Friday, February 26th, 2016

Christopher G. Daniel – Jones, James V. III; Daniel, Christopher G.; and Doe, Michael F. “Tectonic and Sedimentary Linkages between the Belt-Purcell Basin and Southwestern Laurentia during the Mesoproterozoic, ca. 1.60-1.40 Ga.” Lithosphere 7, no. 4 (2015) : 465-472.

Christopher G. Daniel, Professor of Geology

Mesoproterozoic sedimentary basins in western North America provide key constraints on pre-Rodinia craton positions and interactions along the western rifted margin of Laurentia. One such basin, the Belt-Purcell basin, extends from southern Idaho into southern British Columbia and contains a >18-km-thick succession of siliciclastic sediment deposited ca. 1.47-1.40 Ga. The ca. 1.47-1.45 Ga lower part of the succession contains abundant distinctive non-Laurentian 1.61-1.50 Ga detrital zircon populations derived from exotic cratonic sources. Contemporaneous metasedimentary successions in the southwestern United States-the Trampas and Yankee Joe basins in Arizona and New Mexico-also contain abundant 1.61-1.50 Ga detrital zircons. Similarities in depositional age and distinctive non-Laurentian detrital zircon populations suggest that both the Belt-Purcell and southwestern U.S. successions record sedimentary and tectonic linkages between western Laurentia and one or more cratons including North Australia, South Australia, and (or) East Antarctica. At ca. 1.45 Ga, both the Belt-Purcell and southwest U.S. successions underwent major sedimentological changes, with a pronounced shift to Laurentian provenance and the disappearance of 1.61-1.50 Ga detrital zircon. Upper Belt-Purcell strata contain strongly unimodal ca. 1.73 Ga detrital zircon age populations that match the detrital zircon signature of Paleoproterozoic metasedimentary rocks of the Yavapai Province to the south and southeast. We propose that the shift at ca. 1.45 Ga records the onset of orogenesis in southern Laurentia coeval with rifting along its northwestern margin. Bedrock uplift associated with orogenesis and widespread, coeval magmatism caused extensive exhumation and erosion of the Yavapai Province ca. 1.45-1.36 Ga, providing a voluminous and areally extensive sediment source-with suitable zircon ages-during upper Belt deposition. This model provides a comprehensive and integrated view of the Mesoproterozoic tectonic evolution of western Laurentia and its position within the supercontinent Columbia as it evolved into Rodinia.

Jones, James V. III; Daniel, Christopher G.; and Doe, Michael F. “Tectonic and Sedimentary Linkages between the Belt-Purcell Basin and Southwestern Laurentia during the Mesoproterozoic, ca. 1.60-1.40 Ga.” Lithosphere 7, no. 4 (2015) : 465-472.

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Friday, February 26th, 2016

Ellen K. Herman – McGuire, Molly M. and Herman, Ellen K. “A Novel ATR-FTIR Technique for Identifying Colloid Composition in Natural Waters.” Hydrological Processes 29, no. 6 (2015) : 1314-1323.

Ellen K. Herman, Associate Professor of Geology

Although understanding colloid composition has been frequently cited as essential to predicting contaminant transport in natural waters, most current methods to collect and identify colloid composition chemically alter the colloids prior to analysis and fail to identify colloid mineralogy and organic components. This paper presents a new, low-cost method employing attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) to identify colloids including organic material in concentrated suspensions. The concentration method employing tangential ultrafiltration at a steady temperature prevents redistribution of dissolved phase and suspended sediments into the colloidal fraction through post-sampling reactions. ATR-FTIR allows for direct analysis of concentrated suspensions rather than requiring drying that may alter composition in the colloidal phase, for example, by precipitating carbonates in samples from karst waters. The ability of this technique to monitor variation in colloidal composition is demonstrated through the examination of colloids under two different flow conditions in a karst aquifer and the West Branch of the Susquehanna River in Central Pennsylvania. Copyright (c) 2014 John Wiley & Sons, Ltd.

McGuire, Molly M. and Herman, Ellen K. “A Novel ATR-FTIR Technique for Identifying Colloid Composition in Natural Waters.” Hydrological Processes 29, no. 6 (2015) : 1314-1323.

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Friday, February 26th, 2016

Carl Kirby – Stewart, Brian W.; Chapman, Elizabeth C.; Capo, Rosemary C.; Johnson, Jason D.; Graney, Joseph R.; Kirby, Carl S.; and Schroeder, Karl T. “Origin of Brines, Salts and Carbonate from Shales of the Marcellus Formation: Evidence from Geochemical and Sr Isotope Study of Sequentially Extracted Fluids.” Applied Geochemistry 60, (2015) : 78-88.

Carl Kirby, Professor of Geology

Fluids co-produced with methane from hydraulically fractured organic-rich shales of the Marcellus Formation (USA) are characterized by high total dissolved solids (TDS), including elevated levels of Ba, Sr and Br. To investigate the source and geologic history of these high-TDS fluids and their dissolved constituents, we carried out a series of sequential extraction experiments on dry-drilled cuttings extracted within, below and above the Marcellus Shale from a well in Tioga County, New York State. The experiments were designed to extract (1) water soluble components, (2) exchangeable cations, (3) carbonate minerals, and (4) hydrochloric acid-soluble constituents. The geochemistry of the resultant leachates highlights the different geochemical reservoirs for extractable elements within the shale; notably, Na and Br were largely water-soluble, while Ba was extracted primarily from exchangeable sites, and Ca and Sr were found both in exchangeable sites and carbonate. Strontium isotope ratios measured on the leachates indicate that each of the element reservoirs has a distinct value. Measured Sr-87/Sr-86 ratios in the water soluble component are similar to those of Marcellus produced water, while the ion exchange reservoir yields lower ratios, and carbonate Sr is lower still, approaching Devonian-Silurian seawater values. Despite the isotopic similarity of water leachates and produced water, the total water chemistry argues against generation of produced water by interaction of hydraulic fracturing fluid with “dry” shale. The high-TDS produced water is most likely trapped formation water (within and/or adjacent to the shale) that is released by hydraulic fracturing. The formation water was affected by multiple processes, possibly including basin scale, tectonically-driven fluid flow. Significant chemical and isotopic differences between Marcellus Shale produced water and overlying Upper Devonian/Lower Mississippian produced waters suggests a hydrologic barrier has been maintained in parts of the Appalachian Basin since the late Paleozoic. (C) 2015 Elsevier Ltd. All rights reserved.

Stewart, Brian W.; Chapman, Elizabeth C.; Capo, Rosemary C.; Johnson, Jason D.; Graney, Joseph R.; Kirby, Carl S.; and Schroeder, Karl T. “Origin of Brines, Salts and Carbonate from Shales of the Marcellus Formation: Evidence from Geochemical and Sr Isotope Study of Sequentially Extracted Fluids.” Applied Geochemistry 60, (2015) : 78-88.

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Friday, February 26th, 2016

Jeffrey M. Trop – Finzel, Emily S.; Ridgway, Kenneth D.; and Trop, Jeffrey M. “Provenance signature of changing plate boundary conditions along a convergent margin: Detrital Record of Spreading-Ridge and Flat-Slab Subduction Processes, Cenozoic Forearc Basins, Alaska.” Geosphere 11, no. 3 (2015) : 823-849.

Jeffrey M. Trop, Professor of Geology

Cenozoic strata from forearc basins in southern Alaska record deposition related to two different types of shallow subduction: Paleocene-Eocene spreading-ridge subduction and Oligocene-Recent oceanic plateau subduction. We use detrital zircon geochronology (n = 1368) and clast composition of conglomerate (n = 1068) to reconstruct the upper plate response to these two subduction events as recorded in forearc basin strata and modern river sediment. Following spreading-ridge subduction, the presence of Precambrian and Paleozoic detrital zircon ages in middle Eocene-lower Miocene arc-margin strata and Early Cretaceous ages in lower Miocene accretionary prism-margin strata indicates that sediment was transported to the basin from older terranes in interior Alaska and from the exhumed eastern part of the Cretaceous forearc system, respectively. By middle-late Miocene time, diminished abundances of these populations reflect shallow subduction of an oceanic plateau and associated exhumation that resulted in an overall contraction of the catchment area for the forearc depositional system.

In the southern Alaska forearc basin system, upper plate processes associated with subduction of a spreading ridge resulted in an abrupt increase in the diversity of detrital zircon ages that reflect new sediment sources from far inboard regions. The detrital zircon signatures from strata deposited during oceanic plateau subduction record exhumation of the region above the flat slab, with the youngest detrital zircon population reflecting the last period of major arc activity prior to insertion of the flat slab. This study provides a foundation for new tectonic and provenance models of forearc basins that have been modified by shallow subduction processes, and may help to facilitate the use of U-Pb dating of detrital zircons to better understand basins that formed under changing geodynamic plate boundary conditions.

Finzel, Emily S.; Ridgway, Kenneth D.; and Trop, Jeffrey M. “Provenance signature of changing plate boundary conditions along a convergent margin: Detrital Record of Spreading-Ridge and Flat-Slab Subduction Processes, Cenozoic Forearc Basins, Alaska.” Geosphere 11, no. 3 (2015) : 823-849.

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