Increased precipitation and weathering across the Paleocene‐Eocene Thermal Maximum in central China

Abstract

Global warming during the Paleocene-Eocene Thermal Maximum (PETM) 55.5 million years ago (Ma) was associated with a massive release of carbon to the ocean-atmosphere system, as evidenced by a prominent negative carbon isotope excursion (CIE) and widespread dissolution of marine carbonates. The paleohydrologic response to the PETM warming has been studied worldwide; however, relevant records of environmental perturbation in Asia are lacking so far. Here we extend the record of this event in central China, a subtropical paleosetting, through geochemical and mineralogical analyses of lacustrine sediments. Geochemical indicators of authigenic carbonates-including molar Mg/Ca and Sr/Ca ratiossuggest an overall increased precipitation across the PETM, compatible with the disappearance of authigenic dolomite and the appearance of kaolinite in the strata. The relatively humid conditions persisted long after the carbon-cycle perturbation had stopped, implying that the transient hyper-greenhouse warming might have forced the regional climate system into a new climate state that was not easily reversed. Additionally, a gradual increase in chemical index of alteration (CIA) and the appearance of kaolinite are associated with the PETM, indicating an intensified silicate weathering and pedogenesis in the watershed in response to warmer and more humid climate. Our results corroborate the theory that an accelerated continental chemical weathering served as a negative feedback to sequester carbon and lower the atmospheric greenhouse-gas levels during the PETM.

Paleoweathering and paleoenvironmental change recorded in lacustrine sediments of the early to middle Eocene in Fushun Basin, Northeast China

“…A widespread increase in kaolinite content has been observed during the PETM in terrestrial and marine sites worldwide [ Robert and Kennett , ; John et al ., ; Chen et al ., ]. Some researchers ascribe the kaolinite peak to an increased chemical weathering in response to the PETM warming [ Robert and Kennett , ; Chen et al ., ], while others explain it as a signal of enhanced exhumation and reworking of ancient kaolinie‐rich soils [ Thiry and Dupuis , ; John et al ., ]. In addition, the 87 Sr/ 86 Sr values of marine carbonates, which was explained as a proxy for global chemical weathering, do not show marked change from 50 to 40 Ma [ Richter et al ., ].…”

Sensitivity of the Eocene climate to CO<sub>2</sub> and orbital variability

“…The African and Asian monsoon indices are both correlated with the precession index, a well-established feature of Quaternary records (e.g. Cruz et al, 2005). The American monsoon index is fairly strongly correlated with the precession index at high levels of CO 2 and negatively correlated with CO 2 at low levels of CO 2 .…”

Variation of minerals and clay minerals recorded in the Neo-Tethys (central Turkey): new evidence of climatic changes during the middle Eocene

“…A divergence between the d 18 O curves of the shallow-and deep-water dwelling planktonic foraminifera after the event suggests a more stratified water column in the Neo-Tethys. ROBERT; KENNET, 1994;KAIKO et al, 1996;GAWENDA et al, 1999;GIBSON;BYBELL;MASON, 2000;ERNST et al, 2006;SCHULTE;SCHEIBNER;SPEIJER, 2011;SOLIMAN et al, 2011;JOHN et al, 2012;BORNEMANN et al, 2014;PUJALTE;BACETA;SCHMITZ, 2015;CHEN et al, 2016;KEMP et al, 2016). The EECO proxies were identified in the western Pyrenees and in China, also with an increase in kaolinite, however towards the end of the period, dryer conditions may have prevailed ( WANG et al, 2013a;PAYROS et al, 2015).…”

“…Previous studies have used the distribution and abundances of clay minerals assemblages in surface sediments from oceanic basins (BISCAYE, 1965;GRIFFIN;WINDOM;GOLDBERG, 1968;KOLLA;HENDERSON;VENKATARATHNAM;BISCAYE, 1976) and the world oceans (RATEEV et al, 1969;WINDOM, 1976;RATEEV;SADCHIKOVA;SHABROVA, 2008) to establish distribution patterns related to latitudinal climate regimes, weathering conditions, wind regimes, river discharge and ocean currents ( PETSCHICK; KUHN;GINGELE, 1996;X. GINGELE et al, 2002;EHRMANN;SETTI;MARINONI, 2005;ALIZAI et al, 2012;CHEN et al, 2016). Epochs of significant climatic changes, such as the ones observed at the beginning of the Cenozoic Era (e.g.…”

“…The occurrence of other authigenic minerals was discarded mainly due to observations through SEM, which indicated detrital characteristics and no signs of diagenesis. Additionally, sedimentary deposit thickness did not exceed 2 km, which could also induce a diagenetic imprint ( CHAMLEY, 1989;BOLLE, M.;ADATTE, 2001;CHEN et al, 2016). Despite the active tectonics in the region, the Baskil succession is tectonically undisturbed, with very little post-depositional alteration (RODELLI et al, 2017).…”