Chemostratigraphic Constraints on Oligocene–Miocene Sedimentation and Hiatus Formation at IODP Site U1516, Mentelle Basin: Implications for Deep‐Water Circulation in the Eastern Indian Ocean

Abstract The International Ocean Discovery Program (IODP) Expedition 369 recovered high‐quality deep‐sea sediments from Site U1516 in the Mentelle Basin, offshore southwest Australia, spanning back to the Late Cretaceous. Here we present an integrated chemostratigraphic study of the Oligocene–Miocene interval at Site U1516, combining seawater 87 Sr/ 86 Sr ratios with benthic foraminiferal δ 13 C and δ 18 O records to refine the shipboard age model. The studied section, composed mainly of calcareous and nannofossil ooze, extends from 132.7 to 333.7 mbsf. Our results refine previously inferred sedimentary hiatuses and establish a new Sr‐isotope age control point, identifying three major hiatuses at 12.8–16.4 Ma, 22.5–23.1 Ma, and 25.4–26.9 Ma. These hiatuses span major global climate events, including the Middle Miocene Climate Transition (13.8–14.7 Ma), the Miocene Climatic Optimum (14.7–16.9 Ma), Mi1 event (23.03 Ma), and the Late Oligocene Warming (24.0–26.5 Ma). The 87 Sr/ 86 Sr, δ 13 C, and δ 18 O records show strong agreement with global reference curves, supporting the robustness of the revised age model. A key revision is the reassignment of sediments previously attributed to the Middle Miocene (13.183–15.16 Ma) to the Lower Miocene (16.4–22.5 Ma). We interpret these sedimentary hiatuses as reflecting low‐carbonate preservation conditions and enhanced deep‐water circulation associated with global cooling. Our results further suggest that changes in Southern Ocean deep‐water circulation influenced sediment accumulation and preservation in the eastern Indian Ocean during the Oligocene–Miocene.