Historical Review of Early Pacific Coast Micropaleontology: ABSTRACT

From its beginnings in the wake of World War I, Pacific Coast industrial micropaleontology had at its disposal the superjacent stratigraphic column blocked out by predecessors chiefly on the basis of marine megafossils. Only a few stratigraphically isolated foraminiferal faunules had been recorded in print, as by Chapman and by Bagg. With the growing interest in micropaleontology, several such local microfaunules soon were being analyzed and taxonomically described, notably by the Hanna brothers, Wissler, Church, Hughes, Hobson, Barbat and von Estorff, Galliher, Goudkoff, the Stewarts, Parker, and Siegfus. Age equivalents of the classic Tertiary time-rock subdivisions of Series-Epoch magnitude had been recognized here by Conrad, Arnold, and others. Finer time-rock subdivi ions, however, still were spoken of in terms of faunas, usually as found in mapped and formally named formations. Soon, in spite of earlier traditions to the contrary, in the minds of geologists and palentologists alike, formational terminology was being transferred into time terminology, and unhappily so, as subsequently clarified by Schenck and Muller. Other finer subdivisons, based more intrinsically upon fossils, had previously been given zonal terms. Some were simply fossil beds. J. C. Merriam's two valuable middle Tertiary Turritella zones proved, however, to be teilzones; eventually they were shown by Loel and Corey to overlap in time-stratigraphic range. Helpful echinoid bioseries proved limited in their correlative usefulness because of the lateral as well as vertical evolutionary sensitivity to selective environmental change. In turn, a fauna or an "index fossil" found at one or a few s ratigraphic zones within a formation, were apt automatically to be taken as indicative of the age of the entire formation. In short, correlations more refined in magnitude than an epoch were in essence local and particular synchroneities defying general classification, rather than biochronological deductions derived through references to some typifying standard stemming from multiple induced generalizations. Resultant confusion in semantics was reflected in the use of formational names for "stages," as reflected in the West Coast Paleogene, and the analogous use of terms such as San Lorenzo, Vaqueros, Temblor, Santa Margarita, Pancho Rico, Repetto, and Pico. For refined correlations of the sort required for the recognition of structural and stratigraphic traps in oil exploration, such sy bols were woefully inadequate. With Elliot's perfection of the core-barrel for use in rotary drilling, the significance of micropaleontology for refined correlations in oil geology was immensely enhanced. The chief vehicle involved was detailed biostratigraphy, carried on in private industrial micropaleontology after the manner of 19th century paleontologist August Quenstedt. The first published record of such a local detailed biostratigraphic continuum was that of Herschel Driver in 1928, using informal taxonomy for natural phyletic realities. In the same year, consistency along strike, of Pliocene biostratigraphic units such as Driver's, was emphasized by the late O. C. ("Jimmy") Wheeler, and soon also Neogene by Rankin, Lohman, and others. Yet biostratigraphy, left in a purely empirical state, has its chronologic hazards even over and above the factor of error that is inherent in any scientific deduction at its syllogistic best. Criticisms based on demonstrable lateral change in fauna were particularly telling; yet many geologists, by then wary, were nevertheless still thinking biochronologically in terms of William Smith's principle, which is not relevant below System-Period levels in paleontologic time-refinement. In 1933 Natland published his demonstrated parallels between five living, bathymetrically controlled, foraminiferal community-types ("ecological formations") and comparable groupings in a nearby Pliocene sequence; and though his work did not extend to either whole true communities or faunules, and biostratig aphic chronology was not attempted until later, the significance of foraminiferal chorology and facies in biostratigraphic chronology was clearly documented. Meanwhile the late Ralph Reed--active field geologist, oil company executive, and voracious reader in the field of earth history generally--had suggested that seemingly Albert Oppel, Quenstedt's student, had managed to circumvent the stumbling blocks of both ecologic and lithologic facies by culling them out of biostratigraphic data for purposes of refined biostratigraphic chronology. The suggestion was appreciated by his associates, and the germ of the consequences already appears formally in a 1931 paper by Cushman and Laiming. Subsequently 15 benthonic foraminiferal stages and more than twice as many zones, in the sense of Oppelian zonation, have been recognized within the Pacific Coast provinces of the Tertiary. End_of_Article - Last_Page 435------------