Abstract:The Cambrian Maotianshan Shale in Yunnan Province, China contains the well-preserved soft-body fossils of the Chengjiang Biota. The high quality preservation of the non-mineralizing biota (soft tissues and whole carcasses) shows regional and temporal differences, suggesting that paleogeography and local environmental conditions might have contributed to the taphonomy of these fossils. In this paper we present new results from petrographic, geochemical and detrital zircon analyses, and provide a new interpretat… Show more
“…Abbreviations are: Gr = group; Fm = formation; DST = Doushantuo; CJ = Chengjiang. Data sources for detrital zircon U‐Pb: (a) Kunyang Group (Liu et al, 2020; Sun et al, 2009; Wang et al, 2012), Chengjiang and Doushantuo formations and their equivalents (Wang et al, 2012; X. Zhou et al, 2018) and Shiyantou and Yu'anshan formations (Hofmann et al, 2016; Wang et al, 2012; Yang et al, 2018); (b) E SCB (Wang et al, 2010; K. Wang et al, 2018; Wang, Zeng, et al, 2018; Wu et al, 2010; Xu et al, 2013; Yao et al, 2014, 2015), Indochina (Kang et al, 2019; Wang et al, 2016; Zhao et al, 2017), Australia (Martin et al, 2017 and references therein; Yao et al, 2018), Himalaya (Gehrels et al, 2011; Martin et al, 2005; Myrow et al, 2010, 2016; Yin et al, 2010), and Iran (Etemad‐Saeed et al, 2016; Honarmand et al, 2016; Horton et al, 2008).…”
Section: Resultsmentioning
confidence: 99%
“…(b) Geological map of the study area and sample locations for both this study and previous studies (adapted from 1:500,000 map of Yunnan Province on the National Geological Archives of China, http://en.ngac.org.cn/). (c) Integrated Ediacaran‐Cambrian transitional succession of the eastern Yunnan Province, with samples collected for detrital zircon analyses by Hofmann et al (2016), Yang et al (2018), and this study. Number in the bracket following the sample name indicates the sampling location shown in Figure 1b.…”
Section: Geological Background and Samplingmentioning
The South China Block (SCB) has been regarded by many as an integral part of Gondwana, but proposed timing and processes for its accretion to Gondwana vary and remain contentious, largely owing to the lack of reliable Pan-African age paleomagnetic data and tectono-magmatic records from the SCB. Integrated in situ U-Pb ages and Hf-O isotope analyses of detrital zircons from geochronologically well-calibrated Ediacaran-Cambrian sedimentary rocks of western SCB reveal age populations of 2.51, 1.85, 1.20, 0.80, and 0.52 Ga. Detrital zircon age spectra indicate a major tectonic transition for the SCB during 0.56-0.54 Ga, interpreted to reflect the beginning of the collision between SCB-Indochina and NW India blocks. The collisional event lasted until early Ordovician, leading to the suturing of the SCB-Indochina to the northern margin of East Gondwana. Plain Language Summary The South China Block is thought to be a part of the Gondwana superterrane, which was composed of more than half of all continents 650-400 million years ago (Ma). However, questions of when and how the South China Block collided with Gondwana are yet to be answered. In this study, we conducted provenance analyses of sedimentary rocks whose depositional ages were known via radioisotopic dating and chemo-biostratigraphy in the western South China Block. The results reveal a change in tectonic setting of the South China Block at 560-540 Ma, interpreted as the onset of the collision between the South China Block and India along the northern margin of East Gondwana.
“…Abbreviations are: Gr = group; Fm = formation; DST = Doushantuo; CJ = Chengjiang. Data sources for detrital zircon U‐Pb: (a) Kunyang Group (Liu et al, 2020; Sun et al, 2009; Wang et al, 2012), Chengjiang and Doushantuo formations and their equivalents (Wang et al, 2012; X. Zhou et al, 2018) and Shiyantou and Yu'anshan formations (Hofmann et al, 2016; Wang et al, 2012; Yang et al, 2018); (b) E SCB (Wang et al, 2010; K. Wang et al, 2018; Wang, Zeng, et al, 2018; Wu et al, 2010; Xu et al, 2013; Yao et al, 2014, 2015), Indochina (Kang et al, 2019; Wang et al, 2016; Zhao et al, 2017), Australia (Martin et al, 2017 and references therein; Yao et al, 2018), Himalaya (Gehrels et al, 2011; Martin et al, 2005; Myrow et al, 2010, 2016; Yin et al, 2010), and Iran (Etemad‐Saeed et al, 2016; Honarmand et al, 2016; Horton et al, 2008).…”
Section: Resultsmentioning
confidence: 99%
“…(b) Geological map of the study area and sample locations for both this study and previous studies (adapted from 1:500,000 map of Yunnan Province on the National Geological Archives of China, http://en.ngac.org.cn/). (c) Integrated Ediacaran‐Cambrian transitional succession of the eastern Yunnan Province, with samples collected for detrital zircon analyses by Hofmann et al (2016), Yang et al (2018), and this study. Number in the bracket following the sample name indicates the sampling location shown in Figure 1b.…”
Section: Geological Background and Samplingmentioning
The South China Block (SCB) has been regarded by many as an integral part of Gondwana, but proposed timing and processes for its accretion to Gondwana vary and remain contentious, largely owing to the lack of reliable Pan-African age paleomagnetic data and tectono-magmatic records from the SCB. Integrated in situ U-Pb ages and Hf-O isotope analyses of detrital zircons from geochronologically well-calibrated Ediacaran-Cambrian sedimentary rocks of western SCB reveal age populations of 2.51, 1.85, 1.20, 0.80, and 0.52 Ga. Detrital zircon age spectra indicate a major tectonic transition for the SCB during 0.56-0.54 Ga, interpreted to reflect the beginning of the collision between SCB-Indochina and NW India blocks. The collisional event lasted until early Ordovician, leading to the suturing of the SCB-Indochina to the northern margin of East Gondwana. Plain Language Summary The South China Block is thought to be a part of the Gondwana superterrane, which was composed of more than half of all continents 650-400 million years ago (Ma). However, questions of when and how the South China Block collided with Gondwana are yet to be answered. In this study, we conducted provenance analyses of sedimentary rocks whose depositional ages were known via radioisotopic dating and chemo-biostratigraphy in the western South China Block. The results reveal a change in tectonic setting of the South China Block at 560-540 Ma, interpreted as the onset of the collision between the South China Block and India along the northern margin of East Gondwana.
“…1 ). We use the timescale for this interval from available radiometric dates from fossiliferous strata of Siberia, South China, and Avalonia 93 – 101 (see Supplementary data).…”
Section: Methods and Datamentioning
confidence: 99%
“… Figure 1 Early Cambrian time scale for the Siberian Platform, Russia, with key radiometric dates (numbered; Siberian radiometric dates are in bold), international chronostratigraphy (ICS), and stages and zones accepted for the Siberian Platform. Radiometric dates from 1 27 , 93 ; 2 94 ; 3 95 , 4 96 ; 5 97 ; 6 98 – 100 ; 7 30 ; 8 101 . Right column shows numbered temporal units, each c. 2.5 Myr in duration.…”
The dynamics of how metazoan phyla appeared and evolved – known as the Cambrian Explosion – remains elusive. We present a quantitative analysis of the temporal distribution (based on occurrence data of fossil species sampled in each time interval) of lophotrochozoan skeletal species (n = 430) from the terminal Ediacaran to Cambrian Stage 5 (~545 – ~505 Million years ago (Ma)) of the Siberian Platform, Russia. We use morphological traits to distinguish between stem and crown groups. Possible skeletal stem group lophophorates, brachiopods, and molluscs (n = 354) appear in the terminal Ediacaran (~542 Ma) and diversify during the early Cambrian Terreneuvian and again in Stage 2, but were devastated during the early Cambrian Stage 4 Sinsk extinction event (~513 Ma) never to recover previous diversity. Inferred crown group brachiopod and mollusc species (n = 76) do not appear until the Fortunian, ~537 Ma, radiate in the early Cambrian Stage 3 (~522 Ma), and with minimal loss of diversity at the Sinsk Event, continued to diversify into the Ordovician. The Sinsk Event also removed other probable stem groups, such as archaeocyath sponges. Notably, this diversification starts before, and extends across the Ediacaran/Cambrian boundary and the Basal Cambrian Carbon Isotope Excursion (BACE) interval (~541 to ~540 Ma), ascribed to a possible global perturbation of the carbon cycle. We therefore propose two phases of the Cambrian Explosion separated by the Sinsk extinction event, the first dominated by stem groups of phyla from the late Ediacaran, ~542 Ma, to early Cambrian stage 4, ~513 Ma, and the second marked by radiating bilaterian crown group species of phyla from ~513 Ma and extending to the Ordovician Radiation.
“…Therefore, such elemental enrichment and depletion can be used as a guide for estimating the intensity of chemical weathering for the siliciclastic source materials (Ghosh & Sarkar, ; Lee, ; Moradi et al, ; Pundaree et al, ). The concentrations of those chemical elements are generally controlled by weathering duration, diagenetic processes, original composition of the parent material, average tectonic uplift of the source region, and climatic variations (Akarish & El‐Gohary, ; Buggle, Glaser, Hambach, Gerasimenko, & Markovic, ; Ghosh & Sarkar, ; Hofmann, Li, Chen, MacKenzie, & Hinman, ; Moosavirad, Janardhana, Sethumadhav, Moghadam, & Shankara, ; Nagarajan et al, ).…”
Upper Cretaceous oil shales accumulated in intracratonic sedimentary basins along the Central Eastern Desert. Comprehensive geochemical analyses have been applied on 3 Maastrichtian oil shale horizons from the Duwi and Dakhla formations (El‐Beida and El‐Nakheil mines). We provide significant clues for chemical weathering, sediment recycling, petrogenesis, and tectonic setting of oil shales' source material. The mineralogical composition of the studied oil shales is generally characterized by carbonates, phyllosilicates, quartz, fluorapatite, and sulphides. The geochemistry is characterized by high Ca, P, Ni, U, and Cr values compared to standard post‐Archean Australian shales (PAAS). Their chondrite‐normalized patterns are distinguished by LREE enrichment, HREE depletion, negative Eu anomaly, and typical shale‐like PAAS‐normalized REE patterns. Furthermore, the total REE content is positively correlated with Si, K, Na, Fe, Al, Ti, and Mn, indicating that the REE of the investigated oil shales originated from terrigenous sources. Diverse proxies (e.g., CIA, CPA, and PIA) and the A–CN–K ternary diagram suppose that the source rock succession of the oil shales experienced moderate to intensive chemical weathering. Various geochemical parameters suggest that the oil shales were predominately derived from intermediate, with a minor contribution from felsic, igneous source rocks without any remarkable recycling signals. The average values of (Gd/Yb)N (1.39), Eu/Eu* (0.76), Th/U (0.29), and discrimination diagrams reveal that the oil shales were derived from Neoproterozoic island arc parent rocks. The geochemical results for oil shale provenance are in accordance with the composition and the palaeotectonic history of the igneous rocks in the Central Eastern Desert of Egypt.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
