8th International Nannoplankton Association Conference


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Ma. Antonieta Sánchez R., Patricia Padilla A., Humberto Torres, Román Landeros, Luis Lauro Villanueva, Ricardo Torres V., Janett Sánchez D.:
Biochronostratigraphic integration of an exploratory well from the southern Gulf of Mexico

The calcareous nannofossil and foraminifer content of Paleocene-Lower Pleistocene terrigenous sediments from an exploratory well, located in the southern Gulf of Mexico, were studied in great detail. The lithology and well logs of the stratigraphic column were also included.

Biostratigraphic interpretations were conducted, following the concepts of conventional biostratigraphy and the graphic correlation method. The identified nannofossil biozones of the Oligocene to the Early Pleistocene in this study include: NN19, NN18-NN15, NN11, NN5-NN1, NP25-NP-20. The planktonic foraminifera biozones are the following: Globorotalia truncatulinoides truncatulinoides, G. tosaensis tosaensis, Globorotalia miocenica, G. margaritae, G. fohsi lobata-G.fohsi fohsi(?), Catapsydrax stainforthi, C. dissimilis, Globigerinoides primordius, Globorotalia kugleri, Globigerina ciperoensis, Globorotalia opima opima, Cassigerinella chipolensis/Pseudohastigerina micra and Turborotalia cerroazulensis. The Paleocene-Eocene biozones could not be identified due to the microfossil scarcity.

Quantitative and qualitative analysis of the diversity and abundance of nannoflora and microfauna were performed. A notable increase of these parameters was observed through the Middle Pliocene-Middle Miocene, and Middle-Early Oligocene. The fossil diversity and abundance decreased considerably during Paleocene-Eocene times.

Eight terraces or discontinuities were detected with the graphic correlation method, and eight with the classical biostratigraphy method. The two methods yielded sometimes similar results, however, there are some differences that can be observed in the Early Pliocene-Middle Miocene terrace. This terrace was determined with the graphic correlation method. The nannofossil study utilising the conventional biostratigraphy indicates two important terraces: one around the Pliocene/Miocene boundary and the other one between the Late Miocene and Middle Miocene.

Most of the studied stratigraphic column was deposited in deep-water conditions, specifically in an upper bathyal setting. Only a small, external neritic interval of Early Pleistocene age was recognised.


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 [Division of Micropalaeontology] [Department of Geosciences] [Bremen University]

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