Impact of productivity events on the benthic foraminiferal fauna in the Arabian Sea over the last 150,000 years

Abstract

We have studied the sediment geochemistry and benthic foraminiferal fauna in a piston core from the northwest Arabian Sea (covering the last 150,000 years), and compared the results with the stable isotopic record from both benthic (Uvigerina peregrina) and planktonic (Globigerinoides sacculifer) foraminifera. The δ18O record of the planktonic foraminiferal species shows excursions towards heavier δ18O values when compared to the benthic record and the SPECMAP stack, particularly in stage 3, between approximately 30 and 45–50 kyr. We call this the “stage 3 event.” Species diversity and relative abundance data on benthic foraminifera reveal that some species, e.g. Cibicidoides wuellerstorfi, Oridorsalis umbonatus, Pullenia bulloides, Pyrgo spp., and the uvigerinids increased in relative abundance during glacial stages 2 and 4 and during the stage 3 event, whereas other (e.g., Astrononion novozealandicum, Cibicidoides bradyi, Eggerella bradyi, Gyroidina altiformis, Hoeglundina elegans, Pullenia subcarinata, and Sigmoilina edwardsii) decreased. Using correspondence analysis we determined that approximately 50% of the total sample variation may be accounted for by three first factors which all are interpreted as primarily related to surface water productivity and the quality of the organic matter that reaches the seafloor. The relative abundance of some species appears to vary on a precessional cycle, perhaps responding to monsoon‐driven upwelling and associated increased food supply, whilst the abundances of other species are related to the 100 kyr ice volume cycle, and may be responding to changes in intermediate and deep water chemistry. Geochemical paleoproductivity tracers, such as the Ba content of the sediment, have a very similar distribution to specific foraminiferal factors in both time and frequency domains. Certain planktonic foraminifera, (e.g., Globigerina bulloides), also display obvious maxima in the stage 3 event. The stage 3 event occurs at a time of reduced rate of amplitude change in both solar radiation and monsoon pressure index. We conclude, that there was a period 15 to 20 kyr duration during stage 3 with cooler‐than‐normal surface waters, enhanced productivity and rapid settling of biogenic matter.

A multi-proxy analysis of late Quaternary Indian monsoon dynamics for the Maldives, Inner Sea

“…The dependence of oxygen changes in Indian Ocean water masses from the inflow of Atlantic and Antarctic water masses is corroborated by a number of recent observations from the northwestern and southeastern Arabian Sea (Pattan and Pearce, 2009;Naik et al, 2017). We therefore assume that the OMZ variability in the Maldives Inner Sea is The long period of lowered [O 2 ] values below 60 µmol kg -1 centred at MIS 4-3 coincides with a marked monsoon and upwelling maximum in the Arabian Sea (Hermelin and Shimmield, 1995;Clemens and Prell, 2003;Leuschner and Sirocko, 2003;Caley et al, 2011a, b), which caused a strengthening and deepening of the OMZ (Almogi-Labin et al, 2000;Den Dulk et al, 2000;. The expansion of the Arabian Sea OMZ southward into the equatorial region likely preconditioned the oxygen levels of intermediate waters of the Maldives Inner Sea.…”

A multi-proxy analysis of Late Quaternary ocean and climate variability for the Maldives, Inner Sea

“…All samples were wet-sieved over a 63 µm screen and the residues were subsequently dried at 38 • C. The benthic foraminiferal analysis was carried out on the > 125 µm size fraction and based on allocate splits in order to obtain approximately 300 tests. Genus and species identifications were mainly based on Loeblich and Tappan (1988), Hottinger et al (1993), Jones (1994), Debenay (2012), Milker and Schmiedl (2012) and Holbourn et al (2013). The genera Cymbaloporetta and Tretomphaloides were summarized as meroplanktonic benthic foraminifera (BF) since they are known to have planktonic drift phases as part of their dispersal strategy (Banner et al, 1985;Alve, 1999).…”

Benthic Foraminiferal Response to the Millennial-Scale Variations in Monsoon-Driven Productivity and Deep-Water Oxygenation in the Western Bay of Bengal During the Last 45 ka

“…The benthic foraminiferal distribution in deep sea is primarily controlled by primary productivity-related organic matter flux to the sea floor and dissolved oxygen level (Otto et al, 1995;den Dulk et al, 1998den Dulk et al, , 2000von Rad et al, 1999;Schmiedl and Leuschner, 2005;Bharti and Singh, 2013;Singh et al, 2015). In this study, we evaluate the benthic foraminiferal response to the past changes in surface productivity in western BoB.…”

“…Benthic foraminifera strongly responds to the variation in benthic environment by showing variations in their abundances, diversity, microhabitats, and adaptive morphologies (e.g., Corliss, 1985;Corliss and Chen, 1988;Corliss and Emerson, 1990;Corliss and Fois, 1990;Kaiho, 1994;Almogi-Labin et al, 1996;Gupta and Thomas, 1999;Nigam et al, 2007;Singh et al, 2015;Verma et al, 2018;Ma et al, 2019). Therefore, temporal variations in benthic foraminiferal assemblage in terms of these faunal parameters are extensively used to reconstruct past deep-sea environments (e.g., Corliss, 1986;Schnitker, 1994;Otto et al, 1995;Thomas and Gooday, 1996;Schmiedl et al, 1998;Drinia et al, 2004;Ma et al, 2019).…”

“…Arabian Sea (AS) and Bay of Bengal (BoB) are the two basins in the northern Indian Ocean with different oceanographic features. The fossil records of deep-sea benthic foraminiferal assemblages in the AS have been extensively used to reconstruct the history of past changes in the deep-water environment (primarily oxygen and trophic conditions) and to understand its linkage with monsoon and deep-water circulation (Hermelin and Shimmield, 1990;Otto et al, 1995;den Dulk et al, 1998den Dulk et al, , 2000Schmiedl et al, 1998;Gupta and Thomas, 1999;von Rad et al, 1999;Schmiedl and Leuschner, 2005;Arumugm et al, 2014;Sarkar and Gupta, 2014). Results of earlier studies provided deep insight into the surface ocean circulation, deep-water ventilation through externally sourced water masses impacting development of oxygen minimum zone (OMZ) and benthic environment in AS and its atmosphere-ocean teleconnections with climatic fluctuations at different timescales.…”