread unconformity associated to an upper Berriasian- 744 lower Hauterivian stratigraphyc gap. The thickest record of SS-2 (Torrelapaja Fm) found in the 745 southeastern part of the Bigornia trough (up to 80 m) was mostly controlled by the activity of the 746 Malanquilla and Berdejo NW-SE trending faults, combined to a set of small-scale faults with variable 747 orientations around NW-SE. A locally deep-incised palaeokarst developed on top of the Berriasian 748 lacustrine carbonates was filled by a few dm-thick multiphase levels of muddy distal alluvial facies 749 around the Hauterivian-Barremian transition. These facies include the new discovered vertebrate fossil 750 sites of Corrales de las Cañadas, Corrales de Valdelavieja and Valdelatorre, with a dinosaur-dominated 751 macrovertebrate record of sauropod, theropod and ornithopod remains. After this stage of condensed 752 and irregular sedimentation, a second early Barremian stage of muddy distal alluvial plains with 753 paleosoils and Fe-pisoids as well as palustrine-shallow lacustrine carbonate systems developed. At the 754 third stage, increased tectonic activity involved larger terrigenous-clastic input sourced from the 755 southeast, and the development of middle-distal alluvial systems, and distal mud flats with small 756 carbonate ponds in the central part of the Bigornia trough. 757 6- The SS-3 (Escucha Fm) includes shales and intercalated sandy-skeletal limestones with abundant 758 oysters and plant debris. This unit is assigned here to the middle-upper Albian based in regional 759 correlation and strontium isotopic data. The widespread presence of oysters and other marine skeletal 760 debris (serpulids, echinoderms) indicates the first marine incursion in the studied basin, with marine 761 waters sourced from the north (Bay of Biscay domain). The overall palaeogeography of the Iberian Basin 762 rift system during the Early Cretaceous reviewed and updated here makes unlikely an alternative marine 763 source from the southeast (Tethysian realm) as suggested in previous works. Accordingly, the results 764 presented here might have further implications for the understanding of the overall evolution of the 765 latest Jurassic-Early Cretaceous Iberian rifting, as clarifying the distribution in time and space of 766 Thetysian and northern affinities of the different paleogeographical domains, and the causes and 767 processes laying behind. 768 769 Acknowledgments 770 This study was subsidized by the Spanish Ministerio de Economía y Competitividad-ERDF (Project 771 CGL2017-85038-P), the Spanish State Research Agency (Project PID2019-108705GB-I00), as well as by 772 the Aragón Regional Government and the European Regional Development Fund (research groups 773 E18_20R Aragosaurus: recursos geológicos y paleoambientes and E32_20R Geotransfer: investigación 774 geológica para la ciencia y la sociedad). We thank Prof. Carles Martín-Closas for the assistance in the 775 charophyte determination. We also acknowledge the suggestions provided by the two reviewers 776 (professors Marian Fregenal-Martínez and Bruno Granier) that helped to improve the quality of the 777 original manuscript. We also appreciate the technical assistance of the Servicio General de Apoyo a la 778 Investigación-SAI, Universidad de Zaragoza. DC is supported by the Beatriu de Pinós postdoctoral 779 programme (BP2017-00195) of the Government of Catalonia’s Secretariat for Universities and Research 780 of the Ministry of Economy and Knowledge. 781 782 REFERENCES 783 Allix, P., Burnham, A., Fowler, T., Herron, M., Kleinberg, R., Symington, B. (2011): Coaxing oil from Shale. 784 Oilfield Review 22 (4), 4–15. 785 Alonso, A., Mas, J. R. (1988): La transgresión Aptiense al sur del Moncayo (límite de las provincias de 786 Soria y Zaragoza). II Congreso geológico de España Vol 1, Granada: p. 11–15. 787 Alonso, A., Mas, J.R. 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(1997): Caracterización estratigráfica y 926 sedimentológica del Albiense marino del borde Norte de la Sierra de Cameros. Implicaciones 927 Paleogeográficas. Cuadernos de Geología Ibérica 22, 139–163 928 Muñoz, A., Angulo, A., Liesa, C.L., Luzón, M.A., Mayayo, M.J., Pérez, A., Soria, A.R., Val, V., Yuste, A. 929 (2020). Periodicidad climática y datación astrocronológica del Grupo Enciso en la Cuenca oriental de 930 Cameros (N de España). Boletín Geológico y Minero, 131, 2, doi. 10.21701/bolgeomin.131.2.003. 931 Navarro-Vázquez, D. (coord) (1991): Mapa Geológico de España, 1:50000. Num 380 (Borobia). Instituto 932 Tecnológico Geominero de España, Madrid. 933 Pérez-Lorente, F. (2015). Dinosaur footprints and trackways of La Rioja. Indiana University Press. 934 Platt, N.H. (1990). 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(2011): Sedimentología de sucesiones sinrift 954 tempranas en un semigraben marginal de un rift extensional: la Cuenca de Bijuesca, Jurásico superior 955 de la Cordillera Ibérica (Zaragoza, España). Geogaceta, 50-2: 121–124. 956 Sacristán-Horjacada, S., Carrasco, A., Mas, R., Arribas, M.E. (2012): Comparación del registro 957 estratigráfico de dos cubetas satélites aso- ciadas a un sistema de rift: los surcos de Bijuesca y 958 Bigornia (SE de la Cuenca de Cameros). Geo-Temas 13 (2): 155-158 (02_108-111 in CD). 959 Salas, R., Guimerà, J., Mas, R., Martín-Closas, C., Meléndez, A., Alonso, A. (2001): Evolution of the 960 Mesozoic Central Iberian Rift System and its Cainozoic inversion (Iberian chain). In: P.A. Ziegler, W. 961 Cavazza, A.H.F. Robertson, S. Crasquin-Soleau (eds.), Peri-Tethys Memoir 6: Peri-Tethyan rift/wrench 962 basins and passive margins. Mémoires du Musée nat. Hist. naturelles de Paris 186, 145–185. 963 Salomon, J. (1982): Cameros-Castilla: El Cretácico Inferior. In A. García (Ed.), El Cretácico de España (pp. 964 345–387). Madrid: Univ. Complutense de Madrid. 965 San Román, J., Aurell, M. (1992): Palaeogeographical significance of the Triassic–Jurassic unconformity in 966 the north Iberian basin (Sierra del Moncayo, Spain). Palaeogeography, Palaeoclimatology, 967 Palaeoecology, 99, 101–117. 968 Schudack, M. (1987): Charophyten flora und fazielle Entwicklung der Grenzschichten mariner Jura- 969 Wealden in den Nordwestlichen Iberi- schen Ketten (mit Vergleichen zu Asturien und Kantabrien). 970 Palaeontographica Abteilung B 204, 1–180. 971 Schudack, U., Schudack, M. (2009): Ostracod biostratigraphy in the Lower Cretaceous of the Iberian 972 chain (Eastern Spain). Journal of Iberian Geology 35, 141–168. 973 Soria, A.R., Martín-Closas, C., Meléndez, A., Meléndez, N., Aurell, M. (1995): Estratigrafía del Cretácico 974 Inferior del sector central de la Cordillera Ibérica. Estudios Geológicos 51, 141–152. 975 Suárez-González P, Quijada IE, Benito MI, Mas R (2013): Eustatic versus tectonic control in an intraplate 976 rift basin (Leza Fm, Cameros Basin): chronostratigraphic and paleogeographic implications for the 977 Aptian of Iberia. Journal of Iberian Geology 39: 285–312. 978 Torcida Fernández-Baldor, F., Canudo, J.I., Huerta, P., Moreno-Azanza, M., Montero, D. (2017): 979 Europatitan eastwoodi, a new sauropod from the Lower Cretaceous of Iberia in the initial radiation of 980 somphospondylians in Laurasia. PeerJ, 5:e3409. 981 FIGURES 982 983 Fig. 1. - (A) Geological location of the Torrelapaja Subbasin. The map of the Iberian Peninsula shows the 984 distribution of Mesozoic outcrops and the location of three main uppermost Jurassic-Lower Cretaceous 985 sedimentary domains of Northeast Iberia: Maestrazgo (Ma), Cameros (Ca) and Basque-Cantabrian (BC) 986 basins; (B) Geological restored section at the end of Mesozoic extension through the eastern part of the 987 Cameros Basin (see dashed line in A for location). Modified from Guimerà et al. (2004), with 988 reconstruction of the Torrelapaja Subbasin based on data exposed in this work. 989 990 991 992 993 994 Fig. 2. - Summary of the stratigraphy of the Torrelapaja Subbasin. Major discontinuities D1–D5 separate 995 the successive synrift and postrift Mesozoic sequences. Abbreviated names of units of right column refer 996 to those used in the geological mapping of Figure 4. The studied synrift sequences (SS) shadowed in gray 997 in the central column are very variable in thickness. 998 999 1000 1001 Fig. 3. - Geological mapping of the area including the Torrelapaja Subbasin. The mapping of the squared 1002 areas A, B and C is enlarged in Figure 4. 1003 1004 1005 Fig. 4. – Detailed geological mapping of some key areas (see Figs. 2 and 3 for legend of stratigraphic units 1006 and location). (A) Northern area: the orange stars locate in the abandoned coal mines in the upper 1007 Escucha Fm; the two green stars indicates the sampling points for charophytes of Martín-Closas (1989) in 1008 the Ciria and Torrelapaja formations respectively; (B) Central area: the black arrows indicate the location 1009 of La Cañada (LC), Valdelatorre (VT) and Valdelavieja (VJ) logs in the Torrelapaja Fm; the red squares 1010 indicate the new fossil sites of Corrales de Las Cañadas (CC), Valdelatorre (VT) and Corrales de 1011 Valdelavieja (CV); the pink squares correspond to the fossil sites BJ1 and BJ5 of Royo-Torres et al. (2012), 1012 the red squares indicate the new dinosaur fossil sites of Corrales de Las Cañadas (LC), Valdelatorre (VT), 1013 Valdelavieja (VJ) in the Torrelapaja Fm (see Fig. 10 for their stratigraphic location); the green star in B is 1014 the sampling point for the Exogyra shells used in the strontium analysis of the Escucha Fm; (C) Southern 1015 area with location of the Bijuesca (BJ) log and the new discovered fossil site of La Atalaya (LA) in the 1016 Bijuesca Fm (see red square). 1017 1018 1019 1020 Fig. 5. - The synrift sequence 1 in the Bijuesca trough. (A) General view of the Bijuesca outcrop, showing 1021 the distribution of units. The left part shows the angular unconformity with the Utrillas Fm. The yellow 1022 star locates the La Atalaya fossil site in the topmost levels of the Bijuesca Fm; (B) Fining-upward 1023 sequence in the upper Bijuesca Fm, ending with nodular/brecciated limestones with root traces. The 1024 yellow star indicates the carbonate level including La Atalaya fossil site (see Fig. 10 for its stratigraphic 1025 location); (C) Detail of the paraconformity between the lower Kimmeridgian reef limestones of the 1026 Torrecilla Fm and the conglomerates, sandstones and mudstones of the Bijuesca Fm; (D) Large-sized limb 1027 bone fragment assigned to Sauropoda indet floating in a nodular/brecciated limestones in La Atalaya 1028 site; (E) Large-sized caudal vertebra assigned to Sauropoda indet. encased in burrowed marls in La 1029 Atalaya site; (F) A fining-upward sequence from conglomerates to sandstones to red mudstones in the 1030 upper Bijuesca Fm; (G) Close view of clast-supported conglomerates with poorly rounded Jurassic 1031 limestone clasts with normal gradation in the middle part of the Bijuesca Fm. 1032 1033 1034 Fig. 6. - The synrift sequence 2 in the outcrops located around Valdelavieja-Valdelatorre logs. (A) Highly 1035 irregular paleokarst developed on top of the Ciria Fm in Valdelavieja log, including the fossil site of CV. 1036 The overlying level (white star) includes the samples CV-2 and CV-3 (see fig. 10); (B) The infill of the karst 1037 cavities in Valdelavieja has yield two theropod? vertebrae (see white arrows) and other remains; (C) 1038 Rippled sandstones in the middle part of the Torrelapaja Fm; (D) General view of the outcrop of 1039 Valdelatorre exposing the ochre marlstones/calcareous mudstones of the lower part of the Torrelapaja 1040 Fm. The yellow star indicates the location of the Berdejo-1 (BJ-1) fossil site of Royo-Torres et al. (2012); 1041 (E) Close view of the grain-supported conglomerates with quartzite clasts and normal gradation found in 1042 the middle part of the Torrelapaja Fm in the Valdelavieja log; (F) Close view of the tufa level with 1043 abundant debris of coated plant stems exposed in the upper part of the Torrelapaja Fm in the 1044 Valdelatorre log. 1045 1046 1047 1048 1049 Fig. 7. - Field views of Las Cañadas log. (A) Large karst cavity developed on top of the Ciria Fm filled by 1050 reddish mudstones; (B) Close view of the sauropod humerus recovered in the paleokarstic cavity of Las 1051 Cañadas; (C) General view of the outcrop of Las Cañadas; (D) Red mudstones with hydromorphic soils of 1052 the upper part of the Torrelapaja Fm in Las Cañadas log; (E) Boundary between SS-2 (Torrelapaja Fm) and 1053 SS-3 (Escucha Fm) in Las Cañadas outcrop; (F) Sandy skeletal limestone rich in oyster shells typical of the 1054 lower part of the Escucha Fm. 1055 1056 1057 Fig. 8. – Oblique aerial view (above) and outcrop image (below) of two examples showing the angular 1058 unconformity between SS-1 (Ciria Fm) and SS-2 (Torrelapaja Fm) in the southeastern part of the Bigornia 1059 trough. The example of the right includes the Corrales de Las Cañadas fossil site. Note as the angular 1060 unconformity fossilizes decametric-scale normal faults affecting the Ciria Fm limestones, and the lower 1061 Torrelapaja Fm beds onlap the unconformity. 1062 1063 Fig. 9. - Sedimentological features of the Bijuesca and Ciria formations. (A) Stratigraphic log indicating 1064 the facies distribution of the Bijuesca and Ciria formations in Bijuesca locality (redrawn and slightly 1065 modified from Sacristan-Horcajada et al., 2011; see BJ in Fig. 4C for location), and the location of La 1066 Atalaya fossil site; (B) Stratigraphic log indicating the facies distribution of the Ciria Fm in Las Cañadas 1 1067 log (LC1; see Fig. 4B for location); (C-D) Thin section images in plane-polarized light of limestone facies of 1068 the Ciria Fm: (C) palustrine limestones with charophytes and fenestral porosity (see 1); and (D) oncolitic 1069 limestones with cm-thick oncoids with charophytes in the nuclei (see 1). 1070 1071 Fig. 10. - Sedimentological features of the Torrelapaja Fm. (A) Stratigraphic logs indicating the facies 1072 distribution of the Torrelapaja Fm (see Fig. 4B for location). The three sedimentary stages differentiated 1073 and the location of the fossil sites of Corrales de Valdelavieja (CJ), Valdelatorre (VT), Corrales de Las 1074 Cañadas (CC) and Berdejo-1 (BJ-1) are also indicated; (B) Mineralogical composition of muddy facies of 1075 the unit (tertiary diagram adapted from Allix et al., 2011). 1076 1077 1078 1079 1080 1081 Fig. 11. Thin sections images in plane-polarized light of limestone facies of the Torrelapaja Fm. (A) 1082 Intraclastic/litoclastic facies with quartz sand and quartzite lithoclasts (Paleozoic: see 1), limestone 1083 (Jurassic) lithoclasts (see echinoid spine in 2 and ooids in 3), intraclasts of bioclastic facies (see 4), oncoid 1084 fragments (see 5) and vertebrate remains (see 6); (B–D) Lacustrine bioclastic limestones, including (B) 1085 bivalve and gastropod packstone and (C) bioturbated ostracod wackestone/packstone, with 1086 accumulation of skeletal debris produced by hydrodynamic sorting; and (D) ostracod and charophyte 1087 wackestone; (E) Fenestral bioclastic limestone with ostracods and charophytes formed in palustrine 1088 areas. Notice fenestral porosity (see 1), charophytes (see 2) and oncoid fragments (see 3); (F-G) Tufa 1089 limestones including (F) oncolitic packstones/grainstones with entire and broken oncoids, with bioclastic 1090 and intraclastic cores and cortices formed by sub-mm to mm alternation dark micritic laminae (see 1), 1091 and porous micritic laminae with microbial filaments perpendicular to laminae (see 2), intraclasts of 1092 stromatolites (see 3) and coated plant stems (see 4); and (G) phytoclastic packstones big clasts of coated 1093 plant stems and stromatolites, in an packstone matrix of smaller intraclasts and oncoid fragments. 1094 1095 1096 Fig. 12. Palaeoenvironmental reconstruction of facies of sedimentary stages 1 to 3 of the Torrelapaja Fm 1097 (see Fig. 10 for legend of facies). 1098 1099 1100 1101 Fig. 13. (A) Sedimentological features of the Escucha Fm (SS-3) in the Valdelavieja 3 log (see VJ3 in Fig. 4B 1102 for location); (B-C) Thin sections images in plane-polarized light of limestone facies, including (B) sandy 1103 blioclastic limestones, with abundant oysters and gastropods, intraclasts of muddy limestones (see 1) 1104 and sandstones (see 2) and carbonaceous material (see 3); and (C) bivalve sandy limestones, with 1105 accumulated debris of oysters, and some serpulids (see 1) and carbonaceous material (see 2). (D) 1106 Strontium isotopic curve of McArthur et al. (2012) during Barremian–Albian (in light gray) indicating the 1107 interval comprising the three values obtained from the Escucha Fm (withe diamonds, left part). 1108 Considering the time constrains provided by the Torrelapaja and Utrillas formations, the obtained 1109 isotopic values are compatible with two time intervals (see dark grey surface). However, regional data 1110 and overall palaeogeography of northeast Iberian clearly point to a middle-late Albian age for the 1111 Escucha Fm (see further explanation and discussion in text). 1112 1113 1114 Fig. 14. Proposed equivalence between the synrift sequences recorded in the Torrelapaja Subbasin and 1115 those recorded in the eastern Cameros Basin (mostly based in Clemente, 2010) and the subbasins of the 1116 Western Maestrazgo Basin (compiled from Aurell et al, 2018, 2019b and Liesa et al., 2019; see fig. 1 for 1117 location of basins and subbasins). 1118 1119 1120 1121 1122 Fig. 15. Idealized geological cross-sections showing the structure of the Torrelapaja Subbasin at the time 1123 of postrift sedimentation (see map for location). 1-1': Transverse view of the Torrelapaja Subbasin 1124 showing the structure of the Bigornia and Bijuesca troughs. 2-2': Longitudinal section along the Bigornia 1125 trough. Note that the NE-SW Cenozoic shortening has not been restored. 1126 1127 1128 Fig. 16. - Reconstruction of the Bijuesca and Bigornia troughs (Torrelapaja Subbasin) located south of the 1129 South Cameros Fault (inset) during the sedimentation of synrift sequences (SS) 1, 2 and 3 (maps A, B and 1130 C respectively). Specific data of thickness measured in different localities are indicated. Arrows in A and B 1131 indicates palaeocurrent data (the data in SS-1 taken form Sacristán-Horcajada et al., 2012). Note that 1132 maps represent the present-day locations of structures and outcrops, that is without the restoration of 1133 the NE-SW Cenozoic shortening. 1134 1135 1136 Fig. 17. Distribution of main sedimentary domains of Northeast Iberia around (A) the early Berriasian, (B) 1137 the early Barremian and (C) the mid-Albian. Palaeogeography of the Basque-Cantabrian Basin taken from 1138 García (1982), García-Mondejar (1990) and Pujalte et al. (2004). Cameros Basin compiled from Muñoz et 1139 al. (1997), Clemente (2010), Quijada et al. (2013) and Suárez-Gonzalez et al. (2013). Maestrazgo Basin 1140 based on Querol et al. (1992), Aurell et al. (2018, 2019b) and Liesa et al. (2019).