Lower Cretaceous Alisitos Formation at Punta San Isidro: Coastal sedimentation and volcanism

Lower Cretaceous Alisitos Formation at Punta San Isidro: Coastal sedimentation and volcanism

The Lower Cretaceous (Aptian-Albian) Alisitos Formation is well exposed at Punta San Isidro and adjacent sea cliffs on the Pacific shores of Baja California near Eréndira, Mexico. Continuous coastal outcrops define a local stratigraphic succession less than 100 m in total thickness, including repeti...

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Auteurs principaux: Payne, JL, Jhonson, ME, Ledesma-Vázquez, J
Format: Online
Langue:eng
Publié: Iniversidad Autónoma de Baja California 2004
Accès en ligne:https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/179
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id oai:cienciasmarinas.com.mx:article-179
record_format ojs
institution Ciencias Marinas
collection OJS
language eng
format Online
author Payne, JL
Jhonson, ME
Ledesma-Vázquez, J
spellingShingle Payne, JL
Jhonson, ME
Ledesma-Vázquez, J
Lower Cretaceous Alisitos Formation at Punta San Isidro: Coastal sedimentation and volcanism
author_facet Payne, JL
Jhonson, ME
Ledesma-Vázquez, J
author_sort Payne, JL
title Lower Cretaceous Alisitos Formation at Punta San Isidro: Coastal sedimentation and volcanism
title_short Lower Cretaceous Alisitos Formation at Punta San Isidro: Coastal sedimentation and volcanism
title_full Lower Cretaceous Alisitos Formation at Punta San Isidro: Coastal sedimentation and volcanism
title_fullStr Lower Cretaceous Alisitos Formation at Punta San Isidro: Coastal sedimentation and volcanism
title_full_unstemmed Lower Cretaceous Alisitos Formation at Punta San Isidro: Coastal sedimentation and volcanism
title_sort lower cretaceous alisitos formation at punta san isidro: coastal sedimentation and volcanism
description The Lower Cretaceous (Aptian-Albian) Alisitos Formation is well exposed at Punta San Isidro and adjacent sea cliffs on the Pacific shores of Baja California near Eréndira, Mexico. Continuous coastal outcrops define a local stratigraphic succession less than 100 m in total thickness, including repetitious tuff, sandstone and conglomerate units interbedded with discontinuous limestone beds rarely more than 2.5 m thick. The limestone beds are biostromal units that include scattered oysters and/or corals, as well as units dominated by the rudistid bivalve, Caprinuloidea perfecta. Two distinctive conglomerate units are composed of andesite cobbles colonized by encrusting oysters in a quasi rocky-shore setting. One sandstone unit includes abundant fossil wood with tree limbs up to 55 cm long and 5 cm in diameter. Proximal volcanic activity is indicated by a series of dikes that cut through pyroclastic beds and lead to a 10-m thick andesitic flow that caps the succession at Punta San Isidro. Compared with thicker intervals of the Alisitos Formation elsewhere in Baja California that are dominated by andesitic flows and offshore limestone, the Punta San Isidro sequence offers a window on a back-reef environment adjacent to a paleoshore that received pyroclastic lahars from a terrestrial origin or mass flows from shallow submarine explosions. Recovery of marine life and the renewal of a carbonate substrate followed successive episodes of volcanism and massive erosion along an active coastline. This scenario is very different from depositional processes of the Upper Cretaceous (Campanian-Maastrichtian) Rosario Formation that cannibalized and subsequently formed a regional unconformity against tilted Alisitos strata with substantial topographic relief in the Eréndira region.
publisher Iniversidad Autónoma de Baja California
publishDate 2004
url https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/179
_version_ 1715723939664101376
spelling oai:cienciasmarinas.com.mx:article-1792019-04-12T00:12:08Z Lower Cretaceous Alisitos Formation at Punta San Isidro: Coastal sedimentation and volcanism Formación Alisitos del Cretácico temprano en Punta San Isidro: Sedimentación costera y vulcanismo Payne, JL Jhonson, ME Ledesma-Vázquez, J Rocky shorelines rudist limestone Alisitos Formation arc volcanism líneas de costa rocosa caliza de rudistas Formación Alisitos vulcanismo de arco The Lower Cretaceous (Aptian-Albian) Alisitos Formation is well exposed at Punta San Isidro and adjacent sea cliffs on the Pacific shores of Baja California near Eréndira, Mexico. Continuous coastal outcrops define a local stratigraphic succession less than 100 m in total thickness, including repetitious tuff, sandstone and conglomerate units interbedded with discontinuous limestone beds rarely more than 2.5 m thick. The limestone beds are biostromal units that include scattered oysters and/or corals, as well as units dominated by the rudistid bivalve, Caprinuloidea perfecta. Two distinctive conglomerate units are composed of andesite cobbles colonized by encrusting oysters in a quasi rocky-shore setting. One sandstone unit includes abundant fossil wood with tree limbs up to 55 cm long and 5 cm in diameter. Proximal volcanic activity is indicated by a series of dikes that cut through pyroclastic beds and lead to a 10-m thick andesitic flow that caps the succession at Punta San Isidro. Compared with thicker intervals of the Alisitos Formation elsewhere in Baja California that are dominated by andesitic flows and offshore limestone, the Punta San Isidro sequence offers a window on a back-reef environment adjacent to a paleoshore that received pyroclastic lahars from a terrestrial origin or mass flows from shallow submarine explosions. Recovery of marine life and the renewal of a carbonate substrate followed successive episodes of volcanism and massive erosion along an active coastline. This scenario is very different from depositional processes of the Upper Cretaceous (Campanian-Maastrichtian) Rosario Formation that cannibalized and subsequently formed a regional unconformity against tilted Alisitos strata with substantial topographic relief in the Eréndira region. La Formación Alisitos del Cretácico temprano (Aptiano-Albiano) se halla expuesta en Punta San Isidro y en los cantiles adyacentes a las costas del Pacífico de Baja California cerca de Eréndira, Mexico. Continuos afloramientos costeros definen la sucesión estratigráfica local con menos de 100 m de grosor total, incluyendo unidades repetitivas de tobas, areniscas y conglomerados intercalados con capas de calizas discontinuas raramente con más de 2.5 m de grosor. Las capas de calizas son unidades biostromales que incluyen ostiones y/o corales esparcidos, así como unidades dominadas por el bivalvo rudista Caprinuloidea perfecta. Dos singulares unidades de conglomerados están compuestas de guijas de andesita colonizadas por ostiones encrustantes en un ambiente costero semi-rocoso. Una unidad de arenisca incluye abundante madera petrificada con ramas hasta de 55 cm de largo y 5 cm de diámetro. Actividad volcánica en las cercanías está indicada por una serie de diques que cortan a través de capas piroclásticas y conducen a un flujo andesítico con 10 m de grosor, el cual sobreyace la sucesión en Punta San Isidro. En comparación con intervalos más gruesos de la Formación Alisitos en otras localidades de Baja California, que también están dominadas por flujos andesíticos y calizas marinas, la secuencia de Punta San Isidro ofrece una ventana hacia un ambiente ante-arrecifal adyacente a una paleocosta que recibió lahares piroclásticos de origen terrestre o flujos masivos provenientes de explosiones submarinas someras. La acumulación de vida marina y la renovación de un sustrato de carbonato fue la continuación a sucesivos episodios de volcanismo y erosión masiva a lo largo de una línea de costa activa. Este escenario es muy diferente a los procesos de depositación de la Formación Rosario en el Cretácico tardío (Campaniano-Maastrichtiano), la cual canibalizó y subsecuentemente formó una discordancia regional contra los estratos inclinados de la Alisitos, con sustanciales relieves topográficos en la región de Eréndira.  Iniversidad Autónoma de Baja California 2004-03-06 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Peer-reviewed Article Artículo Arbitrado application/pdf https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/179 10.7773/cm.v30i2.179 Ciencias Marinas; Vol. 30 No. 2 (2004); 365-380 Ciencias Marinas; Vol. 30 Núm. 2 (2004); 365-380 2395-9053 0185-3880 eng https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/179/154

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