Mirror Image of Climate-Caused Foram Extinction: Pacific and Gulf Coasts: ABSTRACT

Abstract

Pacific Coast foraminiferal correlations combined with those of Lamb (1964) show that there are synchronous mirror-image biostratigraphic trends in the Oligo-Miocene of the Pacific and Gulf coasts of North America. Correlation has been established by using restricted by phylogenetically overlapping, rapidly evolving uvigerinid lineages, foraminifer End_Page 547------------------------------ zones of Bolli (1965), Bermudez (1966), Banner and Blow (1965), and radiometric dating of terrestrial mammalian remains (Evernden et al., 1964). Warm and are used to denote complex climatic events in which temperature is one of many factors influencing the biostratigraphic record. An Oligo-Miocene plankton correlation model (Rothwell, ms., Geneva, 1967) shows great mobility of benthonic lineages synchronous with poleward extension of zones of Blow et al. (1965) during warm transgressive cycles. Conversely, there are trends toward restricted mobility of both fossil plankton and benthos during major cold climatic changes at approximately 17, 24, 30, and 37 m.y.B.P. Radiometric dating within representative sequences of mammalian provincial ages and superposition of Pacific marine and nonmarine strata have established a nearly complete North American Cenozoic biostratigraphic history. No stage name has been accepted yet in Europe for an approximate 7-m.y. interval of the upper Oligocene/lower Miocene which is well represented by Pacific and Gulf Coast faunas and in the world tropical foraminifer zonation approximately in N1 to within N4 of Banner and Blow (1965). An Upper Cambrian correlation model, using the trilobite data and biomere concept of A. R. Palmer (1965), illustrates mirror-image biostratigraphic relations of benthonic and planktonic trilobites of Pacific and Atlantic sources, suggesting three major climatic cycles in the Upper Cambrian correlated with Palmer's biomere boundaries. Both the Cenozoic and Cambrian studies illustrate mirror-image biostratigraphic trends between widely separated geographic regions, suggesting major irregular synchronous climatic cycles of 3-8 m.y. duration. Uniformitarian physical (Nairn, 1965) and biologic principles can explain the analogies between the Cambrian and Oligocene-Miocene fossil occurrences which are modified by complex climatic causes resulting in unique physical and evolutionary histories. End_of_Article - Last_Page 548------------