Results 21 to 30 of about 2,004 (204)

Latest Ordovician age of the Spinachitina fragilis Chitinozoan Biozone in Baltoscandia [PDF]

Estonian Journal of Earth Sciences, 2023
The global Spinachitina fragilis Chitinozoan Biozone has been considered the lowermost Silurian zone in most publications. S. fragilis was first described from the Ohesaare drill core, Estonia, and utilised as a Baltic regional zonal taxon together with ...
Jaak Nõlvak, Yan Liang, Olle Hints
doaj   +1 more source

Expansion of Reducing Marine Environments During the Ireviken Biogeochemical Event: Evidence From the Altajme Core, Gotland, Sweden

Paleoceanography and Paleoclimatology, Volume 38, Issue 2, February 2023., 2023
Abstract New δ34Spy (pyrite) and δ34SCAS (carbonate‐associated sulfate) across the Llandovery‐Wenlock boundary (∼432 Ma) provide evidence for the expansion of reduced marine environments during the Ireviken Biogeochemical Event. This event consists of a major positive carbon isotope excursion, increased biotic turnover, and other major perturbations ...
Brittany M. Stolfus, Lindsi J. Allman, Seth A. Young, Mikael Calner, Emma R. Hartke, Stephan C. Oborny, Alyssa M. Bancroft, Bradley D. Cramer   +7 more
wiley   +1 more source

Geochemical Records Reveal Protracted and Differential Marine Redox Change Associated With Late Ordovician Climate and Mass Extinctions

AGU Advances, Volume 3, Issue 1, February 2022., 2022
Abstract The Ordovician (Hirnantian; 445 Ma) hosts the second most severe mass extinction in Earth history, coinciding with Gondwanan glaciation and increased geochemical evidence for marine anoxia. It remains unclear whether cooling, expanded oxygen deficiency, or a combination drove the Late Ordovician Mass Extinction (LOME).
Nevin P. Kozik, Benjamin C. Gill, Jeremy D. Owens, Timothy W. Lyons, Seth A. Young   +4 more
wiley   +1 more source

Silurian stratigraphy and graptolite faunas of the Mora 001 and Solberga 1 drill cores, Siljan District, central Sweden

Lethaia, Volume 54, Issue 5, Page 610-630, December 2021., 2021
The Mora 001 and Solberga 1 drill cores provide the best available overview on the early Silurian (Llandovery, Rhuddanian to Telychian) graptolite succession available for the Siljan Ring impact structure of central Sweden. The Solberga 1 succession includes a nearly complete graptolite succession from the Pernerograptus revolutus Biozone (late ...
Jörg Maletz
wiley   +1 more source

Three‐Dimensional Morphology and Connectivity of Organic Pores in Shale from the Wufeng and Longmaxi Formations at the Southeast Sichuan Basin in China

Geofluids, Volume 2021, Issue 1, 2021., 2021
Organic pores play an important role in shale reservoirs. Organic pores occur where shale gas was produced and accumulated. However, there is little scientific understanding of the distribution and connectivity of organic pores. Organic pore types and their structural characteristics were studied using a total organic carbon (TOC), thin section ...
Tao Jiang, Zhijun Jin, Zongquan Hu, Wei Du, Zhongbao Liu, Jianhua Zhao, Kun Zhang   +6 more
wiley   +1 more source

New biostratigraphically important chitinozoans from the Kukruse Regional Stage, Upper Ordovician of Baltoscandia [PDF]

Estonian Journal of Earth Sciences, 2015
Three new chitinozoan species, Conochitina savalaensis, Conochitina viruana and Belonechitina intonsa, are described. All these species are stratigraphically restricted to the Kukruse age (lowermost Sandbian, Laufeldochitina stentor chitinozoan Zone) and
Jaak Nõlvak, Garmen Bauert
doaj   +1 more source

Petrographic Characterization and Maceral Controls on Porosity in Overmature Marine Shales: Examples from Ordovician‐Silurian Shales in China and the U.S.

Geofluids, Volume 2021, Issue 1, 2021., 2021
The pore structure characterization and its controlling factors in overmature shales are keys to understand the shale gas accumulation mechanism. Organic matter in source rocks is a mixture of various macerals that have their own specific evolutionary pathways during thermal maturation. Pores within macerals also evolve following their own path.
Lin Wei, Shasha Sun, Dazhong Dong, Zhensheng Shi, Jia Yin, Shudi Zhang, Maria Mastalerz, Xiong Cheng, Kun Zhang   +8 more
wiley   +1 more source

Upper Sandbian–lower Katian bio- and chemostratigraphy in the Pajevonys-13 core section, Lithuania [PDF]

Estonian Journal of Earth Sciences, 2016
The succession of five formations (Auleliai, Vilučiai, Alvitas, Šakiai, Jakšiai) corresponding to the upper Sandbian and lower Katian in southern Lithuania is dated based on new bio- and chemostratigraphical data from the Pajevonys-13 core section.
Linda Hints, Juozas Paškevičius, Tõnu Martma, Peep Männik, Jaak Nõlvak   +4 more
doaj   +1 more source

Graptolites from Silurian (Llandovery Series) sedimentary deposits attributed to a forearc setting, Co To Formation, Co To archipelago, northeast Vietnam [PDF]

, 2020
Newly collected graptolites from the Co To Formation, Co To archipelago, NE Vietnam, comprise assemblages indicative of two biostratigraphical levels within the lower Silurian, Llandovery Series, Telychian Stage: the co-occurrence of Spirograptus ...
Doan, Hung Dinh, Komatsu, Toshifumi, Nguyen, Hung, Nguyen, Minh Trung, Rushton, Adrian, Saparin, Muhammad Aqqid, Trinh, Ha Thai, Vandenbroucke, Thijs, Williams, Mark, Zalasiewicz, Jan   +9 more
core   +1 more source

Microfossils in the Ordovician erratic boulders from Southwestern Finland [PDF]

Bulletin of the Geological Society of Finland, 1995
Chitinozoans, ostracods and acritarchs found in four glacially transported limestone boulders from the south-western coast of Finland have been studied in order to test the usefulness of these microfossil groups in age determinations. Also rare specimens
J. Nõlvak, T. Meidla, A. Uutela
doaj   +1 more source