Astronomical pacing of the global silica cycle recorded in Mesozoic bedded cherts

Abstract

The global silica cycle is an important component of the long-term climate system, yet its controlling factors are largely uncertain due to poorly constrained proxy records. Here we present a ∼70 Myr-long record of early Mesozoic biogenic silica (BSi) flux from radiolarian chert in Japan. Average low-mid-latitude BSi burial flux in the superocean Panthalassa is ∼90% of that of the modern global ocean and relative amplitude varied by ∼20–50% over the 100 kyr to 30 Myr orbital cycles during the early Mesozoic. We hypothesize that BSi in chert was a major sink for oceanic dissolved silica (DSi), with fluctuations proportional to DSi input from chemical weathering on timescales longer than the residence time of DSi (<∼100 Kyr). Chemical weathering rates estimated by the GEOCARBSULFvolc model support these hypotheses, excluding the volcanism-driven oceanic anoxic events of the Early-Middle Triassic and Toarcian that exceed model limits. We propose that the Mega monsoon of the supercontinent Pangea nonlinearly amplified the orbitally paced chemical weathering that drove BSi burial during the early Mesozoic greenhouse world.

Constraints on the duration of the early Toarcian T-OAE and evidence for carbon-reservoir change from the High Atlas (Morocco)

“…The Talghemt section is the first cyclostratigraphic record from the High Atlas of both Pl-To and T-OAE events, possibly owing to its specific sedimentary environment (Section 1.1). The duration of 300-500 kyr of the T-OAE is also supported by Ikeda et al (2017Ikeda et al ( , 2018 from deep-sea sedimentray successions in Japan. Finally, this shorter duration is compatible with carbon-cycle modeling of the magnitude of CIE (e.g., Beerling and Brentnall, 2007;Them et al, 2017a), but also with numerical modeling of other geochemical cycles (e.g., Them et al, 2017a).…”

Sedimentary process of the bedded chert in the Mino Belt, central Japan: Three problems

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Astronomical cycles recorded in the sedimentary rhythms of deep-sea bedded chert and its significance on biogeochemical cycle

“…, Hays et al, 1976; Fig. 1 cyclostratigraphy , Fischer et al, 1988;Hinnov, 2013 Astrochronology , Hays et al, 1976;Hinnov and Hilgen, 2012 , Hilgen, 2012 --, Hays et al, 1976;Zachos et al, 2001 , Hinnov andOgg, 2007;Hinnov, 2013Hinnov and Hilgen, 2012総 説 1970Yao et al, 1980Matsuda and Isozaki, 1991;Isozaki, 2014 Matsuda andIsozaki, 1991 /1000 1 Matsuda and Isozaki, 1991;Isozaki, 2014, Isozaki, 2014Fischer, 1976Hori et al, 1993, , Hori et al, 1993, 1 Hori et al, 1993 1-2 1-2 Hori et al, 1993Hinnov, 2013Ikeda and Hori, 2014Ikeda et al, 2017 Latemar Hinnov and Goldhammer, 1991 U-Pb Fig. . Earth s orbital parameters, summer insolation at 65° north, and oxygen isotope records of benthic foraminifera (LR04; Lisiecki and Raymo, 2005).…”

“…Mundil et al, 1996;Wotzlaw et al, 2017% Hinnov, 20132 Laskar et al, 2004Fig. 1 Hays et al, 1976OAE Algeo et al, 2010Ikeda et al, 2010Ikeda et al, , 2015Ikeda et al, , 2016Ikeda et al, , 2017Ikeda et al, , 2018Ikeda andTada, 2013, 2014;Ikeda and Hori, 2014;Zhang et al, 2014;Meyer and Malinverno, 2018 Laskar et al, 2004). The red, yellow green, dark green, and blue contour levels are chosen such that 75%, 50%, 25%, and 5% of the wavelet power is above each level, respectively.…”

“…model (B) Carbonate carbon isotope and organic carbon burial flux. (C) Combined flux of CO 2 degassing and organic carbon weathering calculated from modified GEOCARBSULFvolc between 250 Ma and 180 Ma (modified afterIkeda et al, 2017). Periods of (D) LIPs and (E) main oceanic anoxic events (OAEs) are also shown.…”