Miocene Indian Ocean circulation; a high-resolution multivariate analysis of interbasinal records

Author(s): Irving, D. H.; Smart, C.; Ramsay, A. T.; Thomas, E.
Author Affiliation(s): Primary:
University of Manchester, School of Earth, Atmospheric and Environmental Sciences, Manchester, United Kingdom
Other:
University of Plymouth, United Kingdom
Cardiff University, United Kingdom
Yale University, United States
Volume Title: AGU 2006 fall meeting
Source: Eos, Transactions, American Geophysical Union, 87( Fall Meeting Suppl.); American Geophysical Union 2006 fall meeting, San Francisco, CA, Dec. 11-15, 2006. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0096-3941 CODEN: EOSTAJ
Note: In English
Summary: Ocean circulation in the Indian Ocean during the Miocene progresses through three configurations in response to changes in plate movement and global climate. Principal Component Analysis (PCA) was carried out on benthic foraminifera, stable isotope and sedimentological data sampled at 100 kyr intervals from cores recovered from ODP sites 237, 707, 709 and 710 in the Somali Basin (SOB) and sites 214, 216 and 238 in the Mid-Indian Basin (MIB). These analyses provide insight into the structure and dynamics of the Indian Ocean through most of the Miocene (25--6 Ma) and suggest forcing mechanisms of the circulation system in this and adjacent ocean basins. Bulk responses of infaunal and epifaunal species mask local and regional oceanic signals that this study extracts by analysis at the species level. Isotopic ratios are used to describe the depth structure of the two basins. Coupled with sedimentological data, the dynamics of the basins is described in terms of the major events of the Miocene, namely Tethyan closure, the growth of the West Antarctic Ice Sheet (WAIS) and the initiation of the monsoon. PCA of the time series data show three separate components which correlate with these three phases in the history of the Indian Ocean. These are: i) 25-18 Ma, a stratified SOB with warm dense Tethyan outflow waters (TOW) underlying cooler, less dense water that is weakly coupled across the Chagos- Laccadive Ridge (CLR) with an unstratified MIB; ii) 18-12 Ma, mixing in the SOB as TOW diminishes due to seaway closure, and increasing cool bottom waters which penetrate further north with time, accompanied by stratification of the MIB and stronger coupling of surface waters promoting nutrient transfer eastwards; iii) 12-6 Ma, overturn and upwelling in the SOB with occasional strong fluxes of cooler WAIS bottom water and strong stratification in the MIB, with a westerly flux of warm water overtopping a more greatly subsided CLR.
Year of Publication: 2006
Research Program: DSDP Deep Sea Drilling Project
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Antarctic ice sheet; Antarctica; Basins; Benthic taxa; Cenozoic; Chagos-Laccadive Ridge; Cores; DSDP Site 214; DSDP Site 216; DSDP Site 237; DSDP Site 238; Deep Sea Drilling Project; Foraminifera; Glacial geology; High-resolution methods; Ice sheets; Indian Ocean; Invertebrata; Isotopes; Leg 115; Leg 22; Leg 24; Marine sediments; Microfossils; Mid-Indian Basin; Miocene; Multivariate analysis; Neogene; ODP Site 707; ODP Site 709; ODP Site 710; Ocean Drilling Program; Paleo-oceanography; Paleocirculation; Principal components analysis; Protista; Sediments; Somali Basin; Stable isotopes; Statistical analysis; Stratification; Tertiary; Time series analysis; Upwelling; West Antarctic ice sheet
Coordinates: S110913 S110912 E0703134 E0703133
S112013 S112013 E0884305 E0884305
N012743 N012744 E0901229 E0901228
S070500 S070459 E0580729 E0580728
S073244 S073243 E0590101 E0590100
S035454 S035454 E0603306 E0603306
S041842 S041842 E0605848 E0605848
Record ID: 2007080018
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