Middle-late Miocene benthic Foraminifera in a western equatorial Indian Ocean depth transect; paleoceanographic implications

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doi: 10.1016/j.palaeo.2006.11.003
Author(s): Smart, Christopher W.; Thomas, Ellen; Ramsay, Anthony T. S.
Author Affiliation(s): Primary:
University of Plymouth, School of Earth, Ocean and Environmental Sciences, Plymouth, United Kingdom
Other:
Yale University, United States
Cardiff University, United Kingdom
Volume Title: Palaeogeography, Palaeoclimatology, Palaeoecology
Source: Palaeogeography, Palaeoclimatology, Palaeoecology, 247(3-4), p.402-420. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0031-0182 CODEN: PPPYAB
Note: In English. 152 refs.; illus., incl. 7 tables, sketch map
Summary: Middle through upper Miocene (17-5 Ma) benthic foraminiferal faunas (>63 µm) from a depth transect in the western equatorial Indian Ocean (DSDP Site 237, ODP Sites 707, 709 and 710; water depth 1500-3800 m) underwent significant faunal changes at ∼14-13 Ma and 11-8 Ma. These faunal changes are not easily interpreted, because of the complex factors controlling benthic foraminiferal distribution and abundance. At ∼14-13 Ma, the relative abundance of "high-productivity" taxa (Bolivina, Bulimina, Melonis and Uvigerina species), although highly variable, generally increased at the two shallower sites (237 and 707), as did the percentage of Epistominella exigua (indicative of seasonal productivity) and Nuttallides umbonifera (indicative of corrosive bottom waters) at the two deeper sites (709 and 710); the latter species had a peak in abundance at the deepest site (710) between 11 and 9 Ma. Benthic foraminiferal accumulation rates (BFARs) increased strongly at the shallower sites starting at 11 Ma, peaking between 9 and 8 Ma, and increased weakly at the deeper two sites starting at 11 Ma. Elongate, cylindrical taxa decreased in abundance between 12 and 11 Ma at all sites. The abundance of planktic foraminiferal fragments was, as expected, overall higher at the deeper sites, with some high values after 12-13 Ma at the shallower sites. The faunal changes suggest that overall the food supply to the sea floor increased, but also became more pulsed or seasonal, peaking at 9-8 Ma, while deep and intermediate waters may have become more ventilated. The first phase of faunal change (14-13 Ma) was coeval with the global increase in benthic foraminiferal oxygen isotope values, worldwide turnover in benthic foraminiferal faunas, and possibly increased production of Antarctic Bottom Water (AABW) and Northern Component Water (NCW). The overall faunal turnover may reflect the composite faunal response to increased food input resulting from heightened productivity and increased bottom water ventilation associated with a combination of monsoonal intensification, global cooling and changes in ocean circulation, but there is no unequivocal evidence for the presence of Tethyan Outflow Water (TOW) over the studied time and depth range, in contrast to earlier publications. Abstract Copyright (2007) Elsevier, B.V.
Year of Publication: 2007
Research Program: DSDP Deep Sea Drilling Project
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Antarctic Bottom Water; Benthic taxa; Bioclastic sedimentation; Bolivina; Bolivinitidae; Bulimina; Buliminacea; Cenozoic; Climate change; Cooling; Cores; Correlation coefficient; DSDP Site 237; Deep Sea Drilling Project; Epistominella; Equatorial region; Foraminifera; Indian Ocean; Invertebrata; Leg 115; Leg 24; Marine environment; Marine sediments; Melonis; Microfossils; Middle Miocene; Miocene; Monsoons; Neogene; Nutallides; ODP Site 707; ODP Site 709; ODP Site 710; Ocean Drilling Program; Paleo-oceanography; Paleocirculation; Paleoclimatology; Paleoecology; Paleoenvironment; Productivity; Protista; Rotaliina; Sedimentation; Sedimentation rates; Sediments; Statistical analysis; Tertiary; Trophic analysis; Upper Miocene; Uvigerina; Uvigerinidae; West Indian Ocean
Coordinates: S070500 S070459 E0580729 E0580728
S073244 S073243 E0590101 E0590100
S035454 S035454 E0603306 E0603306
S041842 S041842 E0605848 E0605848
Record ID: 2007053129
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands