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| Format: | Artículo científico |
| Language: | en |
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Universidad Nacional Autónoma de México
2000
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| Online Access: | https://www.redalyc.org/articulo.oa?id=57217101 |
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Table of Contents:
- First Paleogene selachifauna of the middle American-Caribbean Antillean region, La Mesa de Copoya, west-central Chiapas, Mexico Geologic setting Shelton P. Applegate Luis Espinosa Arrubarrena Ismael Ferrusquía Villafranca Ciencias de la Tierra The area lies between 16º35-16º45 N Lat. and 93º00-93º10 W Long; and consists of 323.3 km2 ofmoderately rugged terrain set between 380-1,240 mamsl, formed by these units: Sierra Madre Limestone(Middle Cretaceous, light olive gray, thick bedded biomicrite, 800 m thick occurring in the southwest),Angostura Formation (Late Cretaceous, light gray, medium bedded, sparsely fossiliferous biomicrite tobiomicrudite and calcarenite, 300-350 m. thick, cropping out both in the southwest and northeast), SoyalóFormation (Paleocene, gray, shaly, thin bedded, arkosic-phyllarenitic, clayey siltstone, 150 m. thick; it isexposed in the outer margins of the lowlands that surround La Mesa de Copoya, which is the outstandingphysiographic feature of the area), El Bosque Formation (Early Eocene, grayish red, medium to thick bedded,phyllarenitic sandstone and breccioid conglomerate, 100 m. thick, occurring out in the southern lowlands.),and San Juan Formation (Middle Eocene, marly -quartz phyllarenitic- biomicrite to biosparrudite withbiostromic zones, intercalated with biomicrudite-supported, coarse grained sand-granule-to-gravel, quartzphyllarenitic sandstone to conglomerate; the unit becomes less limy upward (upper third), is 450 500 m.thick, makes up both La Mesa and the slope around it, and bears the name-sake selachifauna. Quaternarydeposits complete the sequence.The Pre-Quaternary units are broadly folded into a NW-SE trending syncline, disrupted by faults. Thearea largely records Cretaceous-Paleogene marine sedimentation -punctuated by Early Eocene continentaldeposition- that ceased sometime during the Tertiary, probably by Late Miocene time, because of a changein the tectonic regime that led to folding, fracturing/faulting and regional uplift. Subsequent erosion nearlyremoved the Tertiary units, the remainder is preserved in the syncline nucleus. 2000 artículo científico 1026-8774 https://www.redalyc.org/articulo.oa?id=57217101 en http://www.redalyc.org/revista.oa?id=572 Revista Mexicana de Ciencias Geológicas application/pdf Universidad Nacional Autónoma de México Revista Mexicana de Ciencias Geológicas (México) Num.1 Vol.17