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Showing 1 to 20 of 159 for “"Proterozoic"”.
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Cyanobacterial evolution and interactions with the Proterozoic world
… well-preserved microbial fossils from the Proterozoic (2500 to 540 million years ago). Some of these exceptional fossils are identifiable as cyanobacteria that were preserved by pyrite, amorphous silica (SiO₂) and other minerals. Although a record exists of these organisms, the sparse …
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Re-Os geochronology and geochemistry of Proterozoic sedimentary successions
… This thesis presents new geochronology data from Proterozoic sedimentary successions and insights into Re-Os systematics of organic-rich sedimentary rocks and petroleum products such as bitumen and oil. New Re-Os ORS geochronology from two drill cores indicate that the Proterozoic Atar Group of …
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Metamorphic and crustal evolution of Australian-Antarctic Proterozoic margins
… and thermally extreme conditions during the Mesoproterozoic (D1/M1: 1345–1260 Ma; D2/M2: 1220–1130 Ma). Occurring along the margins of the Australian and East Antarctic Archean–Paleoproterozoic cratons, this system is geographically and geodynamically central to models for the Proterozoic …
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Contributions to the Proterozoic and Cambrian Evolution of Eukaryotes
… contributions to improve our understanding of Proterozoic-Cambrian evolution of eukaryote life. Chapter 1 provides, for the first time, a quantitative characterization of the evolutionary trends of Proterozoic macroalgae. The analysis reveals that morphological disparity of Paleoproterozoic …
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Biogeochemical and phylogenetic signals of Proterozoic and Phanerozoic microbial metabolisms
… chitinase homologs via HGT during the late Neoproterozoic into the early Paleozoic. These results also show that, following these HGT events, recipient terrestrial bacterial clades diversified ∼400-500 Ma, consistent with established timescales of arthropod and plant terrestrialization. …
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Proterozoic structures in north-central North Dakota: a gravity study
<p> The purpose of this study was to determine the structure of the contact between the Superior Craton and the Trans-Hudson orogenic belt in north-central North Dakota between latitude 48 and 49 degrees north and longitude 100 and 102 degrees west, using gravity modeling. Major structural and …
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Biogeochemical and phylogenetic signals of Proterozoic and Phanerozoic microbial metabolisms
… chitinase homologs via HGT during the late Neoproterozoic into the early Paleozoic. These results also show that, following these HGT events, recipient terrestrial bacterial clades diversified ~400-500 Ma, consistent with established timescales of arthropod and plant terrestrialization. …
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Polyphase Proterozoic tectonometamorphic history of the Taos Range, northern New Mexico
Proterozoic rocks in the Taos Range of northern New Mexico preserve components of a protracted tectonic history involving pre-1.7 Ga, 1.65 Ga, 1.4 Ga, and possible 1.1 Ga tectonism. The southern Taos Range is a 1.76 – 1.7 Ga volcano-plutonic complex with tectonically interlayered remnants of the …
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Geochemistry and petrogenesis of the Proterozoic Pater metavolcanic suite, Spragge, Ontario /
The Pater metavolcanic suite (PVS) was extruded as part O'f the basal Pater Formation of the Huronian Supergroup ca. 2.4 Ga. They Ars classified as wi thin-plate tholeiites associated with an immature ri-fting episode, and are inter layered with associated vol cani clastic and metasedimentary …
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Earliest Cambrian - latest Proterozoic ichnofossils and problematic fossils from Inyo County, California
… fossils was made from Lower Cambrian to Upper Proterozoic (<em>sensu</em> Cloud, 1973) strata of Inyo County, California. Specimens were collected from the Wyman, Reed, Deep Spring, and Campito Formations in the White-Inyo Mountains and compared to material from the correlated Stirling and Wood …
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Early proterozoic (1.9 Ga) thrombolites of the Rocknest formation, Northwest Territories, Canada
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1990.
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Evolution of continental crust in the Proterozoic : growth and reworking in orogenic systems
… has been used on three different Palaeo- to Meso-Proterozoic orogenic belts; in Fennoscandia, in North American Grenville and in the Birimian terrane of the West African craton. The eastern part of the Sveconorwegian Province, located in the southwestern part of the Fennoscandian Shield, is made …
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Petrology of early Proterozoic granitoids in the Halls Creek mobile zone, northern Australia
Errata pasted onto front end paper.
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Metamorphism and Deformation in Early Proterozoic Basic Dykes Near Scourie, Northwest Scotland (Amphibolite)
Early Proterozoic amphibolite dykes of the Scourie Dyke swarm, exposed in the transitional Archean to Proterozoic Lewisian basement near Scourie, Northwest Scotland, exhibit complex morphologies, mineralogies, and microfabrics. Dyke morphology is often highly variable, and was controlled to a large …
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A sedimentological and structural analysis of the Proterozoic Uncompahgre Group, Needle Mountains, Colorado
Siliciclastic sediments of the Proterozoic Uncompahgre Group can be subdivided into stratigraphic units of quartzite (Q) and pelite (P); these units include a basal, fining- and thinning-upward retrogradational sequence (Q1-P1) that records the transition from an alluvial to a shallow-marine …
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The role of the Picuris orogeny in the tectonic evolution of Proterozoic North America
… on the growth of North America during the Proterozoic. Researchers have debated the role of three orogenies in shaping the southwestern margin of North America: the ∼1.80-1.60 Ga Yavapai and Mazatzal orogenies, and the newly recognized ∼1.40 Ga Picuris orogeny. We address this question at …
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Evolution of early Proterozoic passive-margin carbonate platform, Rocknest Formation, Wopmay Orogen, N.W.T., Canada
… Wopmay Oroqen, N.W.T., Canada, is an early Proterozoic (l.B9 Ga) passivemargin carbonate platform. It is an eastward-thinning prism, 0 to 1,100 m thick, extending for over 220 km parallel to strike, and over 200 k.m perpendicular to strike. It contains from west to east, slope, outer-shelf, …
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History and timing of polyphase Proterozoic deformation in the Manzano thrust belt, central New Mexico
… Rift, provide spectacular exposures of the Proterozoic Manzano thrust belt. This region is an important place to better characterize polyphase deformation and magmatism related to the assembly of Laurentia, particular the 1.65-1.60 Ga Mazatzal orogeny and the later 1.4 Ga thermo-tectonic …
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