Shore platform and cliff notch transitions along the La Paz Peninsula, southern Baja, Mexico
Trenhaile, Alan S. (University of Windsor (Ontario, Canadà). Department of Earth and Enviromental Sciences)
Porter, N. I. (University of Windsor (Ontario, Canadà). Department of Earth and Enviromental Sciences)
Prestanski, K. (University of Windsor (Ontario, Canadà). Department of Earth and Enviromental Sciences)

Fecha:	2015
Resumen:	Increasing exposure to wave action produces a northerly transition from high tidal notches to shore platforms in the andesitic lahar deposits of the La Paz Peninsula, southern Baja, Mexico. Twenty-four notches were surveyed and wear pins were cemented into the apex of each notch. Thirty-six transverse micro-erosion meter (TMEM) stations were installed on three surveyed platforms. Field measurements were made over a 2. 5 year period. The wear pins suggested notch backwearing (horizontal erosion) is <2mm yr-1. The shore platforms were fairly narrow (a few tens of metres) and steeper (1º) than most platforms in similar microtidal environments, reflecting a weak wave environment and resistant rocks. Mean TMEM downwearing (vertical erosion) rates for each of the three platforms ranged from 0. 14mm yr-1 to 0. 42mm yr-1. There was a good relationship between notch height (difference in elevation between the floor and the roof at the front of the notch) and exposure to wave action, but notch depth is time-dependent and the relationship with exposure was not statistically significant. Notch height was also related to the orientation and wave fetch of the site. Field evidence suggested that the notches were not produced by bioerosion or chemical weathering but by alternate wetting and drying or salt weathering from high tidal immersion and wave-generated splash and spray. Coastal morphology is fairly well adjusted to present sea level although notch occurrence in the upper portion of the high tidal zone suggests that there is slow tectonic uplift in this region.
Derechos:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, sempre i quan aquestes es distribueixin sota la mateixa llicència que regula l'obra original i es reconegui l'autoria.
Lengua:	Anglès
Documento:	Article ; recerca ; Versió publicada
Materia:	Notches ; Shore platforms ; Erosion rates ; Wave exposure ; Weathering
Publicado en:	Geologica acta, Vol. 13 Núm. 2 (June 2015) , p. 167-180, ISSN 1696-5728

Adreça alternativa: https://raco.cat/index.php/GeologicaActa/article/view/294815
Adreça alternativa: https://revistes.ub.edu/index.php/GEOACTA/article/view/GeologicaActa2015.13.2.7
DOI: 10.1344/GeologicaActa2015.13.2.7

14 p, 2.5 MB

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