Differing interpretations of geophysical and geologic data have led to debate regarding continent... more Differing interpretations of geophysical and geologic data have led to debate regarding continent-scale plate configuration, subduction polarity, and timing of collisional events on the western North American plate margin in pre–mid-Cretaceous time. One set of models involves collision and accretion of far-traveled “exotic” terranes against the continental margin along a west-dipping subduction zone, whereas a second set of models involves long-lived, east-dipping subduction under the continental margin and a fringing or “endemic” origin for many Mesozoic terranes on the western North American plate margin. Here, we present new detrital zircon U-Pb ages from clastic rocks of the Rattlesnake Creek and Western Klamath terranes in the Klamath Mountains of northern California and southern Oregon that provide a test of these contrasting models. Our data show that portions of the Rattlesnake Creek terrane cover sequence (Salt Creek assemblage) are no older than ca. 170–161 Ma (Middle–earl...
In the United Arab Emirates (UAE) and Oman, an arid climate coupled with rising populations have ... more In the United Arab Emirates (UAE) and Oman, an arid climate coupled with rising populations have placed increased demand on scarce water resources. This study performs groundwater prospecting in the northern UAE and Oman by delineating Groundwater Potential (GWP), the relative likelihood of a location to accumulate groundwater, by modelling the inVuence of physiographic variables affecting groundwater accumulation. Remote sensing data from ASTER, Landsat-8, Shuttle Radar Topography Mission (SRTM), and Tropical Rainfall Measuring Mission (TRMM) were used to map relevant physiographic variables including elevation, slope, curvature, drainage density, Topographic Wetness Index, lithology/land cover, lineament density, rainfall, and groundwater-induced cool thermal anomaly frequency (GW CTA). Three different techniques were used for the GWP model including Simple Additive Weight (SAW), Probabilistic Frequency Ratios (PFR), and the Analytical Hierarchy Process (AHP). The three derived GWP maps were assessed through validation by comparing the locations of 645 water wells, 49 natural springs, and Ueld observations of groundwater features to GWP zones. The SAW and AHP maps were deemed valid with agreement to moderate or greater potential zones for wells at 98% and 92% and springs at 63% and 86% respectively, and all Ueld observation locations for both maps. Based on the SAW and AHP maps, the highest GWP is located in the Dubai/Sharjah emirates due to optimal runoW accumulation , inUltration conditions, and subsurface storage capacity. Findings of this study demonstrate integration of remote sensing data with the adopted geospatial techniques is a practical method of groundwater prospecting in similarly data scarce, arid environments.
Sedimentary and volcanic rocks in the Blue Mountains province (BMP) of NE Oregon preserve a recor... more Sedimentary and volcanic rocks in the Blue Mountains province (BMP) of NE Oregon preserve a record of Triassic-Jurassic arc magmatism, mountain building, and basinal response to collisional tectonics. Paleozoic and Mesozoic rocks represent two magmatic arcs (Wallowa and Olds Ferry terranes), an intervening oceanic subduction and accretionary complex (Baker terrane), and a thick sedimentary overlap assemblage known as the "Izee terrane". We divide volcanic and sedimentary rocks into two regionally correlative, unconformity-bounded mega-sequences: (1) MS-1, Late Triassic to Early Jurassic deposits that change upward from older volcaniclastic deposits of the Wallowa and Olds Ferry arcs to marine turbidites, shale, and argillite with chert-clast conglomerates and olistostromes derived from the emergent Baker terrane; and (2) MS-2, Early to early-Late Jurassic marine deposits that overlap older structures and record ~20-40 m.y. of deep crustal subsidence in a large marine basin. Many of the known stratigraphic relationships in the Blue Mtns cannot be explained using the existing model for a long-lived, non-collisional Middle Triassic to Late Jurassic west-facing volcanic arc and forearc basin. We therefore propose a new tectonic model for the BMP that is based on existing data and comparison to modern analogues, consisting of: (1) Late Triassic collision between the Wallowa and Olds Ferry arcs, and related development of flexural basins on both sides of the emergent Baker terrane thrust belt; (2) Early to Middle Jurassic arc-continent collision, which resulted in closure of a wide back-arc basin in the east and growth of a large marine collisional basin in the BMP; and (3) Late Jurassic thrusting, regional shortening, and accretion of the basin and underlying terranes to western North America. This analysis suggests that collisional tectonics may have played a significant role in Triassic-Jurassic plate interactions and lithospheric processes that drove mountain building and basin development in the western U.S. and Canadian Cordillera.
Triassic detritus in the Izee area of the BMP, derived from the Baker terrane, is dominated by Pa... more Triassic detritus in the Izee area of the BMP, derived from the Baker terrane, is dominated by Paleozoic, Late Paleoproterozoic, and Late Archean detrital-zircon grains. This suggests that the Baker terrane is genetically related to other Cordilleran accretionary complexes. Jurassic samples are dominated by Mesozoic detrital ages and also include Neoproterozoic and Mesoproterozoic grains interpreted to reflect southwestern US enrichment of grains from an Appalachian source. Jurassic sediment was derived from (1) orogenic highlands in ...
The Blue Mountains Province (BMP) of northeastern Oregon contains Paleozoic-Mesozoic sedimentary ... more The Blue Mountains Province (BMP) of northeastern Oregon contains Paleozoic-Mesozoic sedimentary and volcanic rocks that formed in a complex convergent-margin setting and later were accreted to the western margin of North America. In this paper we describe a new tectonic model for the BMP that includes: (1) Late Triassic to Early Jurassic Molucca Sea-style collision between the Wallowa and Olds Ferry magmatic arcs, and (2) Early to Late Jurassic collision of previously amalgamated terranes with the North American continent (Papua New Guinea-style terrane-continent collision). This is a significant departure from previous models that interpreted the BMP as the site of non-collisional east-dipping subduction of oceanic crust beneath a west-facing magmatic arc from Late Triassic through Late Jurassic time. Our reinterpretation is based on a synthesis of prior studies that reveals critical provenance links and timespace patterns of deposition and basin migration that were not previously recognized. Comparison of stratigraphic relationships in the BMP with the complex mosaic of active convergent margins in present-day Southeast Asia provides useful insights into plate interactions that may have driven regional crustal deformation and basin evolution in western North America during Triassic and Jurassic time.
Sedimentary and volcanic rocks in the Blue Mountains province (BMP) of NE Oregon preserve a recor... more Sedimentary and volcanic rocks in the Blue Mountains province (BMP) of NE Oregon preserve a record of Triassic-Jurassic arc magmatism, mountain building, and basinal response to collisional tectonics. Paleozoic and Mesozoic rocks represent two magmatic arcs (Wallowa and Olds Ferry terranes), an intervening oceanic subduction and accretionary complex (Baker terrane), and a thick sedimentary overlap assemblage known as the "Izee terrane". We divide volcanic and sedimentary rocks into two regionally correlative, unconformity-bounded mega-sequences: (1) MS-1, Late Triassic to Early Jurassic deposits that change upward from older volcaniclastic deposits of the Wallowa and Olds Ferry arcs to marine turbidites, shale, and argillite with chert-clast conglomerates and olistostromes derived from the emergent Baker terrane; and (2) MS-2, Early to early-Late Jurassic marine deposits that overlap older structures and record ~20-40 m.y. of deep crustal subsidence in a large marine basin. Many of the known stratigraphic relationships in the Blue Mtns cannot be explained using the existing model for a long-lived, non-collisional Middle Triassic to Late Jurassic west-facing volcanic arc and forearc basin. We therefore propose a new tectonic model for the BMP that is based on existing data and comparison to modern analogues, consisting of: (1) Late Triassic collision between the Wallowa and Olds Ferry arcs, and related development of flexural basins on both sides of the emergent Baker terrane thrust belt; (2) Early to Middle Jurassic arc-continent collision, which resulted in closure of a wide back-arc basin in the east and growth of a large marine collisional basin in the BMP; and (3) Late Jurassic thrusting, regional shortening, and accretion of the basin and underlying terranes to western North America. This analysis suggests that collisional tectonics may have played a significant role in Triassic-Jurassic plate interactions and lithospheric processes that drove mountain building and basin development in the western U.S. and Canadian Cordillera.
Differing interpretations of geophysical and geologic data have led to debate regarding continent... more Differing interpretations of geophysical and geologic data have led to debate regarding continent-scale plate configuration, subduction polarity, and timing of collisional events on the western North American plate margin in pre–mid-Cretaceous time. One set of models involves collision and accretion of far-traveled “exotic” terranes against the continental margin along a west-dipping subduction zone, whereas a second set of models involves long-lived, east-dipping subduction under the continental margin and a fringing or “endemic” origin for many Mesozoic terranes on the western North American plate margin. Here, we present new detrital zircon U-Pb ages from clastic rocks of the Rattlesnake Creek and Western Klamath terranes in the Klamath Mountains of northern California and southern Oregon that provide a test of these contrasting models. Our data show that portions of the Rattlesnake Creek terrane cover sequence (Salt Creek assemblage) are no older than ca. 170–161 Ma (Middle–earl...
In the United Arab Emirates (UAE) and Oman, an arid climate coupled with rising populations have ... more In the United Arab Emirates (UAE) and Oman, an arid climate coupled with rising populations have placed increased demand on scarce water resources. This study performs groundwater prospecting in the northern UAE and Oman by delineating Groundwater Potential (GWP), the relative likelihood of a location to accumulate groundwater, by modelling the inVuence of physiographic variables affecting groundwater accumulation. Remote sensing data from ASTER, Landsat-8, Shuttle Radar Topography Mission (SRTM), and Tropical Rainfall Measuring Mission (TRMM) were used to map relevant physiographic variables including elevation, slope, curvature, drainage density, Topographic Wetness Index, lithology/land cover, lineament density, rainfall, and groundwater-induced cool thermal anomaly frequency (GW CTA). Three different techniques were used for the GWP model including Simple Additive Weight (SAW), Probabilistic Frequency Ratios (PFR), and the Analytical Hierarchy Process (AHP). The three derived GWP maps were assessed through validation by comparing the locations of 645 water wells, 49 natural springs, and Ueld observations of groundwater features to GWP zones. The SAW and AHP maps were deemed valid with agreement to moderate or greater potential zones for wells at 98% and 92% and springs at 63% and 86% respectively, and all Ueld observation locations for both maps. Based on the SAW and AHP maps, the highest GWP is located in the Dubai/Sharjah emirates due to optimal runoW accumulation , inUltration conditions, and subsurface storage capacity. Findings of this study demonstrate integration of remote sensing data with the adopted geospatial techniques is a practical method of groundwater prospecting in similarly data scarce, arid environments.
Sedimentary and volcanic rocks in the Blue Mountains province (BMP) of NE Oregon preserve a recor... more Sedimentary and volcanic rocks in the Blue Mountains province (BMP) of NE Oregon preserve a record of Triassic-Jurassic arc magmatism, mountain building, and basinal response to collisional tectonics. Paleozoic and Mesozoic rocks represent two magmatic arcs (Wallowa and Olds Ferry terranes), an intervening oceanic subduction and accretionary complex (Baker terrane), and a thick sedimentary overlap assemblage known as the "Izee terrane". We divide volcanic and sedimentary rocks into two regionally correlative, unconformity-bounded mega-sequences: (1) MS-1, Late Triassic to Early Jurassic deposits that change upward from older volcaniclastic deposits of the Wallowa and Olds Ferry arcs to marine turbidites, shale, and argillite with chert-clast conglomerates and olistostromes derived from the emergent Baker terrane; and (2) MS-2, Early to early-Late Jurassic marine deposits that overlap older structures and record ~20-40 m.y. of deep crustal subsidence in a large marine basin. Many of the known stratigraphic relationships in the Blue Mtns cannot be explained using the existing model for a long-lived, non-collisional Middle Triassic to Late Jurassic west-facing volcanic arc and forearc basin. We therefore propose a new tectonic model for the BMP that is based on existing data and comparison to modern analogues, consisting of: (1) Late Triassic collision between the Wallowa and Olds Ferry arcs, and related development of flexural basins on both sides of the emergent Baker terrane thrust belt; (2) Early to Middle Jurassic arc-continent collision, which resulted in closure of a wide back-arc basin in the east and growth of a large marine collisional basin in the BMP; and (3) Late Jurassic thrusting, regional shortening, and accretion of the basin and underlying terranes to western North America. This analysis suggests that collisional tectonics may have played a significant role in Triassic-Jurassic plate interactions and lithospheric processes that drove mountain building and basin development in the western U.S. and Canadian Cordillera.
Triassic detritus in the Izee area of the BMP, derived from the Baker terrane, is dominated by Pa... more Triassic detritus in the Izee area of the BMP, derived from the Baker terrane, is dominated by Paleozoic, Late Paleoproterozoic, and Late Archean detrital-zircon grains. This suggests that the Baker terrane is genetically related to other Cordilleran accretionary complexes. Jurassic samples are dominated by Mesozoic detrital ages and also include Neoproterozoic and Mesoproterozoic grains interpreted to reflect southwestern US enrichment of grains from an Appalachian source. Jurassic sediment was derived from (1) orogenic highlands in ...
The Blue Mountains Province (BMP) of northeastern Oregon contains Paleozoic-Mesozoic sedimentary ... more The Blue Mountains Province (BMP) of northeastern Oregon contains Paleozoic-Mesozoic sedimentary and volcanic rocks that formed in a complex convergent-margin setting and later were accreted to the western margin of North America. In this paper we describe a new tectonic model for the BMP that includes: (1) Late Triassic to Early Jurassic Molucca Sea-style collision between the Wallowa and Olds Ferry magmatic arcs, and (2) Early to Late Jurassic collision of previously amalgamated terranes with the North American continent (Papua New Guinea-style terrane-continent collision). This is a significant departure from previous models that interpreted the BMP as the site of non-collisional east-dipping subduction of oceanic crust beneath a west-facing magmatic arc from Late Triassic through Late Jurassic time. Our reinterpretation is based on a synthesis of prior studies that reveals critical provenance links and timespace patterns of deposition and basin migration that were not previously recognized. Comparison of stratigraphic relationships in the BMP with the complex mosaic of active convergent margins in present-day Southeast Asia provides useful insights into plate interactions that may have driven regional crustal deformation and basin evolution in western North America during Triassic and Jurassic time.
Sedimentary and volcanic rocks in the Blue Mountains province (BMP) of NE Oregon preserve a recor... more Sedimentary and volcanic rocks in the Blue Mountains province (BMP) of NE Oregon preserve a record of Triassic-Jurassic arc magmatism, mountain building, and basinal response to collisional tectonics. Paleozoic and Mesozoic rocks represent two magmatic arcs (Wallowa and Olds Ferry terranes), an intervening oceanic subduction and accretionary complex (Baker terrane), and a thick sedimentary overlap assemblage known as the "Izee terrane". We divide volcanic and sedimentary rocks into two regionally correlative, unconformity-bounded mega-sequences: (1) MS-1, Late Triassic to Early Jurassic deposits that change upward from older volcaniclastic deposits of the Wallowa and Olds Ferry arcs to marine turbidites, shale, and argillite with chert-clast conglomerates and olistostromes derived from the emergent Baker terrane; and (2) MS-2, Early to early-Late Jurassic marine deposits that overlap older structures and record ~20-40 m.y. of deep crustal subsidence in a large marine basin. Many of the known stratigraphic relationships in the Blue Mtns cannot be explained using the existing model for a long-lived, non-collisional Middle Triassic to Late Jurassic west-facing volcanic arc and forearc basin. We therefore propose a new tectonic model for the BMP that is based on existing data and comparison to modern analogues, consisting of: (1) Late Triassic collision between the Wallowa and Olds Ferry arcs, and related development of flexural basins on both sides of the emergent Baker terrane thrust belt; (2) Early to Middle Jurassic arc-continent collision, which resulted in closure of a wide back-arc basin in the east and growth of a large marine collisional basin in the BMP; and (3) Late Jurassic thrusting, regional shortening, and accretion of the basin and underlying terranes to western North America. This analysis suggests that collisional tectonics may have played a significant role in Triassic-Jurassic plate interactions and lithospheric processes that drove mountain building and basin development in the western U.S. and Canadian Cordillera.
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Papers by Todd LaMaskin