New Paleomagnetic and Stable‐Isotope Results from the Nanxiong Basin, China: Implications for the K/T Boundary and the Timing of Paleocene Mammalian Turnover

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The University of Chicago Press is collaborating with JSTOR to digitize, preserve and extend access to The Journal of Geology. A B S T R A C TThe Nanxiong Basin (Guangdong Province, China) preserves the most complete Asian stratigraphic record of the Cretaceous-Paleogene (K/Pg) boundary extinction and the subsequent Paleocene mammalian radiation. Despite extensive study, the precise placement of the K/Pg boundary in the Nanxiong Basin sequence has been controversial, and the timing of subsequent mammalian turnover is poorly constrained. We present new paleomagnetic and geochemical data from the Late Cretaceous Pingling Formation (Nanxiong Group) and the overlying Paleocene Shanghu, Nongshan, and Guchengcun formations (Luofozhai Group). Our samples are directly correlated with previous geochemical and paleontological sampling localities, allowing for easy comparison with other local proxy records. Results indicate that the traditional placement of the K/Pg boundary at the base of a chaotic channel sandstone bed marking the highest stratigraphic appearance of dinosaur eggshell fragments and lowest stratigraphic appearance of Paleocene mammalian fossils lies about two-thirds of the way up Chron C29R, consistent with the placement of the boundary in all other well-documented sections. The average carbon isotope composition of paleosol carbonates decreases by 12‰ in the Early Paleocene, consistent with a major disruption to global carbon cycling after the K/Pg boundary. Constraints on the age of the first major Cenozoic mammalian turnover event in Asia (the Shanghuan-Nongshanian Asian Land Mammal Age boundary) support its placement near the top of Chron C27N, which coincides with a similar turnover in North America and geochemical changes recorded in several deep sea cores.

New age constraints for the Salamanca Formation and lower Rio Chico Group in the western San Jorge Basin, Patagonia, Argentina: Implications for Cretaceous-Paleogene extinction recovery and land mammal age correlations

“…62-60 Ma) age that it was previously assigned (Marshall et al, 1981;Somoza et al, 1995;Bonaparte et al, 1993;Gelfo et al, 2009). The Peligran SALMA is then correlative with the early Torrejonian North American Land Mammal Age (NALMA) and Shanghuan Asian Land Mammal Age (ALMA; Clyde et al, 2010). These results also imply that the Peligran SALMA is closer in age to (or possibly older than) the Tiupampan SALMA.…”

The Palaeocene “top chron C27n” transient greenhouse episode: evidence from marine pelagic Atlantic and peri‐Tethyan sections

“…, 2006). It is also striking that in the continental realm, a major faunal turnover (Shanghuan/Nongshanian Asian land mammal boundary, which is synchronous with the North American Torrejonian–Tiffanian boundary) occurs at the C27n/C26r boundary (Clyde et al. , 2008, 2010; Ting et al.…”

Early Paleogene stratigraphic sequences, mammalian evolution and its response to environmental changes in Erlian Basin, Inner Mongolia, China

“…Early paleomagnetic work did not focus on the age constraints of related land mammal ages [3,26,63,64]. In recent years, paleomagnetic works aiming at age constraints for Paleocene land mammal ages have been conducted in several basins in southern China [65,66]. The time intervals for other Paleogene land mammal ages were mainly based on intercontinental biostratigraphic correlations with North American Paleogene [4,7,10,11].…”

“…Currently, the Paleocene NongshanianGashatan boundary has not been precisely determined due to a poor section of deposits at this boundary level. However, the paleomagnetic study in both the Chijiang Basin, Jiangxi and the Nanxiong Basin, Guangdong proves that the Nongshanian strata are mainly within Chron C26r [65,66], while the paleomagnetic result in the Huheboerhe area indicates that the lower horizon containing the Gashatan mammals (NM-1) is in the lower part of the Chron C25r [17]. The Nongshanian-Gashatan boundary can be provisionally put at the base of Chron C26n.…”