Terrestrial responses of low-latitude Asia to the Eocene–Oligocene climate transition revealed by integrated chronostratigraphy

Abstract

Abstract. The Paleogene sedimentary records from southern China hold important clues to the impacts of the Cenozoic climate changes on low-latitudes. However, although there are extensive Paleogene terrestrial archives and some contain abundant fossils in this region, few are accurately dated and have a temporal resolution adequate to decipher climate changes. Here we present a detailed stratigraphic and paleomagnetic study of a fossiliferous late Paleogene succession in the Maoming Basin, Guangdong Province. The succession consists of oil shale of the Youganwo Formation (Fm) in the lower part and massive pebbly coarse sandstones of the overlying Huangniuling Fm in the upper part. The conformable transition from oil shale to sandstones represents a major depositional environmental change from a lacustrine to a deltaic environment. The substantially refined chronostratigraphic framework is established based on the litho-, bio-, cyclo-, and magnetostratiphic data that place the environmental transition at 33.88 Ma, coinciding with the Eocene–Oligocene climate transition (EOT) at ~ 33.7 to ~ 33.9 Ma. We suggest that the transition from a lacustrine to deltaic environment in Maoming Basin represents terrestrial responses to the EOT and indicates a significant reduction in hydrodynamics in low-latitude regions during the global cooling at EOT.

Orbital climate variability on the northeastern Tibetan Plateau across the Eocene–Oligocene transition

“…The long-term trend in our records confirms previous inferences about Asian aridification and cooling across the EOT 9,14,[16][17][18][19][20][21]23 . The higher resolution of our records constrains more precisely the age of the main transition to~33.7 Ma, around the C13r-C13n boundary, which corresponds with the Oi-1 event (33.8-33.6 Ma) in high-resolution marine benthic δ 18 O and δ 13 C records 5,52 , and post-dates the initial EOT-1 event at 34.1-33.9 Ma (Fig.…”

“…As summarized in a flowchart of our orbital tuning strategy ( Supplementary Fig. 20), we conclude that the orbital response shift identified at~33.7 Ma in the Lanzhou Basin χ lf record is a robust feature of Asian climate reorganization across Oi-1, which is supported by (1) the Maoming cyclostratigraphy 19 and spectral analyses of (2) the Lanzhou Basin χ lf record in the depth domain ( Supplementary Fig. 14), and in astronomical and magnetostratigraphic time scales ( Fig.…”

“…19). Furthermore, the Maoming Basin (South China) lithological record has strong latest Eocene eccentricity cycles 19 . Thus, the Lanzhou Basin χ lf and Pacific benthic δ 18 O records suggest that NE Tibetan Plateau and global changes were consistently paced by eccentricity both before and after the onset of major Antarctic glaciation, consistent with the heartbeat of the Earth system as paced by eccentricity cycles 11,30,31,47 .…”

“…Terrestrial EOT records are relatively rare and include a few from East Asia (Maoming, Xining, Qaidam, and Junggar basins, and Mongolia) 9,14,[16][17][18][19][20][21][22][23] , central North America 13,24 , southernmost South America 25 , and Northern Europe 26 ( Supplementary Fig. 1).…”

“…These studies suggest that the terrestrial playapalaeolake sequences on the NE Tibetan Plateau provide sensitive archives of past climate changes on land and have the potential to reveal details of orbital-scale terrestrial responses to global events through the EOT. At present, analysis of both marine 15,29 and terrestrial 9,13,14,[16][17][18][19][20][21]23,25,26 records has focused primarily on general long-term cooling and/or aridification trends across the EOT, but much less on orbital-scale climate variability 4,9,11,12,16,[30][31][32] , because of a lack of sufficiently high-resolution palaeoclimate records that span continuously from the late Eocene to early Oligocene.…”