Gisela Salazar Medina, 2001. "Tertiary Zonation Based on Planktonic Foraminifera from the Marine Region of Campeche, Mexico", The Western Gulf of Mexico Basin: Tectonics,Sedimentary Basins, and Petroleum Systems, Claudio Bartolini, Richard T. Buffler, Abelardo Cantú-Chapa
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A study of foraminifera selected from the sediments of 17 wells located in the Campeche Sound, Gulf of Mexico, revealed that two wells have a column encompassing almost the complete Tertiary, whereas the remaining wells produced only samples corresponding to the Oligocene-Pleistocene.
Assessment of planktonic foraminifera allowed the establishment of a composited chronostratigraphical column for the Tertiary that encompasses the mid-Paleocene to Pleistocene. Twenty-six biozones were identified and described from oldest to youngest, 15 for the Paleogene and 11 for the Neogene.
The zonation is based on the outlines proposed by Toumarkine and Luterbacher (1985) and Bolli and Saunders (1985) for the Paleocene-Eocene and the Oligocene-Holocene, respectively. Some modifications are introduced, mainly because of the nature of the samples available for this work, as well as the local conditions of the study area.
This contribution compares the zonation described in the present study with those proposed by the authors mentioned above, as well as those of Blow (1969, 1979), Stainforth et al. (1975), and Berggren et al. (1995).
In two of the studied wells, the absence of zones at the Paleocene-Eocene boundary and at the Eocene-Oligocene boundary (Morozovella velascoensis zone at the late Paleocene and Cassigerinella chipolensis/Pseudohastigerina micra zone at the lower Oligocene) was noticed; therefore, both boundaries are unconformable. Furthermore, in all the studied wells, the Globigerinoides ruber, Globorotalia mayeri, and Globorotalia menardii zones in the upper part of the middle Miocene are missing; consequently, the middle Miocene-upper Miocene boundary is also unconformable.
Depositional environments were interpreted using the association of characteristic species of benthonic foraminifera and benthonic/planktonic ratios.
From the detailed study of one well and by applying the graphic-correlation method, a two-axis graph was generated. Four “terraces” were observed, corresponding to missing zones, which indicates that some relevant geologic events may be present in the study area, such as condensed sections, unconformity or hiatus, local structural problems (folds and faults), regional tectonic events, and diapiric intrusions.
The proposed zonation may be used as a base to carry out regional biostratigraphic correlations, as well as to provide support for future Tertiary geologic studies of the Gulf of Mexico and the Caribbean.