Reconstructing Eocene Eastern Indian Ocean Dynamics Using Ocean‐Drilling Stratigraphic Records. Issue 2 (18th February 2021)

• Record Type: Journal Article
• Authors: Xu, Ke; De Vleeschouwer, David; Vahlenkamp, Maximilian; Yang, Renchao; Chen, Honghan
• Is Part Of: Paleoceanography and paleoclimatology. Volume 36:Issue 2(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-02-18
• Subjects: Eastern Indian Ocean -- Eocene -- obliquity forcing -- sea level -- sedimentary noise; Paleoceanography -- Periodicals; Paleoclimatology -- Periodicals; 551.46
• DOI: 10.1029/2020PA004116
• Languages: English
• ISSNs: 2572-4517

Abstract

Abstract: The Eocene Epoch corresponds to the runup toward the Greenhouse to Icehouse Cenozoic transition. To fully appreciate this climate evolution, detailed and accurate age‐depth models are required. While much progress has been made recently in the field of Eocene astrochronology, the construction of unambiguous Eocene astronomical timescales (ATS) is hampered by lithologically undetected hiatuses, the scarcity of carbonate‐rich marine successions, and conflicting cyclostratigraphies. In this study, we present an orbital‐scale cyclostratigraphy for Ocean Drilling Program (ODP) Hole 762C, and we reconstruct Eastern Indian Ocean dynamics. This reconstruction is based on two ocean‐drilling Eocene sequences: ODP Hole 762C and International Ocean Discovery Program (IODP) Site U1514. Our eccentricity‐based cyclostratigraphy for Hole 762C is integrated with existing bio and magnetostratigraphies and constitutes the most precise available chronology for this legacy site. The Hole 762C stratigraphy is combined with the existing Site U1514 age‐depth model to obtain a high‐resolution Eocene ATS for the Eastern Indian Ocean. We apply sedimentary noise modeling to obtain new insights in benthic turbulence at both sites. Despite the significant difference in paleo‐waterdepth, noise levels at both sites carry a 1.2‐Myr obliquity amplitude imprint. We interpret the sedimentary noise at Hole 762C, on a submarine plateau, in terms of sea‐level change. The sedimentary noise at U1514, by contrary, is interpreted to be modulated by bottom current intensity as this site represents a deep‐sea basinal environment. We conclude that, despite very similar astronomical signatures, the mechanistic pathways between astronomical forcing and sedimentary response were radically different at these two sites. Key Points: Cyclostratigraphy applied to two Eocene Indian Ocean scientific drilling records reveals the fingerprint of orbital eccentricity Sedimentary noise at both sites contains a 1.2‐Myr obliquity imprint, albeit in antiphase: Mechanisms causing noise are thus different While sea‐level change causes noise at shallower sites, bottom current intensity might introduce sedimentary noise at deep‐ocean sites