Assessing controls on forearc basin subsidence

In collaboration with Dr. Stephan Graham


Low and high density turbidites, Great Valley Forearc, California

Forearc basins are important sediment archives for understanding continental dynamics because they preserve the tectonic, erosional and magmatic record of convergent margins. However, the tectonic forces that drive subsidence in forearc basins are poorly understood. This research seeks to determine the relative contribution of a variety of end-member subsidence mechanisms that act on forearc basins by using the California Great Valley forearc basin as the natural laboratory. Specifically, this study will (1) use subsurface stratal geometric relationships and spatio-temporal changes in basin fill thickness to reconstruct the basin geohistory and constrain the primary subsidence mechanisms acting on the Great Valley forearc, (2) quantify the 3D spatial patterns, timing and rates of subsidence in the basin, and (3) use these results to define a framework for interpreting subsidence trends in other ancient and modern forearc basins. The primary data utilized in this study are high-resolution 2D and 3D reflection seismic surveys and borehole datasets. The analysis and combination of these data will permit the first 3D subsidence reconstruction of the Great Valley forearc.



Wind River Range, Wyoming

Extracting t-T histories from highly variable zircon He datasets

In collaboration with Dr. William Guenthner, Dr. Andrew Laskowski, and Dr. Peter Reiners.

Recent advances in the understanding of He diffusivity in zircon provide new opportunities to extract thermal histories from regions with which experienced multiple and prolonged thermal events using the zircon He method. We are currently working on new thermochronologic constraints on the time-Temperature history of the northern Rocky Mountain region in Wyoming.

Check out our article in EPSL: Orme et al. 2016 

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Summary abstract from Orme (2017) depicting the timing and magnitude of forearc basin burial and exhumation


Exhumation of the Indus-Yarlung Suture Zone (IYSZ) Many of the rocks found along the IYSZ were deposited at or near sea level, but today sit at elevations greater than 5000 m. In addition, many of these rocks show evidence for deep burial prior to exhumation and uplift. I seek to resolve the time-temperature history of the IYSZ through the application of multiple low-temperature thermochronmeters, including Apatite and Zircon Helium dating. Check out my article in Geoscience Frontiers: Orme (2017). 


Xigaze forearc basin at 5400 m, southern Tibet




OLDER PROJECTS (Prior to 2016)

Xigaze Forearc Basin, southern Tibet The Xigaze forearc basin in southern Tibet, one of the largest and best-preserved forearc basins on Earth, records upper-plate processes active prior to and following the inter-continental collision between India and Asia. However, the understanding of the timing and mechanisms of forearc development and its evolution following collision is spatially and temporally limited. Fundamental questions remain concerning how the basin formed, its paleogeography prior to collision, its subsidence history and the thermal history of the basin following the initial and ongoing continent-continent collision. Answering these questions is important to reconstructing upper plate dynamics during active subduction of oceanic and continental lithosphere. This research addresses the Early Cretaceous to Pliocene history of the Xigaze forearc, using field mapping, sedimentology, sandstone modal petrography, geohistory analysis, U-Pb detrital zircon geochronology, and low-temperature thermochronology (apatite and zircon (U-Th)/He and fission track). This work is now published in Basin Research (Orme et al. 2015) and Journal of Sedimentary Research (Orme and Laskowski, 2016)

Apatite “Grunge” In collaboration with Kendra Murray and Dr. Peter Reiners

(U-Th)/He dates of apatite grains from some environments display significantly more dispersion than predicted by known sources such as varying grain size, radiation damage, or parent-nuclide zoning. In addition, many of these apatites show secondary external phases which contain significant amounts of U-Th relative to the apatite. Our research seeks to understand the potential impact of these U-Th-bearing phases on AHe dates. This work is now published in Chemical Geology (Link: Murray et al. 2014).

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Sweet “grunge” on the edge of an apatite crystal!