Timing and preservation mechanism of deglacial pteropod spike from the Andaman Sea, northeastern Indian Ocean

• Published in: Boreas
• Main Authors: Sijinkumar, Adukkam V., Nath, Bejugam N., Guptha, Medimi V. S., Ahmad, Syed M., Rao, Bandaru R.
• Other Authors: CSIR (Govt. of India) XII Plan funded Project GEOSINKS to NIO, Goa
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2014
• Subjects: Indian; Ocean acidification
• Online Access: http://dx.doi.org/10.1111/bor.12099; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fbor.12099; https://onlinelibrary.wiley.com/doi/pdf/10.1111/bor.12099

The aragonite compensation depth ( ACD ) fluctuated considerably during the last glacial until the H olocene with a dominant pteropod preservation spike during the deglacial period, which is prominently seen in three well‐dated cores covering the A ndaman S ea, northeastern I ndian O cean. The precise time period of the preservation spike of pteropods is not known but this knowledge is crucial for stratigraphical correlation and also for understanding the driving mechanism. Isotopic and foraminiferal proxies were used to decipher the possible mechanism for pteropods preservation in the A ndaman S ea. The poor preservation/absence of pteropods during the H olocene in the A ndaman S ea may have implications for ocean acidification, driven by enhanced atmospheric CO 2 concentration. Strengthening of the summer monsoon and the resultant high biological productivity may also have played a role in the poor preservation of pteropods. The deglacial pteropod spike is characterized by high abundance/preservation of the pteropods between ∼19 and 15 cal. ka BP, associated with very low atmospheric CO 2 concentration. Isotope data suggest the prevalence of a glacial environment with reduced sea surface temperature, upwelling and enhanced salinity during the pteropod preservation spike. Total planktic foraminifera and G lobigerina bulloides abundances are low during this period, implying a weakened summer monsoon and reduced foraminiferal productivity. Based on the preservation record of pteropods, it is inferred that the ACD was probably deepest (>2900 m) at 16.5 cal. ka BP . The synchronous regional occurrence of the pteropod preservation spike in the A ndaman S ea and in the northwestern Indian Ocean could potentially be employed as a stratigraphic marker.