Larger Foraminifera and Events at the Eocene/Oligocene Boundary in the Indo-West Pacific Region
TL;DR: This article reviewed critical sequences of Late Eocene limestones in the Indo-West Pacific region to establish the nature of the faunal change at the Eocene-Oligocene boundary and linking it with any geological features of regional importance.
Abstract: Publisher Summary This chapter reviews critical sequences of Late Eocene limestones in the Indo-West Pacific region to establish the nature of the faunal change at the Eocene–Oligocene boundary and of linking it with any geological features of regional importance that may be apparent from the successions themselves. Eocene and Oligocene limestones are numerous in the Indo-West Pacific region and a great deal is known about their faunas. There is, however, little published information on the boundary itself, and only at Melinau, Sarawak, have Eocene and Oligocene limestones been found at outcrop in an apparently unbroken sequence. The major change that everywhere affected larger foraminifera at or toward the end of Eocene times seems to have been marked by a distinct depositional hiatus in most areas of shallow-water carbonate sedimentation. The cause could have been a global fall in sea level that exposed many inner shelf carbonates to erosion.
Citations
More filters
TL;DR: The evolution of planktonic foraminiferal faunas dominated by warm-water taxa, even though oxygen isotopes only recorded relatively minor cooling, can be reconciled by the explanation that the biotic communities responded to changes in trophic resources and euphotic habitats that accompanied the temperature reduction as discussed by the authors.
242 citations
TL;DR: This article reconstructed the Atlantic Ocean vertical and meridional water characteristics based on combined synoptic fossil census data, stable isotope records, and measurements of individual planktonic foraminiferal species.
Abstract: Reconstruction of Atlantic Ocean vertical and meridional water characteristics is based on combined synoptic fossil census data, stable isotope records, and measurements of individual planktonic foraminiferal species. Correlations between planktonic foraminiferal indices and specific water types and/or chemical conditions are used to trace seven stages in the history of Atlantic circulation during Eocene climatic changes: (1) warm, equable, probably saline, productive ocean of the early Eocene characterized by lowest meridional and vertical thermal gradients and the maximal extent of tropical surface water, (2) early middle Eocene expansion of subtropical waters and faunas accompanying the first climatic cooling and eutrophication of equatorial surface waters, (3) maximal partitioning of water types, faunas, and bioprovinces in middle Eocene Zone P11 accompanying maximum planktonic foraminiferal diversity, accelerated near-surface and deepwater cooling, and intensified upwelling, (4) latest middle Eocene (Zone P14) maximal planktonic foraminiferal evolutionary overturn during accelerated cooling, deep and surface water ventilation, and transformation of tropical, surface water habitat with the expansion of temperate water types and faunas; this accompanied the reduction of meridional heat transport in boundary currents, (5) late Eocene bottom water and middle-latitude cooling, broadening of meridional temperature gradients, and expanded oxygen-minimum, but faunal homogenization following the decreased import of Mediterranean water ourflow, (6) weakening and/or shoaling of the nutricline, an oxygen minimum, and the thermocline preceding a diminution of primary productivity at the Eocene-Oligocene boundary, and (7) earliest Oligocene low-productivty ocean marked by diminished vertical thermal contrasts and homogeneous foraminiferal faunas dominated by small-sized individuals. The increased areal extent of upwelling with the outcropping of cooler waters over large geographic regions provides an important climatic-forcing mechanism in the latest middle and late Eocene.
175 citations
TL;DR: The authors discusses the conflicting evidence for sea surface temperatures obtained from palaeontological and isotopic sources, and suggests that palaeotemperatures derived from some isotopic studies are too low to account for the distribution and diversity of many Tertiary tropical and subtropical biotas.
173 citations
31 Dec 1992
160 citations
135 citations
References
More filters
Journal Article•
160 citations
TL;DR: In this paper, a synthesis of available stratigraphic and foraminiferal evidence from the upper Cretaceous-Eocene sequence of various parts of the India-Pakistan-Burma region is presented.
Abstract: A synthesis of the available stratigraphic and foraminiferal evidence from the upper Cretaceous-Eocene sequence of various parts of the India-Pakistan-Burma region "shows that there were four main cycles of deposition. Each cycle is shown to have started with a transgression and ended with a regression. Evidence of minor local regression is present in some places. The earliest of these cycles ended with the Maestrichtian, and this is taken to indicate the end of the Cretaceous period. The next cycle strated with the Danian, which is now placed in the lowermost Tertiary (basal Paleocene), and continued into the Ranikot stage (Paleocene). The third and fourth cycles began with the Laki and the Khirthar stages, respectively, the two cycles together representing the whole of the Eocene."
157 citations
TL;DR: The stratigraphy of the Melinau Limestone, a pure shallow-water carbonate deposit in north-east Sarawak with a maximum thickness of about 7000 ft, is described in this article.
Abstract: The stratigraphy of the Melinau Limestone, a pure shallow-water carbonate deposit in north-east Sarawak with a maximum thickness of about 7000 ft, is described. Dating of this sequence is based almost entirely on larger Foraminifera. The changing faunal succession from Upper Eocene through the Oligocene into the Lower Miocene is described and discussed. The probable conditions of deposition are considered and a correlation between the Melinau Limestone sequence and other limestone successions elsewhere in Sarawak is proposed. The criteria usually used for dating mid-Tertiary sediments of similar type in the Tethyan region are reviewed, and an attempt is made to correlate the Melinau succession with comparable successions elsewhere in Indonesia, the Pacific, India, and the Middle East. One new genus, Wilfordia, and three new species of Foraminifera, Dictyoconus melinauensis, Neoalveolina inflata, and Wilfordia sarawakensis, are described. Dictyoconus is recorded for the first time from strata of Oligocene age.
100 citations
01 Jan 1957
TL;DR: In this article, the authors present an overview of stratigraphy in the Cretaceous system and the Miocene and Oligocene series of the Caimito formation, exclusive of Madden basin and Pacific coastal area.
Abstract: _________________________________________ _ Introduction ______________________________________ _ Historical background __________________________ _ Purpose and scope of report_ ____________________ _ Orthography of geographic names ________________ _ Acknowledgments ______________________________ _ Annotated bibliography ________________________ _ Geology __________________________________________ _ Stratigraphy __________________________________ _ Outline of stratigraphy _____________________ _ Cretaceous(?) system _______________________ _ Eocene series ______________________________ _ Gatuncillo formation ___________________ _ Eocene or Oligocene series __________________ _ Marine member of Bohio(?) formation ____ _ Oligocene series ____________________________ _ Bohio formation ______ ------__________ _ Caimito formation, exclusive of Madden basin and Pacific coastal area _________ _ Tuffaceous strata in Chorrera area _______ _ Bas Obispo formation and Las Cascadas agglomerate _________________________ _ Oligocene and Miocene series ________________ _ Caimito formation of Madden basin and Pacific coastal area ___________________ _ Miocene series _____________________________ _ Culebra formation, including Emperador limestone member ___________________ _ Cucaracha formation ___________________ _ Panama formation, including La Boca marine member and Pedro Miguel agglomerate member ___________________ _ Gatun formation _____ -------__________ _ Pliocene series _____________________________ _ Chagres sandstone, including Toro limestone member _______________________ _ Pleistocene series __________________________ _ Correlation of Tertiary forrliations in different Paa-e
83 citations
TL;DR: Drilling on Eniwetok Atoll, Marshall Islands, revealed the presence of olivine basalt beneath shallow-water limestone of Eocene age at a depth of 4,154 feet as discussed by the authors.
Abstract: Drilling on Eniwetok Atoll, Marshall Islands, revealed the presence of olivine basalt beneath shallow-water limestone of Eocene age at a depth of 4,154 feet. Two holes were put down on opposite sides of the atoll: F-1 on the northwest where a guyot (flat-topped seamount) adjoins the atoll at 700 fathoms, and E-1 on the southeast where no guyot is present. In F-1, hard basement rock was struck at 4,610 feet, but no sample recovered. In hole E-1, unweathered basalt cuttings were obtained from a depth of 4,154 feet and solid basalt core from 4,208 to 4,222 feet. Each hole penetrated several hundred feet of soft, Quaternary reef limestone before entering a thick, Tertiary section of similar rocks. The Tertiary rocks are mostly limestones with minor amounts of dolomite and dolomitic limestone. Some of the limestones are made up of clay-size and silt-size particles and are carbonaceous. Most of the section is soft or weakly consolidated. The two holes are similar to depths of 1,400 feet; below this point there are striking differences in lithologic characters, organic constitution, and the distribution of hard rock and cavities. The drilling data indicate that the atoll is a thick cap of limestone resting on the summit of a volcano that rises 2 miles above the floor of the ocean.
67 citations