ARTICLE | doi:10.20944/preprints202303.0518.v1
Subject: Arts And Humanities, Theater Keywords: Mesoproterozoic; Neoproterozoic; Baltica; Amazonia; detrital zircon; Volyn-Orsha basin
Online: 30 March 2023 (02:53:28 CEST)
We used LA-ICP-MS U-Pb data for detrital zircon to constrain the Maximum Depositional Age (MDA) and provenance of clastic sedimentary rocks of the Volyn-Orsha sedimentary basin, which filled an elongated (~625×250 km) depression in SW Baltica and attained ~900 m in thickness. Eighty-six zircons out of one hundred and three yielded concordant dates, with most of them (86 %) falling in the time interval between 1655 ± 3 and 1044 ± 16 Ma and clustering in two peaks at ca. 1630 and 1230 Ma. The remaining zircons yielded dates older than 1800 Ma. The MDA is defined by a tight group of three zircons with a weighted average age of 1079 ± 8 Ma. This age corresponds to the time of a clockwise ~90° rotation of Baltica and the formation of the Grenvillian – Sveconorwegian – Sunsas orogenic belts. Subsidence was facilitated by the presence of eclogites derived from subducted oceanic crust. The sediments of the Orsha sub-basin in the northeastern part of the basin were derived from the local crystalline basement, whereas the sediments in the Volyn sub-basin, extending to the margin of Baltica, were transported from the orogen between Laurentia, Baltica, and Amazonia.
ARTICLE | doi:10.20944/preprints202211.0025.v1
Subject: Environmental And Earth Sciences, Geophysics And Geology Keywords: Ordos Basin; red sandstone; detrital zircon U-Pb dating; tectonothermal events; origin analysis; Danxia landform area in northern Shaanxi, China
Online: 1 November 2022 (09:16:04 CET)
The Danxia landform area of Jingbian Wave Valley is located in the central part of Ordos Basin. The near-red Danxia landform consisting of sandstone in this area is a new discovery in geological circles at home and abroad, and its depositional age and genesis remain a hot topic of discussion at present. As the material basis for its development, red sandstone is of great importance to the in-depth study on its formation date and origin. The paper explores the origin, tectonic significance and paleogeographic pattern of the red sandstone through field geological investigation and zircon U-Pb dating analysis of the red sandstone of the Luohe Formation. The results show that the original materials of the red sandstone was formed in three main age intervals, 252~456 Ma, 1657~2084 Ma, and 2129~2538 Ma, and regional tectonothermal events in the origin area during the three periods were recorded, among which the events in Mesoproterozoic and Paleoproterozoic periods were the most active. The comparative analysis of zircon U-Pb age spectra shows that for the sediment of red sandstone, the early origin is near-origin and late origin is distant-origin. The main origin areas in the study area are the Xingmeng orogenic belt, the North China massif and the Alashan massif; the vertical section reflects that the origin area has the strongest erosion and transport in the upper deposition period, the smallest erosion and transport in the middle deposition period, and the moderate erosion and transport in the lower deposition period. With origins system dominated by the northern origins and the paleogeographic pattern of multi-period and cyclonic, the area mainly experienced four tectonic movement cycles, such as Wutai, Lvliang, Caledon and Haixi.
ARTICLE | doi:10.20944/preprints202203.0017.v1
Subject: Environmental And Earth Sciences, Geophysics And Geology Keywords: East Asia; Detrital zircon; Large River; Rift Basin
Online: 1 March 2022 (11:07:26 CET)
The forming of large rivers are the integral consequences of the deep earth process and the surface. In contrast to the hot topics for rivers related to orogenic domains, rift-related large rivers are largely ignored especially in deep time studies. The Cenozoic East Asia margin provides very good opportunity to observe this kind of rivers. It has been believed that basin-and-swell physiography dominated the East Asia margin and impeded the forming of large rives in the early Cenozoic. In this paper, we combined provenance analysis of East China Sea Basin, where is a crucial place to trace the river evolution in East Asia margin, and regional geologic constraints to reveal drainage reorganizations. Detrital zircon U-Pb ages from the Early Eocene sediments of the East China Sea Basin are firstly reported. Our results together with literature data demonstrate that regional provenance changes occurred at the middle Eocene from one singe age peak at ~110 Ma of proximal sources to multiple age spectrum derived from far inland. Source to sink analysis indicated that the North China Block and Korea Peninsular provided the most detritus. Sedimentation and tectonic features of rift basins in the potential source areas indicated that rivers flowed into Bohai Basin and Jianghan Basin cannot provide terrigenous clasts for the lower reaches in the Eocene. Contrastingly, the dominantly fluvial sediments across the Subei-South Yellow Sea Basin suggested external river system and a bypassing region since the middle Eocene, coinciding with provenance change in ECSB. All these demonstrated that a large river (East Asia River) established in east Asia margin in the middle Eocene and flowed southwestward approximately 1500km to the sea in southern ECSB. This river might last to the middle Miocene. The deep earth processes driven by Izanagi-Pacific ridge subduction resulted in the overfilled stage of Subei-South Yellow Sea Basin and the post-rift subsidence in west depression of ECSB, and thus facilitated the initiation of the EAR. Our finding shed new light on the evolving landscape in East Asia and showed how subduction of deep earth process controlled the initiation of rift-related large rivers.
ARTICLE | doi:10.20944/preprints202111.0477.v1
Subject: Environmental And Earth Sciences, Geophysics And Geology Keywords: Cycladic Blueschist Unit; detrital zircon U-Pb dating; central Cyclades; Provenance
Online: 25 November 2021 (13:27:50 CET)
Detailed mapping and structural observations on the Cycladic Blueschist Unit (CBU) of Iraklia island integrated by detrital zircon (DZ) U-Pb ages elucidate the Mesozoic pre-subduction evolution and the Cenozoic orogenic events. Field data reveal that the Iraklia tectonostratigraphy includes a heterogeneous Lower Schist Unit juxtaposed against a Variegated Marble Unit and an overlying Upper Schist Unit. The contact is an extensional ductile-to-brittle-ductile, top-to-N shear zone, associated with the Oligo-Miocene exhumation. The DZ spectrum of the Lower Schist Unit characterized by Gondwanan/peri-Gondwanan provenance signatures points to Late Triassic maximum depositional ages (MDAs). A quartz-rich schist layer yielded Precambrian DZ ages exclusively, considered part of the pre-Variscan metasedimentary Cycladic Basement, equivalent to those observed on Ios island. A significant change occurred during the deposition of the Upper Schist Unit, revealing Late Cretaceous MDAs and a high amount of Late Paleozoic DZ ages, attesting to more internal Pelagonian source areas. The imprint of Paleotethyan vs. Neotethyan geodynamic events is revealed in the DZ U-Pb ages record. The Triassic DZ input demonstrates eroded volcanic material related to the final Paleotethys closure and the Pindos/CBU rift basin opening. Late Cretaceous metamorphic/magmatic zircons and ~48-56 Ma zircon rims constrain the onset of subduction and high-pressure metamorphism.
REVIEW | doi:10.20944/preprints201911.0093.v1
Subject: Biology And Life Sciences, Insect Science Keywords: microarthropods; decomposition; nutrient mineralization; multi-channel feeding; predation; alternate prey; detrital shunting
Online: 8 November 2019 (10:39:16 CET)
Two desirable functions of healthy soil are nutrient cycling and pest suppression. We review recent literature on the contributions of soil microarthropods to soil health through their intersecting roles in decomposition and nutrient cycling and direct and indirect suppression of plant pests. Microarthropods can impact soil and plant health directly by feeding on pest organisms or serving as alternate prey for larger predatory arthropods, and indirectly, by mediating the ability of crop plants to resist or tolerate insect pests and diseases through interactions with the decomposition food web in support of plant nutrition. Soil fauna, including microarthropods, are key regulators of decomposition at local scales but their role at larger scales is unresolved. Future research priorities include the incorporation of multi-channel omnivory into food web modeling and understanding the vulnerability of our soil carbon to increased global temperatures.