Charophytes from the Lower Cretaceous Xiagou Formation in the Jiuquan Basin (northwestern China) and their palaeogeographical significance

Li, Sha; Wang, Qifei; Zhang, Haichun

doi:10.1016/j.cretres.2018.08.010

Cited by 12 publications

(7 citation statements)

References 34 publications

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“…The entire basin area is approximately 2:2 × 10 4 km 2 . Jiuquan Basin is divided into two depressions by the Jiayuguan Uplift [28,29]; the east to west basin area is divided into two depressions of Jiudong and Jiuxi. The area of the Jiudong depression measures 1:1 × 10 4 km 2 , whereas the Jiuxi depression features a smaller area of 0:68 × 10 4 km 2 and the three mainly sedimentary developed sags of Qingxi, Shida, and Huahai [30,31] (Figure 1).…”

Section: Geologic Settingmentioning

confidence: 99%

Pore Structure Characteristics of Tight Carbonate Reservoir in Qingxi Sag, Jiuquan Basin

et al. 2021

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The Xiagou Formation is the main tight oil reservoir in Qingxi Sag of Jiuquan Basin. Given the poor physical properties and other factors restricting tight oil exploitation and production in this area, studies should focus on microscopic pore structure characteristics. In this study, a nano-CT scanner, a SEM, and an NMR were used to study the pore structure characteristics of a tight carbonate reservoir in Qingxi Sag, Jiuquan Basin. The Xiagou Formation reservoir mainly consists of gray argillaceous dolomite and dolomitic mudstone. The pore categories are mainly elliptic, irregular, intergranular, and intragranular and mostly filled with clay and carbonate cement. Pore space is small, the intergranular or organic pores are mostly separated, and pore-throat is weakly connected. The throats mostly develop with lamellar and tube bundle-like characteristics and with poor seepage ability. The pore-throats mostly span from nanometer to micrometer sizes, and pore diameters are mainly concentrated in the range of 0.01–0.1 and 1–10 μm. It is a unimodal pattern mainly composed of micropores, or a bimodal regular allocation dominated by micropores supplemented by macropores. The relationship between micropore (<0.1 μm) and macropore (>1 μm) content allocation and mean pore diameter strongly controls the permeability of reservoir rocks. When macropore content reaches more than 85%, or when pore content totals less than 3%, the permeability of a reservoir remarkably increases. At a higher ratio of the average finest throat sectional area and throat-pore of reservoir rock, the throat radius lies closer to the connecting pore radius, pore and throat connectivity improves, and reservoir seepage ability becomes stronger. Based on reservoir capacity and seepage ability, pore structures of the tight carbonate reservoirs in study area are classified into type I (small-pore–thin-throat), type II (thin-pore–thin-throat), and type III (microporous-microthroat) with rock permeability>0.1 mD, 0.05–0.1 mD, and <0.05 mD, respectively. The type I pore structure reservoir should be regarded as an indicator of tight oil “sweet spots” reservoir in the study area.

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Section: Geologic Settingmentioning

confidence: 99%

Pore Structure Characteristics of Tight Carbonate Reservoir in Qingxi Sag, Jiuquan Basin

et al. 2021

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“…The ostracod fauna from the Tsagaan Tsuvarga Section consists of three species of three genera. Among them, Yumenia oriformis was reported from the Lower Huihuipu Series (Hou, 1958), which is equal to the Xiagou Formation of China and known as early Aptian in age (Xi et al, 2019; Li et al, 2020). Scabriculocypris subscalara was found in the Barremian Nantun Formation of the Hailaer Basin, China (Ye et al, 2003; Xi et al, 2019).…”

Section: Discussionmentioning

confidence: 99%

Nonmarine ostracod fauna from the Lower Cretaceous Shinekhudag Formation (southwest Mongolia): taxonomy, biostratigraphy, and paleoecology

Choi

Wang²

2023

J. Paleontol.

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This work provides the detailed investigation (taxonomy, biostratigraphy, and paleoecology) of a nonmarine ostracod fauna from the Shinekhudag Formation in Gobi–Altai area, southwest Mongolia. The samples from two sections (Tsagaan Tsuvarga and Oshih Hollow East) yielded various ostracods assigned to nine species belonging to six genera: Cypridea verrucata Neustrueva, 1974, C. ihsienensis Hou, 1958, C. unicostata Galeeva, 1955, C. tumefacta Neustrueva, 1974, Yumenia cf. Y. oriformis Hou, 1958, Scabriculocypris subscalara Zhang and Chen in Ye et al., 2003, ?Trapezoidella sp., Candona sp., and Vlakomia ulanense Neustrueva, 1977. The biostratigraphic application of our taxonomic results suggests that the age of the Shinekhudag Formation is Barremian–Aptian. In addition, the ostracod fauna shows strong affinities to faunas from northeast China and potentially northwest China, providing evidence of faunal exchanges between these regions and southwest Mongolia. The new discovery of Vlakomia ulanense indicates that mid-Cretaceous (Albian) species in northeast China probably originated in Mongolia at the time of deposition of the Shinekhudag Formation. Two ostracod assemblages in the studied sections reflect that different paleoenvironment settings have existed during deposition; the Tsagaan Tsuvarga Section represents a shallow-littoral zone of athalassic (inland) saline lake under arid climate, and the dominance of cypridoideans of the Oshih Hollow East Section is indicative of ephemeral water bodies.

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“…This species was previously used as an index species to characterise a Hauterivian early Barremian biozone in Chinese basins (Wang and Lu 1982, Peng et al 2003, Yang et al 2008. However, more recent data from the Jiuquan Basin suggest a late Barremian early Aptian (more probably early Aptian) age for this species (Li et al 2020), based on a previous chemostratigraphic ( 13 C and 18 O) study performed by Suárez et al (2013) and through comparisons with the age of C. grovesii var. jiuquanensis given by Martín-Closas et al (2009) in Europe.…”

Section: The Barremian-early Aptian Charophyte Biozonation Revisitedmentioning

confidence: 99%

“…With the exception of C. grovesii var. jiuquanensis (= Clypeator jiuquanensis), which is now considered to date to the late Barremian-early Aptian (also in China according to Li et al 2020), the association described within the Perimneste ancora-Clypeator jiuquanensis biozone has been documented in Europe through the Globator maillardii var. steinhauseri European biozone (see Riveline et al 1996), which dates to the latest Berriasian late Hauterivian.…”

Section: Comparison With Other Barremian Charophyte Biozonationsmentioning

confidence: 99%

Barremian–early Aptian charophyte biostratigraphy revisited

Pérez-Cano¹,

Bover‐Arnal²,

Martı́n-Closas³

2022

nos

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New Barremian early Aptian charophyte biozonations are proposed here based on the charophyte succession in the Maestrat Basin (Iberian Chain, Spain). Biostratigraphic analysis distinguished two biozonations, European and Eurasian, which were compared to establish correlations. This is the first time that Early Cretaceous charophyte biozones are calibrated by means of strontium-isotope stratigraphy, enabling their correlation with the coeval marine realm (ammonite biostratigraphy). The European charophyte biozonation is formed of two partial range biozones, whose index species were endemic from the Cretaceous Tethyan Archipelago (present-day Europe and Northern Africa):(1) Globator maillardii var. trochiliscoides (early Barremian) and (2) Ascidiella cruciata-Pseudoglobator paucibracteatus. The base of the A. cruciata-P. paucibracteatus biozone was calibrated with an oyster shell sample whose 87 Sr/ 86 Sr is 0.707482, translating to a late early Barremian age. The total time span of this latter biozone is late early Barremian early Aptian. The Eurasian biozonation involves a novel Lower 2 Cretaceous charophyte biostratigraphy. It has more resolution than the European biozonation, as it is composed of three partial range biozones whose index species were well-distributed in Eurasia. From oldest to youngest these are: (1) Atopochara trivolvis var. triquetra, (2) Hemiclavator neimongolensis var. neimongolensis, and (3) Clavator grovesii var. jiuquanensis. The A. trivolvis var. triquetra biozone characterises the early Barremian, being almost equivalent to the European G. maillardii var. trochiliscoides biozone. The base of the H. neimongolensis var. neimongolensis biozone is marked by the first appearance datum (FAD) of Hemiclavator neimongolensis var. neimongolensis and was calibrated with an oyster shell whose 87 Sr/ 86 Sr is 0.707481 corresponding to a late early Barremian age. The top of the H. neimongolensis var. neimongolensis biozone coincides with the FAD of Clavator grovesii var. jiuquanensis. The base of the C. grovesii var. jiuquanensis biozone was dated with an oyster sample sample collected 25 m below the FAD of C. grovesii var. jiuquanensis. The 87 Sr/ 86 Sr value of this sample is 0.707489, which translates into an early late Barremian age. Thus, the H. neimongolensis var. neimongolensis biozone spans the late early Barremian-early late Barremian interval. The top of the Clavator grovesii var. jiuquanensis biozone (late Barremian early Aptian) is marked by the FAD of Clavator grovesii var. lusitanicus. The newly proposed Eurasian charophyte biozonation will facilitate the correlation between non-marine basins in one of the largest continental areas on Earth.

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Charophytes from the Lower Cretaceous Xiagou Formation in the Jiuquan Basin (northwestern China) and their palaeogeographical significance

Cited by 12 publications

References 34 publications

Pore Structure Characteristics of Tight Carbonate Reservoir in Qingxi Sag, Jiuquan Basin

Pore Structure Characteristics of Tight Carbonate Reservoir in Qingxi Sag, Jiuquan Basin

Nonmarine ostracod fauna from the Lower Cretaceous Shinekhudag Formation (southwest Mongolia): taxonomy, biostratigraphy, and paleoecology

Barremian–early Aptian charophyte biostratigraphy revisited

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