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The AAPG/Datapages Combined Publications Database

GCAGS Transactions


Gulf Coast Association of Geological Societies Transactions
Vol. 19 (1969), Pages 555-558

Coiling Directions in Planktonic Foraminifera from the Coastal Group of Jamaica

E. Robinson


Dominant coiling directions were noted in the G. menardii, G. acostaensis/G. dutertrei and G. crassaformis/G. truncatulinoides groups in the Middle Miocene to Pleistocene Coastal Group of Jamaica. Several reversals of coiling direction in the G. menardii lineage occur at the top of the Miocene (Buff Bay Formation) before dextral coiling dominates Pliocene assemblages. A period of dextral coiling in the G. crassaformis group is seen in the Pliocene (lower part of the Bowden Formation), coinciding with increasingly abundant G. miocenica and G. fistulosus. Globoquadrina altispira disappears from the sequence just before reversal to sinistral coiling in G. crassaformis. Sinistrally coiled G. menardii reappears in the impoverished planktonic faunas at the top of the Bowden Formation. The direction of coiling in the G. tosaensis/G. truncatulinoides group is variable near the base of the Manchioneal Formation, but becomes dextral with the near-disappearance of G. tosaensis. At least some of the coiling changes appear to have regional correlative value in the Caribbean and Gulf of Mexico.

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