A new protosuchian crocodile from the Upper Triassic Elliot Formation of South Africa

A new protosuchian crocodilian, Baroqueosuchus haughtoni from the Upper Triassic or Lower Jurassic Elliot Formation of the Orange Free State is the most primitive protosuchian crocodilian known. There are no contacts between the quadrate and opisthotic or below the crania-quadrate canal, the internal carotid arteries were not enclosed in separate foramina and the basicranium was flat, with the basisphenoid being broadly exposed on the base of the skull. The basic diagnosis of the Order Crocodilia is discussed and a new diagnosis is offered based upon cranial anatomy.National Science Foundation, USA; Geology Foundation UT Austin, Texas, US

Integrated Diagenesis Study of Tight Gas Sandstone: The Permian Lower Shihezi Formation, Northern Ordos Basin, China

AbstractDiagenesis varies greatly from basin to basin and has been considered as the key control of the reservoir quality of tight sandstones. In this study, we analyzed the petrographic characteristics, diagenesis, and pore types and characteristics of the Permian Lower Shihezi Formation in the Ordos Basin. Results show that most of sandstones are litharenites with minor sublitharenites and feldspathic litharenites. The tight sandstones have ultralow permeabilities (averaging 0.67 mD) and porosities (averaging 8.35%), with pore-throat sizes ranging from 0.035 to 13.29 μm with 94.12% less than 5 μm. Overall, the tight sandstone reservoirs have undergone complex diagenetic alteration. Compaction and clay mineral cements are the two crucial diagenetic factors that controlled the tightness of the reservoirs. The compaction destroyed most of primary porosity, and the effective pores are mainly dissolved micropores, intragranular dissolved micropores, and micropores in clay minerals and mineral grains. The chlorite coating might have helped preserve a certain amount of porosity, but pore-lining chlorites significantly obstructed pore throats and reduced permeability. Results of the study provide insights and direct implications for the future success of exploration and production of the tight gas sandstone in the Ordos Basin and other similar tight sandstone reservoirs

Orbital cycle records in shallow unconsolidated sediments: implications for global carbon cycle and hydrate system evolution in deep-sea area sediments of the Qiongdongnan Basin

IntroductionMilankovitch theory has extensive application in sequence stratigraphy and the establishment of time scales. However, it is rarely applied to shallow strata rich in hydrates. Cyclostratigraphic analysis of the Quaternary unconsolidated sediments can help identify climate and sea level changes that correspond to orbital cycles and improve our understanding of the dynamic evolution of hydrates.MethodsUsing the natural gamma-ray log data from the deepwater area well W01 in the Qiongdongnan Basin, Milankovitch cycle analysis was conducted to identify the primary astronomical period in W01. Anchored to existing AMS-14 C age from bivalve shell as reference point, an astronomical age scale of W01 was established. Simultaneously, through the analyses of major trace elements and total organic carbon content (TOC) in sediment samples, how astronomical orbital cycles influenced past environmental conditions. Furthermore, employing sedimentary noise models, the relative sea level change of well W01 was reconstructed.ResultsSedimentary cycles of 27.34 m and 6.73 m were identified in the GR data from well W01, corresponding to orbital periods of 405 kyr and 100 kyr eccentricity, with a duration of approximately 2.5 Myr. The spectral analysis of paleoenvironmental proxies reveals a sedimentary cycle of approximately 27 m, while the sedimentary noise model reconstructs the fluctuating rise in sea level change. An obliquity modulation period of approximately 170 kyr was identified in the TOC data, which may reflect the combined effects of obliquity and other orbital parameters.DiscussionSpectral analysis of paleoenvironmental indicators showed that long eccentricity cycle had varying degrees of influence on changes in paleoclimate, paleosalinity, and paleoredox conditions. Additionally, a 1.2 Myr cycle was identified as a significant factor influencing sea level changes during the early Pleistocene in the South China Sea (SCS). In addition, it is confirmed that the dominant period of the glacial-interglacial cycle in the SCS from 0.6 Ma to the present is 100 kyr period. Synthesize the above analysis, during phases of low amplitude in the 405 kyr cycle or minimum value of the 100 kyr cycle, which are associated with lower temperature, conditions become more conducive to hydrate accumulation