Further Support for a Cretaceous age for the Feathered-Dinosaur Beds of Liaoning, China: new 40Ar/39Ar Dating of the Yixian and Tuchengzi Formations
ABSTRACT 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.
Full-textDOI: · Available from: Yuan Wang, Sep 26, 2015
- SourceAvailable from: Jianqiang Xu
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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. "
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).Journal of Asian Earth Sciences 01/2015; DOI:10.1016/j.jseaes.2015.07.008 · 2.74 Impact Factor
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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. "
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.PeerJ 01/2014; 2:e234. DOI:10.7717/peerj.234 · 2.11 Impact Factor
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- "The Yixian Formation is widely distributed in West Liaoning , and its geological age is the early Aptian—earliest late Aptian of the Early Cretaceous, which can be correlated by radiometric dating to about 120—125 Ma –. Previously, this formation has yielded a plethora of extraordinarily well-preserved freshwater and terrestrial fossils, especially including early angiosperms (e.g., Archaefructus liaoningensis Sun et al.), feathered theropod dinosaurs, early seed-eating birds, and primitive mammals –, –. "
ABSTRACT: Bracts of female cones of extant gymnosperm Ephedra (Joint fir) are either colorful and fleshy (section Ephedra), or dry-winged and membranous (section Alatae), or dry and coriaceous (section Asarca), which have played a crucial role in long-distance seed dispersal that is responsible for a wide distribution of the genus in semiarid and arid areas of Eurasia, North Africa, North America, and South America. Recent molecular systematic studies on Ephedra have suggested that the fleshy bracts in character evolution may be plesiomorphic relative to the dry, membranous and coriaceous bracts. However, little is known about when the fleshy bracts of Ephedra have made their debut in the geological past. Herein, we describe a novel, fleshy bract-bearing female cone macrofossil from the Early Cretaceous (ca. 120-125 Ma) Yixian Formation in Liaoning, northeastern China. This cone bears three ellipsoid seeds subtended by only one whorl of fleshy bracts. Each seed has a thin outer envelope and an inner integument that extends upward and passes through the opening of the outer envelope, forming a thin and straight micropylar tube. Such a syndrome shows the closest similarity to an extant triovulate species Ephedra intermedia in the section Ephedra, but the latter bears a whorl of terminal fertile bracts and more than one whorl of inferior sterile bracts, and a thick outer envelope. Hence, we establish a new fossil species Ephedra carnosa. Our discovery provides the first direct macrofossil evidence for the previous molecular systematics of Ephedra, implying that the origin of fleshy bracts in Ephedra should not have been later than that of the membranous and coriaceous bracts by at least the Early Cretaceous.PLoS ONE 10/2013; 8(1):e53652. DOI:10.1371/journal.pone.0053652 · 3.23 Impact Factor