Further Support for a Cretaceous age for the Feathered-Dinosaur Beds of Liaoning, China: new 40Ar/39Ar Dating of the Yixian and Tuchengzi Formations

Chinese Science Bulletin (Impact Factor: 1.58). 01/2002; 47(2):136-139. DOI: 10.1360/02tb9031


We report new 40Ar÷39Ar dating results obtained from total fusion and incremental-heating analyses of sanidine and biotite from three tuffs found
interbedded within the fossil-bearing deposits of Liaoning, northeast China. The first is a new sample of the Bed 6 Sihetun
tuff from the Yixian Formation, previously dated by our team as middle Early Cretaceous, and recently considered by Lo et
al., partially reset due to metamorphism from a nearby basaltic sill. The second is the Yixian Bed 9 tuff from Hengdaozi considered
by Lo et al. to be unaffected by metamorphism and whose age, based on total fusion 40Ar÷39Ar dating of biotite, argues for a Jurassic age for the Yixian Formation. The third tuff is a previously undated tuff from
the upper part of the underlying Tuchengzi Formation. Single crystal total fusion 40Ar÷39Ar analyses of the Sihetun sanidine showed homogeneous radiogenic Ar, Ca÷K ratios, excellent reproducibility and gave a mean
age of 125.0±0.18 (1SD)±0.04 (SE) Ma. Single sanidine crystal total fusion 40Ar÷39Ar analyses of the Hengdaozi tuff gave a mean age of 125.0±0.19 (1SD)±0.04 (SE) Ma, which is indistinguishable from the Sihetun
tuff. The Tuchengzi Formation tuff gave a mean age of 139.4±0.19 (1SD)±0.05 (SE) Ma. Detailed laser incremental-heating analyses
of biotite from Sihetun, Hengdaozi, and Tuchengzi tuffs show disturbed Ar release patterns and evidence of trapped argon components.
We conclude from these analyses that the total fusion dates on biotite by Lo et al. are erroneously old and isotopic dating
of both biotite and sanidine from tuffs of the Yixian Formation point to a middle Early Cretaceous age. The upper part of
the Tuchengzi Formation can be referred to the Early Cretaceous.

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    • "The age data for the Chengde–Beijing region are cited from Niu et al. (2004), He et al. (2006), Zhang et al. (2005b, 2008b), Zhao et al. (2006b), and Liu et al. (2012). Data for the western Liaoning Province are from Swisher et al. (2002), Zhang et al. (2005a, 2009), He et al. (2006), Yan et al. (2006), and Yang and Li (2008). Data for the Luxi area are from Qiu et al. (2002), Zhu et al. (2010), Li et al. (2013), Xu et al. (2013b), and this study. "
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    ABSTRACT: Provenances of sedimentary rocks may provide important constraints on the tectonic evolution of the North China Block (NCB). Previous studies have demonstrated that the northern NCB (NNCB) and the Xing-Meng orogenic belt (XMOB) supplied massive detritus southward into the hinterland of the NCB during the Jurassic. In order to study the evolution of sedimentary provenance during the Middle–Late Mesozoic, U–Pb geochronology and Hf isotopic geochemistry of detrital zircon grains and chemical compositions of detrital garnets from sandstones in the Luxi and Jiaolai areas, eastern NCB, were analyzed in combination with published data on the Jurassic sandstones. The Late Paleozoic–Mesozoic (367–139 Ma) zircons in the lowermost Cretaceous Mengyin Formation samples from the Luxi area show eHf(t) values of À15.3 to À3.2 and +1.3 to +10.0, which are very similar to the results of analyses of the Jurassic formations. Further, the increased amount of Mesozoic zircons and granulite-derived garnets in the Mengyin Formation samples, compared to those in the Jurassic samples, indicates there was more detri-tus supply from the NNCB than from the XMOB. In the overlying Qingshan Formation samples, zircon grains do not exhibit Paleozoic ages, but most of them have Early Cretaceous ages and negative eHf(t) values, which are similar to the zircon grains extracted from the widespread Early Cretaceous igneous rocks in the NCB. This suggests that the provenance might have changed to a locally derived source. In contrast, the zircon population of the Early Cretaceous sandstones from the Jiaolai basin is dominated by grains of mid-Neoproterozoic age (700–900 Ma) which signifies contribution from the Sulu orogen. Moreover, the detrital garnet assemblages of sandstones in the Luxi area are not consistent with those from representative metamorphic rocks in the Sulu orogen. The above results seem to confirm that the Mesozoic sedimentary provenance of the Luxi area had no evident connection with the Sulu orogen. Instead, the differential uplifting and exhumation of deep crustal rocks in the NNCB and the XMOB, associated with closure of the Mongol–Okhotsk Ocean, might exert a dominant control on sedimentary provenances in the wide hinterland of the NCB from the Jurassic period to ~ 136 Ma (the upper boundary age of the Mengyin Formation).
    Full-text · Article · Jul 2015 · Journal of Asian Earth Sciences
    • "Barremian to early Aptian stages of the Early Cretaceous (126.1–124.6 Ma) (Barrett, 2000; Chen et al., 2005; Gradstein et al., 2012; Makarkin et al., 2012; Swisher et al., 2002 "
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    ABSTRACT: The Early Cretaceous Yixian Formation from western Liaoning in northeastern China is well known for its extremely high diversity of plant macrofossils including important basal members of the Gnetales. The Gnetales from the Yixian Formation currently play a significant role in our present understanding of evolution and adaptation within the group. In the present paper the ephedroid macrofossil genus Prognetella Krassilov et Bugdaeva previously known from the Early Cretaceous of Transbaikalia in southern Russia is revised based on additional specimens from the Yixian Formation. Baicarpus Gang Han et al., a recently described genus interpreted as an angiosperm is reduced to synonymy and reinterpreted as a member of the Gnetales, and placed within the genus Prognetella. Reproductive shoots of Prognetella consist of nodes and internodes, and each of these constitutes a lax compound female spike; foliar bracts are paired at each node, and each foliar bract usually encloses a reproductive unit; the paired female reproductive units together with their subtending bracts and the supporting peduncle constitute a diaspore. The diaspore was abscised from the lower node and disseminated when the plant ripened. A cladistic analysis was conducted based on morphological characters of reproductive organs to understand the evolution of early Ephedraceae. The result suggests that Prognetella is transitional between the genera Siphonospermum Rydin et Friis and Chengia Yang et al. and further illustrates the reduction and sterilization hypothesis previously proposed within the Ephedraceae. In addition, this study discovered a new and unusual dispersal mechanism within the basal members of the Ephedraceae.
    No preview · Article · Jun 2015 · Perspectives in Plant Ecology Evolution and Systematics
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    • "The stratigraphic and geographic location of other specimens reported as belonging to Hongshanornis longicresta has not been provided in the publications that make reference to these specimens (Li, Zhou & Clarke, 2011; Zheng et al., 2011). The holotype of Parahongshanornis chaoyangensis (PMOL-AB00161) is from the younger Jiufotang Formation in Yuanjiawa Town, Chaoyang City (Liaoning Province, China) (Li, Zhou & Clarke, 2011), thus this specimen is 3 to 5 million years younger (see Swisher et al., 2002; Yang, Li & Jiang, 2007; Chang et al., 2009) than the Yixian hongshanornithids and separated by approximately 100 km from either Dawangzhangzi or Shifo. "
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    ABSTRACT: The discovery of Hongshanornis longicresta, a small ornithuromorph bird with unusually long hindlimb proportions, was followed by the discovery of two closely related species, Longicrusavis houi and Parahongshanornis chaoyangensis. Together forming the Hongshanornithidae, these species reveal important information about the early diversity and morphological specialization of ornithuromorphs, the clade that contains all living birds. Here we report on a new specimen (DNHM D2945/6) referable to Hongshanornis longicresta that contributes significant information to better understand the morphology, trophic ecology, and aerodynamics of this species, as well as the taxonomy of the Hongshanornithidae. Most notable are the well-preserved wings and feathered tail of DNHM D2945/6, which afford an accurate reconstruction of aerodynamic parameters indicating that as early as 125 million years ago, basal ornithuromorphs had evolved aerodynamic surfaces comparable in size and design to those of many modern birds, and flight modes alike to those of some small living birds.
    Full-text · Article · Jan 2014 · PeerJ
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