Foraminiferal distribution off the southern tip of India to understand its response to cross basin water exchange and to reconstruct seasonal monsoon intensity during the Late Quaternary Thesis submitted to the Goa University School of Earth, Ocean, and Atmospheric Sciences for the award of degree of Doctor of Philosophy by Dharmendra Pratap Singh Goa University School of Earth, Ocean, and Atmospheric Sciences, Goa University (Micropaleontology Laboratory, Geological Oceanography Division CSIR- National Institute of Oceanography, Dona Paula, Goa) April 2019 i Declaration As required under the university ordinance OA.19, I hereby state that the present thesis entitled “Foraminiferal distribution off the southern tip of India to understand its response to cross basin water exchange and to reconstruct seasonal monsoon intensity during the Late Quaternary” is my original contribution and the same has not been submitted on any pervious occasion. To the best of my knowledge, the present study is the first comprehensive work of its kind from the area mentioned. Literature related to the scientific objectives has been cited. Due acknowledgments have been made wherever facilities and suggestions have been availed of. Dharmendra Pratap Singh ii Certificate As required under the university ordinance OA.19, I certify that the thesis entitled “Foraminiferal distribution off the southern tip of India to understand its response to cross basin water exchange and to reconstruct seasonal monsoon intensity during the Late Quaternary” submitted by Mr. Dharmendra Pratap Singh for the award of the degree of Doctor of Philosophy in the School of Earth, Ocean, and Atmospheric Sciences is based on original work carried out by him under my supervision. The thesis, partially or completely, has not been previously submitted for any other degree or diploma in any university or institution. (Rajeev Saraswat) Supervisor iii Preface The northern tropical Indian Ocean and adjoining landmass are influenced by seasonal reversal of monsoon wind that has a profound impact on the socio-economic conditions of one of the most densely populated regions of the world. Monsoon in this region comprises of two distinct phases (summer and winter monsoon) with over 80% of the average precipitation in Indian subcontinent during summer monsoon. The north-eastern and south-eastern Indian states as well as Andaman-Nicobar region, receives substantial rainfall during winter monsoon. Two-phases of monsoon are the result of seasonally reversing winds and migration of intertropical convergence zone (ITCZ). The seasonally reversing winds and associated physical forces cause strong upwelling in the open ocean, off Somalia, Oman and the region off the southern tip of India. The seasonally reversing winds also generate coastal currents. The coastal currents transport warm saltier water from the Arabian Sea into Bay of Bengal during summer and cold relatively less saline water back from the Bay of Bengal into the Arabian Sea during the winter season. The cross basin exchange of water takes place through the region off southern tip of India. The seasonally reversing winds and currents cause significant physico-chemical changes in the region off south India. The fauna living in the region off the southern tip of India are affected by these seasonally changing physico-chemical conditions, especially by the seasonal phytodetritus pulse and high nutrient supply that affects both planktic and benthic fauna. This region also preserves the record of temporal changes in seasonally reversing conditions. The aim of my Ph.D. was to understand the effect of these seasonal changes on foraminifera and to reconstruct seasonal climatic conditions from this region. The work has been compiled in eight chapters. The summary of each chapter is given below. Chapter one comprises rational of the work including the general introduction of the scientific problem. This is followed by the detailed literature review from the region off the southern tip of India as well as adjacent regions. The detailed literature review helped to find out the knowledge gap. Limited information is available about the distribution of living benthic foraminifera and the factors affecting it, from the region off the southern tip of India. The paleoclimatic reconstruction is also limited to a few records iv covering only a part of the Holocene. Based on the available information, the following objectives were set for the doctoral work. 1. To document modern foraminiferal distribution from the region off the southern tip of India. 2. To understand the effect of seasonal physico-chemical changes on the foraminiferal distribution to develop proxies to infer seasonal monsoon changes. 3. To reconstruct changes in relative strength of summer and winter monsoon intensity during the Late Quaternary. 4. To reconstruct changes in the Indo-Pacific warm pool during the Late Quaternary. Chapter two provides details of the selected study area, i.e. the region off the southern tip of India. It also includes modern physico-chemical conditions during summer/winter monsoon as well as its annual variability. The details of sea surface temperature (SST), salinity, dissolved oxygen, primary productivity; rain fall, wind pattern and related changes in atmospheric and oceanic circulation in the region off the southern tip of India are included in this chapter. The chapter also provides a glimpse of the modern spatial structure of the Indo-Pacific Warm Pool. Chapter three includes details of the sediment samples and the analysis done to fulfill the objectives. A total 1219 samples (43 surface samples and 1176 subsurface samples) were used. The samples were collected during the 4th cruise of RV Sindhu Sadhana (SSD004) in October 2014, after the end of the summer monsoon. The surface samples were collected along the four transects by using a multi-corer. The multi-corer sediments were subsampled at 1 cm interval. The top two sections (0-1 and 1-2 cm sediment samples) were stained with rose-Bengal ethanol solution to identify the living benthic foraminifera. The samples were processed by following the standard freeze drying method and wet sieved by using a 63 µm sieve. The living benthic foraminifera were picked from the processed coarse fraction. All picked specimens were identified up to species level. The generic level identification was done by following the treatise (Leoblich and Tappan, 1988) and the species level identification was done by using previous publications and confirmed with Ellis and Messina catalogue of foraminifera (2007). Foraminifer’s images were captured by using Scanning Electron Microscope HITACHI TM3000 version .02-02. The foraminiferal micrographs were arranged in v plates by using Adobe Photoshop (Version 10.0.3). The statistical analysis was also performed to explore the relationship between ecological parameters and faunal abundance by using Plymouth Routines In Multivariate Ecological Research (PRIMER), MultiVariate Statistical Package (MVSP) and Statistica-8 software. The sub-surface samples were collected by using a gravity corer. Two gravity cores (SSD004 GC03 and SSD004 GC11) were used to reconstruct past hydrographic changes in the region. The core SSD004 GC03 (557 samples) was collected from 7.2254°N and 77.9458°E (water depth 1540 m). The chronology of core SSD004 GC03 was established from 9 accelerator mass spectrometer (AMS) radiocarbon (14C) dates. The core covers the last 38 kyr and the sedimentation rate varies from 3.6 to 41.3 cm/kyr with an average of 18.0 cm/kyr. The average sample resolution was ~68 years. The second core SSD004 GC11 (584 samples) was collected from 6.0000°N and 78.9312°E (water depth 2901 m). The chronology of the upper section of the core was established from 3 AMS 14C dates. The older section of the core was dated by comparing the stable oxygen isotopic ratio of surface dwelling planktic foraminifera with global isostack (LR04 Benthic Isostack) (Lisiecki and Raymo, 2005). The core SSD004 GC11 covers the last 176 kyr with an average sedimentation rate of 4 cm/kyr. The coarse fraction of core samples was dry sieved and ≥150 µm fraction was used to pick planktic foraminifera. Globigerinoides ruber picked from 250-350 µm fraction were used to measure isotopic (δ18O and δ13C) and trace elements (Mg/Ca and Ba/Ca) ratio. The stable isotopic ratio was measured by using Thermo Fisher Scientific 253 plus gas isotope ratio mass spectrometer with Kiel IV automated carbonate preparation device. The trace element composition of foraminiferal tests was measured by using Agilent Technologies 700 Series Inductively Coupled Plasma-Optical Emission Spectrometer equipped with an auto-sampler (ASX-520), at MARUM, University of Bremen, Germany. The total, inorganic and organic carbon as well as nitrogen in core samples was measured to reconstruct past productivity conditions. A small amount (~5 gm) of sediment from unstained half was freeze-dried and powdered by using a clean agate mortar pestle. The total inorganic carbon (TIC) in the sediment was analyzed by using coulometer (model CM 5015 CO2), and the total carbon as well as nitrogen was analyzed by using elemental analyzer (Thermo Scientific model FLASH 2000). The organic carbon (%Corg) was calculated by subtracting TIC from total carbon. vi The detailed taxonomy and photographic illustration of all identified foraminifera species is included in Chapter four. A total 355 species of foraminifera were identified. Out of 355 species, 330 belong to benthic