Extended Data Fig. 2: Stratigraphic correlation of the Cenomanian-Turonian boundary interval at IODP Site U1516 to the Portland Core near the base Turonian Global Stratotype Section and Point (GSSP) in Colorado, USA.
From: Abrupt episode of mid-Cretaceous ocean acidification triggered by massive volcanism
Oceanic Anoxic Event 2 (OAE2) is defined by a positive carbon isotope (δ13C) excursion (grey shading). The correlation is based on: 1) the base and termination of the δ13C excursion27, 2) the anomalously high 192Os abundance interval (light purple dashed line) linked to large igneous province (LIP) volcanic activity19, 3) the base of the initial osmium isotope (187/188Osi) excursion associated with LIP volcanism at the base of OAE219, and 4) bandpassed ~100 kyr-short eccentricity cycles. Calcareous nannofossil biostratigraphy independently supports the correlation as the CC10a/CC10b subzone boundary, approximated by the last occurrence (LO) of Axopodorhabdus albianus, falls in the carbonate barren interval at Site U151627 and lower OAE2 interval in Portland Core109. Site U1516 data sources: δ13C data27, Os data and and cyclostratigraphy (this study). Portland Core data sources: Os data20, δ13C data16 (figure adapted from17). kcps = kilocounts per second; VPDB = Vienna Peedee Belemnite scale; ppt = parts per trillion; CCD = calcite compensation depth.
