Benthic foraminifers from the Concepcion and Encanto strata of southeastern Mexico, Isthmus of Tehuantepec, are identified and illustrated (by scanning electron and light photomicrographs). The ranges of key planktic foraminifers and calcareous nannoplankton indicate that the Concepcion and Encanto strata of the study area range from Neogene Zones 19 and 20 Blow (1969) and are lower Pliocene in age The study is based on eighty-two samples from 38 localities within a 600 sq. km. area that is centered around the town of Acayucan, Veracruz, in the western Salina Basin. A total of 214 species and subspecies of benthic foraminifers are identified and described from the Encanto and Concepcion strata. These deposits, traditionally subdivided into upper and lower Concepcion Formations and Encanto Formation by Mexican geologists, are not formations but biostratigraphic units Three assemblage zones, based on key benthic foraminifers, are proposed to define these units. The Encanto strata, with a middle to upper bathyal paleobathymetry, is represented by the Melonis affinis - Uvigerina hispida Assemblage Zone. This unit is overlain by the lower Concepcion beds represented by the Marginulinopsis hispaniolanus - Anomalinoides nucleatus Assemblage Zone (upper bathyal to outer neritic). The youngest unit, the upper Concepcion deposit, is defined by the Bolivina imporcata - Saracenaria nuttalli Assemblage Zone (outer neritic to middle neritic) / acase@tulane.edu
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_24410 |
| Date | January 1980 |
| Contributors | Kohl, Barry (Author) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Rights | Access requires a license to the Dissertations and Theses (ProQuest) database., Copyright is in accordance with U.S. Copyright law |
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