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Articles 1 - 4 of 4
Full-Text Articles in Tectonics and Structure
Exploring Mesoproterozoic Marine Redox States In A Young Banded Iron Formation From The Needle Mountains, Jaya Sharma, Brenhin Keller
Exploring Mesoproterozoic Marine Redox States In A Young Banded Iron Formation From The Needle Mountains, Jaya Sharma, Brenhin Keller
Wetterhahn Science Symposium Posters
Banded iron formations (BIF), as redox-dependent chemical sedimentary rocks, have served as proxies for marine and atmospheric oxygen and iron conditions throughout Earth history. While abundant in the Archean and early Proterozoic, the widespread deposition of BIFs declined following the Great Oxidation Event, as oxygenated surface waters prevented the accumulation of ferrous iron. However, the Needle Mountains, located in southwestern Colorado, houses an anomalously young BIFs deposited between 1.786±10 - 1.801±6 Ga given existing geochronology. Here, we use rare earth element (REE) systematics, bulk chemistry, and petrographic analysis to determine the depositional conditions under which this BIF was formed. We …
Proterozoic To Paleozoic Bedrock Geology Of The Islesboro Block, Penobscot Bay Maine, Usa, Luis Angel Torres
Proterozoic To Paleozoic Bedrock Geology Of The Islesboro Block, Penobscot Bay Maine, Usa, Luis Angel Torres
Dartmouth College Master’s Theses
The Islesboro block is a fault-bounded crustal fragment isolated between the St. Croix and Ellsworth terranes in Penobscot Bay, Maine. We present the results of new geological mapping of the Islesboro 7.5´ quadrangle, which is coupled with new laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) U-Pb zircon data to support revised unit subdivisions and provide an assessment of the age and provenance of the Islesboro block. Based on these data, the Islesboro block consists of: (1) the Paleoproterozoic–Mesoproterozoic(?) Seven Hundred Acre Island Formation, composed of marble, quartzite, and garnet-mica schist, and intruded by highly retrogressed Neoproterozoic (ca. 670–655 Ma) amphibolite …
Tectonic Evolution Of The Northern Margin Of North America, Karol Faehnrich
Tectonic Evolution Of The Northern Margin Of North America, Karol Faehnrich
Dartmouth College Ph.D Dissertations
The northern margin of North America records a protracted history of Neoproterozoic–early Paleozoic rifting and passive margin development, followed by the middle Paleozoic accretion of continental fragments. Contrasting tectonic models have been proposed for the history of continent separation, the role of strike-slip displacement during terrane accretion, and the Mesozoic opening of the Arctic Ocean. Here, I explore several of these models by investigating Neoproterozoic–early Paleozoic sedimentary and volcanic rocks across the northern margin of North American, as well as the main faulted boundaries between displaced terranes and autochthonous rocks of North America. First, I present a new tectonic model …
Timescales Of Magma Transport In The Columbia River Flood Basalts, Determined By Paleomagnetic Data, Joseph Biasi, Leif Karlstrom
Timescales Of Magma Transport In The Columbia River Flood Basalts, Determined By Paleomagnetic Data, Joseph Biasi, Leif Karlstrom
Other Staff Materials
Flood basalts represent major events in Earth History, in part because they are linked to large climate perturbations and mass extinctions. However, the durations of individual flood basalt eruptions, which directly impact potential environmental crises, are poorly constrained. Here we use a combination of paleomagnetic data and thermal modeling to create a magnetic geothermometer (MGT) that can constrain the active transport lifetime of magmatic conduits and intrusions. We apply the MGT technique to eight feeder dike segments of the Columbia River basalts (CRB), demonstrating that some dike segments were actively heating host rocks for less than one month, while other …