“Tertiary Dinosaurs” in the Nanxiong Basin, Southern China, Are Reworked from the Cretaceous

Abstract

The Nanxiong and Shanghu Formations of southeastern China span the KT boundary interval and preserve an important paleontological record. A 1285-m section across the KT boundary was measured, and lithological units were documented and sampled. Strata were deposited in alluvial fan/playa mudflat environments in a highly seasonal, semiarid climate. Previous workers placed the KT boundary at the Nanxiong/Shanghu formational contact. The uppermost Nanxiong and lowermost Shanghu Formations contain an assemblage of dinosaur egg fragments and Tertiary fossils, which led to the notion that dinosaurs survived into the Paleocene. On the basis of our results, we argue that the mixed KT assemblage is a result of debris flows reworking Cretaceous fossils. Depositional environments and paleoclimate did not change significantly across the KT boundary.

Early Mississippian sandy siltstones preserve rare vertebrate fossils in seasonal flooding episodes

“…Examples of deposits that contain similarly high concentrations of vertebrate microfossils are the Upper Cretaceous Conor's Microsite, a siltstone‐rich crevasse‐splay deposit with clay clasts (Wilson, ); and fine‐grained microsite deposits from the Upper Cretaceous Judith River Formation with bivalves, interpreted as autochthonous pond/lake deposits (Rogers & Brady, ). Clay‐pebble conglomerates with 2 mm to 8 cm sized clasts composed of sand and granule sized mud aggregates from the Cretaceous–Tertiary of the Nanxiong Basin, Southern China, are interpreted as distal sheetfloods (Buck et al ., ). These deposits may be similar to the discontinuous conglomerates of the Ballagan Formation.…”

“…Microsites (concentrations of disarticulated vertebrate microfossils where 75% of vertebrate skeletal elements are ≤5 cm in size), specifically those which occur in fine‐grained sediments (Wilson, ; Rogers & Brady, ), may be similar deposits, although their detailed sedimentology has not been examined. Other similar deposits are mud aggregates (sand grain‐sized clay aggregates: Rust & Nanson, ) and clay–pebble conglomerates (Buck et al ., ).…”

“…Fine‐grained mudstone or siltstone overbank facies from floodplain successions preserved in the sedimentary record commonly contain concentrations of vertebrate macrofossils and microfossils (Buck et al ., ; Wilson, ). Tetrapod fossils commonly occur in fluvial conglomerate lags and overbank deposits: a review of Euramerican Pennsylvanian tetrapod sites identified swampy pools, oxbow lakes and abandoned fluvial channels filled with organic material as the most common environments where fossils are preserved (Milner, ).…”

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

“…This interpretation (the "Stets placement") implies the survival of dinosaurs into the Paleogene and thus argues against a globally synchronized mass extinction coincident with an impact event. Later, Buck et al (2004) accepted the Stets placement but argued that the dinosaur remains above that level were reworked because of debris flows in the upper Pingling Formation (their "Nanxiong Formation") and the lower Shanghu Formation. Taylor et al (2006) reviewed the entire suite of evidence and concluded that the preponderance of evidence supports the Zhao placement.…”

Cenozoic dinosaurs in South America – revisited

“…The dating errors were almost always due to reworked fossils, material that had recently experienced time-averaging across the Cretaceous-Paleogene boundary. Such instances are known from France (Buffetaut et al, 1980), China (Buck et al, 2002), and the western interior of North America (Argast et al, 1987;Lofgren, 1995;Renne and Goodwin, 2014). Basal Danian, that is post-Cretaceous, nonavian theropod bones have been reported from the Chatham Islands, New Zealand (Stilwell et al, 2006;Stilwell and Håkansson, 2012).…”