Ma, ChaoHinnov, Linda A.Eldrett, James S.Meyers, Stephen R.Bergman, Steven C.Minisini, DanielLutz, Brendan2022-03-242022-03-242021Ma, Chao, Hinnov, Linda A., Eldrett, James S., et al.. "Centennial to millennial variability of greenhouse climate across the mid-Cenomanian event." <i>Geology,</i> 50, no. 2 (2021) The Geological Society of America: 227-231. https://doi.org/10.1130/G48734.1.https://hdl.handle.net/1911/112046Centennial- to millennial-scale climate variations are often attributed to solar forcing or internal climate system variability, but recognition of such variations in the deep-time paleoclimate record is extremely rare. We present an exceptionally well-preserved, millimeter-scale laminated marlstone from a succession of precession-driven limestone-marlstone couplets deposited in the Western Interior Seaway (North America) immediately preceding and during the Cretaceous mid-Cenomanian event (ca. 96.5 Ma). Sedimentological, geochemical, and micropaleontological data indicate that individual pairs of light-dark laminae record alternations in the extent of water-column mixing and oxygenation. Principal component analysis of X-ray fluorescence element counts and a grayscale scan of a continuous thin section through the marlstone reveal variations with 80–100 yr, 200–230 yr, 350–500 yr, ∼1650 yr, and 4843 yr periodicities. A substantial fraction of the data indicates an anoxic bottom water variation with a pronounced 10,784 yr cycle. The centennial to millennial variations are reminiscent of those found in Holocene total solar irradiance variability, and the 10,784 yr anoxia cycle may be a manifestation of semi-precession-influenced Tethyan oxygen minimum zone waters entering the seaway.engThis paper is published under the terms of the CC-BY license.Journal articleg48734-1https://doi.org/10.1130/G48734.1