Oxygen and carbon stable isotope studies onGloborotalia menardii from Pleistocene DSDP Cores in northern Indian Ocean and their paleoclimatic and paleoceanographic implications (original) (raw)
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Paleoceanography, 1995
Numerous studies have shown that delta18O records from benthic and planktonic foraminifera, primarily a proxy of global ice volume variations, reflect Milankovitch periodicities. To study climatic response to orbital forcing at Ocean Drilling Program site 758, we have generated continuous delta18O and delta13C records from a single benthic foraminiferal species Cibicides wuellerstorfi for the last 3.6 m.y. and extended the planktonic foraminiferal isotope records of Farrell and Janecek (1991) (0-2.5 Ma, based on Globigerinoides sacculifer) to 3.6 Ma (Chen, 1994). We then constructed an age model by matching, correlating and tuning the benthic delta18O record to a model simulation of ice volume (Imbrie and Imbrie, 1980). The filtered 41- and 23-kyr signals based on the resultant astronomically tuned age model are highly correlated to obliquity (r=0.83) and precession (r=0.75), respectively. Although derived with methodology different from Shackleton et al. (1990) and Hilgen (1991a,b)...
Journal of Asian Earth Sciences, 2006
This study attempts to analyse paleoceanographic changes in the Central Indian Ocean (Deep Sea Drilling Project Site 237), linked to monsoon variability as well as deep-sea circulation during the Plio-Pleistocene. We used factor and cluster analyses of census data of the 34 most dominant species of benthic foraminifera that enabled us to identify five biofacies: Astrononion umbilicatulum-Uvigerina proboscidea (Au-Up), Pullenia bulloides-Bulimina striata (Pb-Bs), Globocassidulina tumida-Nuttallides umbonifera (Gt-Nu), Gyroidinoides nitidula-Cibicides wuellerstorfi (Gn-Cw) and Cassidulina carinata-Cassidulina laevigata (Cc-Cl) biofacies. Knowledge of the environmental preferences of modern deep-sea benthic foraminifera helped to interpret the results of factor and cluster analyses in combination with oxygen and carbon isotope values. The biofacies indicative of high surface productivity, resulting from a stronger South Equatorial Current (Au-Up and Pb-Bs biofacies), dominate the early Pliocene interval (5.6-4.5 Ma) of global warmth. An intense Indo-Pacific 'biogenic bloom' and strong Oxygen Minimum Zone extended to intermediate depths (w1000-2000 m) over large parts of the Indian Ocean in the early Pliocene. Since 4.5 Ma, the food supply in the Central Indian Ocean dropped and fluctuated while deep waters were corrosive (biofacies Gt-Nu, Gn-Cw). The Pleistocene interval is characterized by an intermediate flux of organic matter (Cc-Cl biofacies). q
Palaeogeography, Palaeoclimatology, Palaeoecology, 1999
Palaeoceanographic conditions in the eastern Indian Ocean for the last ∼30 kyr are documented by means of planktonic foraminiferal analyses of 10 gravity cores. Quantitative foraminiferal analysis (%), Q-mode factor analysis, the modern analog technique (MAT) and oxygen-isotope analyses are used. A conspicuous increase during the last glacial maximum (LGM) of foraminiferal fragmentation resulting from a more productive Java upwelling system and/or a more corrosive Antarctic Intermediate Water (AAIW) was found at intermediate water depths (∼1000 m). Contrasting Q-mode factors based on foraminifera between today and the LGM suggest changes in the thermocline depth, sea-surface temperature (SST), upwelling, and the strength of both the Australasian Mediterranean Water (AAMW) and the Indian Central Water (ICW). The decrease in the percentage abundance of shallow-dwelling and symbiont-bearing planktonic foraminifera, the increase in percentage of the upwelling-related species Globorotalia cultrata and Neogloboquadrina dutertrei, and factor 3 (dominated by Globorotalia tumida and Globigerinella siphonifera) suggest a stronger Java upwelling system during the LGM. A steeper, steric latitudinal gradient (in the presence of a weak Leeuwin Current), and a geostrophic flow similar to today's is postulated for the LGM, and this must have prevented upwelling offshore Western Australia. Today's AAMW–ICW sharp front was weaker during the LGM when the AAMW was saltier, cooler, and nutrient richer and more similar to the ICW. During the LGM, a more gentle SST latitudinal gradient over the ∼16 to ∼23°S region contrasts with today's steeper conditions at the AAMW–ICW Front. Also, for the LGM, a nutrient-rich ICW may explain previously documented increases in mass accumulation rates of CaCO3, organic carbon and benthonic foraminifera in a region where the nutricline was deep and within the lower euphotic zone.
Journal of Asian Earth Sciences, 2019
Here we present the first detailed planktonic and benthic 13 C records and benthic foraminiferal assemblage records from the northeastern Indian Ocean to decipher the palaeoceanographic changes during the last 56 kyr. We identified three different palaeoceanographic stages, clearly differentiated by significant variations in the benthic foraminiferal assemblages and 13 C records. The results of this study indicate that productivity was generally higher during the glacial periods than during the Holocene. Comparison of the benthic foraminiferal assemblage distributions and planktonic and benthic 13 C records show a significant correlation between productivity and the bottom water oxygenation on glacial-interglacial timescales. Productivity gradually increased during the period between 56-27.5 kyr. During this period, the dominance of Melonis spp. and Oridosalis umbonatus were correlated with conditions of intermediate to high surface productivity and moderate bottom water oxygenation. Increased higher equatorial productivity and low bottom water oxygenation during the period between 27.5-15 kyr are supported by planktonic 13 C and faunal records. During this period, the dominance of benthic foraminifera assemblages characterised by Uvigerina peregrina indicates sustained continuous phytodetritus flux to the seafloor from enhanced surface water productivity and relatively low bottom water oxygenation. The absence or minimal occurrences of high productivity indicating U. peregrina, the dominance of intermediate to low productivity indicating fauna, and relatively low planktonic 13 C records suggest low productivity and active deep-water oxygenation after 15 kyr. Concurrent river discharge and rising sea levels during this period are indicated by negative 18 O of G. ruber at the site.
Ocean Science Journal, 2009
Oxygen isotopic analysis of planktic foraminifera (Globigerina bulloides) from a total of 23 surface sediment samples collected along a north-south transect (9.69°N to 55.01°S) in the southwestern Indian Ocean during the Indian Pilot Expedition to Southern Ocean (PESO), was carried out to assess the relationship between oxygen isotopic composition and ambient seawater temperature and salinity. An increasing trend in the δ 18 O value is noticed towards higher latitude. Apparently such an increase in δ 18 O values is inversely related to the seawater temperature changes along the transect. However, slight mismatch is observed at a few stations, which is attributed to significant seawater salinity changes. The preliminary results of the present study, if extended to the subsurface sediments coupled with other parameters, may contribute to the reconstruction of the paleohydrography of the region, especially the position of various seawater fronts during the geologic past, albeit with areal limitation.
Glacial to Holocene changes in the surface and deep waters of the northeast Indian Ocean
Marine Geology, 2012
Stable carbon and oxygen isotopic investigations are carried out on planktonic and benthic foraminifera from an AMS-dated sediment core of the northeast Indian Ocean (NEIO) to infer glacial to Holocene changes in surface and deep waters. The chronology of this gravity core (SK157-14; water-depth 3306 m; lat. 5°11'N; long. 90°05'E) was established using six AMS radiocarbon ages and oxygen isotope stratigraphy. Variations in δ18O and δ13C values of planktonic (Globigerinoides ruber) and benthic foraminifera (Cibicidoides spp.) are suggestive of large changes in the surface and deep water characteristics during the last ~ 60 ka. The δ18Opl values in core SK157-14 are significantly higher compared to the sediment cores in the northern Bay of Bengal and the Andaman Sea because of the diminished influence of riverine fresh water fluxes. Large variations in planktonic δ18Opl are noticed during the Marine Isotopic Stage (MIS) 3.1 and 3.3. Glacial to Holocene Δδ18Opl amplitude (1.8‰) is consistent with other published oxygen isotope records from the nearby locations. Maximum enrichment in δ18Opl occurs at 24-19 and the minimum during 7-6 ka BP. Spectral analysis of planktonic δ18Opl time series suggests a teleconnection between surface water δ18O and North Atlantic climate oscillations. Benthic foraminiferal δ18Oben values indicate deep water cooling of ~ 1.5 °C during the last glacial maximum. The δ13Cben values are generally higher for the Holocene foraminifera suggesting greater contribution from the North Atlantic Deep Water (NADW). However glacial benthic foraminifera are characterized by lower δ13Cben values. Highly depleted δ13Cben values during the ~ 60-50, 21-17 and 13-11 ka BP intervals suggest decrease contribution from the North Atlantic Deep Water (NADW) and increase influx from the Southern Ocean Deep Water (SODW). In addition, oxidation of organic matter and ageing of the deep water may have contributed in the pronounced decrease in δ13Cben during the glacial intervals.
1990
Combined data on benthic foraminifers, siliceous fossils, and stable isotopes depict times of enhanced organic carbon oxidation in the sediments and high primary productivity in the southern Indian upwelling zone during the Miocene. Increased abundance of the diatom productivity index, the Thalassionema group, elevated diatom and uvigerinid abundances, and bolivinid diversity all suggest heightened primary productivity and the development of a mid-depth oxygen minimum between ~17 and 10 Ma.The abundance of bolivinids with large pores and crenulate chamber surfaces may indicate more aerated pore waters in the upper few centimeters of the partly siliceous sediments deposited during the episode of higher primary productivity and increased organic carbon flux around 10 Ma.
Journal of Foraminiferal Research, 2022
The Indonesian Throughflow region connects the tropical Pacific Ocean with the eastern Indian Ocean, and variability of the Throughflow during the Plio-Pleistocene has been related to major climate shifts at the global level. Planktic foraminiferal biostratigraphy integrated with magnetochronology provides a robust time framework for assigning age control to major paleoceanographic events. Understanding of the coupled histories of the El Niño Southern Oscillation, Western Pacific Warm Pool, Indonesian Throughflow, and the eastern Indian Ocean has greatly benefitted from the chronological framework provided by planktic foraminiferal biostratigraphies from these regions. Ocean Drilling Program (ODP) Hole 762 lies under the influence of the Leeuwin Current, originating from the Indonesian Throughflow. Multiproxy data have been collected from Hole 762B and other nearby sites for paleoceanographic interpretation. However, a detailed planktic foraminiferal biostratigraphy integrated with magnetochronology is not available from this site. We provide here the sequential order of planktic foraminiferal First Occurrence (FO) and Last Occurrence (LO) events, which allowed us to divide the examined section into seven biostratigraphic zones. The biostratigraphy was integrated with magnetostratigraphy using revised ages of magnetochrons, which yielded biochronological age estimates for planktic foraminiferal events. A major planktonic faunal turnover between 3.4 and 2.7 Ma is probably related to the onset of the Northern Hemisphere glaciation and related changes in the Indonesian Throughflow. We have compared our numerical age estimates with published ages from other parts of the world. The diachronism observed probably is related to the local oceanographic setting of ODP Hole 762B, which has been alternatively influenced by changing strengths of the warm Leeuwin Current and the cold west Australian Current. The biochronology established here will be useful for correlating paleoceanographic events in the region.