Indian Ocean high-productivity event (10–8 Ma): Linked to global cooling or to the initiation of the Indian monsoons?

Abstract

Uplift of the Himalayas and Tibetan Plateau (ca. 10-8 Ma) has been said to be the main cause of the origin or intensification of the Indian monsoon system, because mountains modulate the land-sea thermal contrast. The intensification of the monsoons, in turn, is seen as the cause of major changes in fauna and flora on land (as a result of changing precipitation patterns) as well as in the Indian Ocean, where the monsoons drive increased upwelling and thus increased productivity. We argue that the interactions between the elevation of the Himalayas and Tibetan Plateau, the onset of the monsoons, and their effects on the Indian Ocean biota remain uncertain. The timing of these events (uplift, monsoons, and biotic change) is not well constrained. Neogene deep-sea benthic foraminiferal faunal and isotope records of the Ninetyeast Ridge combined with published data show that a major increase in biogenic productivity occurred at 10-8 Ma throughout the Indian Ocean, the equatorial Pacific, and southern Atlantic. We suggest that this Indian Ocean high-productivity event was not simply the result of monsoon-induced upwelling or nutrient delivery from the weathering of newly uplifted mountains, but may have been caused by strengthened wind regimes resulting from global cooling and the increase in volume of the Antarctic ice sheets.

Endolithic Boring Enhance the Deep-sea Carbonate Lithification on the Southwest Indian Ridge

“…1). It has been well proved that thriving biogenic bloom through the Indian Ocean were bursting 30 during the Latest Miocene-Early Pliocene by ODP sediment sequences (Arumugm et al, 2014;Gupta et al, 2004;Rai and Singh, 2001;Singh et al, 2012). The bloom lead to significantly higher carbonate mass accumulation rates than present day Biogeosciences Discuss., https://doi.org /10.5194/bg-2018-46 Manuscript under review for journal Biogeosciences Discussion started: 15 February 2018 c Author(s) 2018.…”

“…CC BY 4.0 License. between 9.0 to 3.5 Ma and promote the high quantities of carbonates deposit at the seafloor (Gupta et al, 2004;Dickens and Owen, 1999).…”

“…Carbonate mass accumulation during the Latest Miocene-Early Pliocene at Indo-Pacific provided the bioclastic deposition to the sea floor (Singh et al, 2012;Rai and Singh, 2001;Gupta et al, 2004;Arumugm et al, 2014). These carbonate sediments deposit on the seafloor 15 thus form a favorable environment for benthic fauna (fig 2).…”

“…The presence of Globigerina bulloides indicates that the 5 lithification history of carbonate rocks are less than 5 Ma (Pliocene-Recent) old. Therefore, carbonate deposit on the SWIR should be the bioclastic deposition from the productivity related events 'biogenic bloom' to large part of Indian Ocean during middle Miocene to the early Pliocene (Singh et al, 2012;Rai and Singh, 2001;Gupta et al, 2004;Arumugm et al, 2014).…”

Cenozoic Climatic Record for Monsoonal Rainfall over the Indian Region

“…At the same time aeolian dunes formation and Playa lakes started form after ~8 Ma, suggesting an enclosed desert basin from that time, suggesting that plateau uplift may be causing the regional climatic drying (Zheng et al 2004). Gupta et al (2004) examined the deep-sea benthic foraminiferal census data combined with published data shows that a major increase in biogenic productivity at ~10-8 Ma throughout the Indian Ocean, the equatorial Pacific, and southern Atlantic. The authors suggest that a change has been linked to initiation or intensification of the Indian Ocean monsoons.…”