Results 21 to 30 of about 39,183 (233)

Anomalous negative excursion of carbon isotope in organic carbon after the last Paleoproterozoic glaciation in North America [PDF]

open access: yes, 2010
Early Paleoproterozoic time (2.5–2.0 Ga) spanned a critical phase in Earth's history, characterized by repeated glaciations and an increase in atmospheric oxygen (the Great Oxidation Event (GOE)).
Bekker   +41 more
core   +1 more source

Early Ediacaran collision zone (ca. 620 Ma) in Saudi Arabia and Yemen inferred from aeromagnetic mapping [PDF]

open access: yesLithosphere
The tectonic terranes in the Proterozoic outcrops in Saudi Arabia are separated from those in Yemen by extensive regions that are covered by Phanerozoic sedimentary rocks and Tertiary volcanics.
Moujahed Al-Husseini, Ian C.F. Stewart
doaj   +1 more source

Structural history of the southwestern corner of the Kaapvaal Craton and the adjacent Namaqua realm: new observations and a reappraisal [PDF]

open access: yes, 1991
The rocks along the southwestern margin of the Kaapvaal Craton were deformed up to 7 times during the Early to Middle Proterozoic. The oldest deformation D1 is recorded in the N-S-trending Uitkoms cataclasite of pre-Makganyene age (>2.24 Ga) on the ...
Altermann, Wladyslaw, Hälbich, Ingo W.
core   +1 more source

Enigmatic Mid‐Proterozoic Orogens: Hot, Thin, and Low

open access: yesGeophysical Research Letters, 2021
Since the Archean, secular change in orogenic style is demonstrated through evolution of metamorphic conditions and geochemical proxies. Linked to orogenic style is the amount of crustal thickening and elevation, whereas orogenic vigor is related to the ...
Christopher J. Spencer   +2 more
doaj   +1 more source

Archean versus Phanerozoic oceanic crust formation and tectonics: Ophiolites through time

open access: yesGeosystems and Geoenvironment, 2022
A global compilation of structural, lithological, and geochemical data on a selection of Archean, Proterozoic and Phanerozoic magmatic complexes, interpreted as ophiolites, is presented.
Harald Furnes, Yildirim Dilek
doaj   +1 more source

Provenance and Paleogeography of the 25-17 Ma Rainbow Gardens Formation: Evidence for Tectonic Activity at Ca. 19 Ma and Internal Drainage rather than Throughgoing Paleorivers on the Southwestern Colorado Plateau [PDF]

open access: yes, 2018
The paleogeographic evolution of the Lake Mead region of southern Nevada and northwest Arizona is crucial to understanding the geologic history of the U.S. Southwest, including the evolution of the Colorado Plateau and formation of the Grand Canyon.
Beard, L. Sue   +9 more
core   +2 more sources

The Cambrian Explosion: macroevolution and biomineralization

open access: yesAcademia Biology, 2023
Recent advances in our understanding of the Cambrian evolutionary diversification event (Cambrian Explosion) show that, although eumetazoan stem taxa were present in the late Proterozoic, a tremendous burst of macroevolutionary change occurred near the ...
Mark A. S. McMenamin
doaj   +1 more source

Deep lithospheric dynamics beneath the Sierra Nevada during the Mesozoic and Cenozoic as inferred from xenolith petrology [PDF]

open access: yes, 2001
Peridotite xenoliths erupted in late Miocene basalts (~8 Ma) in the central Sierra Nevada sample a lithosphere that is vertically stratified in terms of age and thermal history.
Brimhall, George H., Jr.   +2 more
core   +1 more source

The laurentian record of neoproterozoic glaciation, tectonism, and eukaryotic evolution in Death Vally, California [PDF]

open access: yes, 2013
Neoproterozoic strata in Death Valley, California contain eukaryotic microfossils and glacial deposits that have been used to assess the severity of putative Snowball Earth events and the biological response to extreme environmental change.
A. E. Fallick   +62 more
core   +1 more source

The early Proterozoic Saari-Kiekki greenstone belt: A representative of the Sariola Group at Kuhmo, Eastern Finland [PDF]

open access: yesBulletin of the Geological Society of Finland, 1989
The early Proterozoic Saari-Kiekki greenstone belt in Kuhmo, eastern Finland, is the deformed remnant of a NW‒SE-trending elongate structural basin c. 15 km long and up to 3 km wide.
E.J. Luukkonen
doaj   +1 more source

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