Where: Liaoning, China (41.4° N, 124.7° E: paleocoordinates 44.5° N, 126.7° E)

• coordinate based on nearby landmark

• small collection-level geographic resolution

When: Lujiatun Member (Yixian Formation), Late/Upper Barremian to Late/Upper Barremian (130.0 - 122.5 Ma)

• Lowest part of Yixian Formation. He et al 2006 give Ar-Ar date of 123.2±1.0 Ma. 'Lujiatun bed'

•The Yixian Formation can be subdivided into five units, in ascending order, Lujiatun unit, Lower Lava, Jianshangou unit, Upper Lava, Dawangzhangzi unit, Jingangshan unit, and Huanghuashan unit. Most of the Jehol fossils from the Yixian Formation are preserved in four beds, that is, the Lujiatun bed (recalculated age is 124.0 ± 1.0/1.3 Ma, He et al., 2006), the Jianshangou bed (125.43 ± 0.50/0.88 Ma, Swisher et al., 1999), the Dawangzhangzi bed, and Jinggangshan bed (~122 Ma, Smith et al., 1995).U-Pb dating suggests that the Huangbanjigou section ranges from 124.9 ± 1.7 Ma to 122.8 ± 1.6 Ma (Yang et al., 2007). Chang et al. (2017) obtained Ar/Ar ages of 125.8 ± 1.0 Ma and 126.0 ± 0.8 Ma from the Lujiatun Unit, the lowest part of the Yixian Formation, below the lacustrine shales.

•He et al. (2004) reported a 40Ar/39Ar age of 120.3 ± 0.7 Ma for a tuff layer in the lower part of the Jiufotang Formation, and Chang et al. (2009) obtained a 40Ar/39Ar age of 122.1 ± 0.3 Ma for a tuff layer from the lowermost part of the Jiufotang Formation. Yu et al. (2021) dated an ash bed just above the Yixian/Jiufotang formation boundary to 122.0 ± 0.9 Ma and three tuff beds from the Xiaotaizi section to 118.9 ± 0.8 Ma, 118.8 ± 0.6 Ma, and 118.6 ± 1.1 Ma. These ages suggest that the Jiufotang Formation in Jianchang Basin was deposited at ca. 122.0–118.9 Ma.

•Olierrok et al. (2019) used a selection of U-Pb and 40Ar-39Ar geochronology to place the Barremian–Aptian boundary (the base of the Chron M0r) between 123.8 and 121.8 Ma. The GTS 2020 uses an age of 121.4 Ma for the base of the Aptian, and multiproxy orbital tuning gives an age of 120.2 Ma for the Barremian-Aptian boundary (Leandro et al., 2022). Therefore, the Yixian Formation should be entirely Late Barremian, with the Jiufotang Formation deposited in the Early Aptian (or latest Barremian at its base).

• bed-level stratigraphic resolution

Environment/lithology: fluvial; lithology not reported

Size class: macrofossils

Reposited in the IVPP

Collection methods: mechanical,

Primary reference: X. Xu, M. A. Norell, X.-l. Wang, P. J. Makovicky, and X.-c. Wu. 2002. A basal troodontid from the Early Cretaceous of China. Nature 415:780-784 [M. Carrano/M. Carrano/J. Alroy]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 55685: authorized by Matthew Carrano, entered by Kaitlin Maguire on 02.11.2005, edited by Roger Benson

Creative Commons license: CC BY (attribution)