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The southern Appalachian Inner Piedmont (IP) has been interpreted to represent a relict crustal escape flow system that was active during the Neoacadian (370-340 Ma) orogeny. Critical to the support of this hypothesis is the identification of both the high-temperature, rheologically weak “channel,” with crustal flow driven by relatively low differential stress, and the rheologically strong “buttress,” where deformation was driven by relatively high differential stress. Paleopiezometric analyses from southern Appalachian quartz mylonites, quartzites, and quartz-bearing pelitic rocks of the eastern Blue Ridge (EBR; buttress) and IP (channel) allow gradients of differential stress driving flow to be examined. Samples located along a transect in the EBR northwest of the Brevard fault zone (BFZ) are used to define gradients in differential stress and deformation temperatures in the proposed buttress. Preliminary results for these samples suggest that deformation temperature increased, and differential stress decreased during deformation approaching the BFZ from the northwest. Mechanisms of quartz recrystallization shift from minor grain boundary bulging and dominant subgrain rotation (SGR) in samples located away from the BFZ to dominant SGR and minor grain boundary migration (GBM) in samples in the immediate BFZ footwall. Recrystallized grain sizes in the EBR are, in almost all cases, less than 150 microns on the major axis of ellipses used to approximate grain size. In the proposed crustal channel, quartz-rich samples collected along a transect south of Rosman, NC in the Brevard and Brindle Creek thrust sheets of the IP show GBM and SGR as the dominant mechanisms of deformation, as well as a general increase in grain size into the “core” of the proposed crustal channel. Recrystallized grain sizes in the Piedmont away from the BFZ commonly exceed 500 microns. These preliminary results suggest increasing deformation temperatures and decreasing differential stresses from close to the BFZ into the Piedmont, which is consistent with increased cooling of the proposed channel proximal to the colder, stronger Blue Ridge. Ongoing piezometric analyses, combined with quartz c-axis thermometry and thermochronology, may provide additional evidence to better refine the hypothesized buttress-channel relationship. 

Dam installation on a deep hydrologically open lake provides the experimental framework necessary to study the influence of outlet engineering and changing base levels on limnogeological processes. Here, high-resolution seismic reflection profiles, sediment cores, and historical water level elevation datasets were employed to assess the recent depositional history of Jackson Lake, a dammed glacial lake located adjacent to the Teton fault in western Wyoming (USA). Prograding clinoforms imaged in the shallow stratigraphy indicate a recent lake-wide episode of delta abandonment. Submerged ∼11–12 m below the lake surface, these Gilbert-type paleo-deltas represent extensive submerged coarse-grained deposits along the axial and lateral margins of Jackson Lake that resulted from shoreline transgression following dam construction in the early 20th century. Other paleo-lake margin environments, including delta plain, shoreline, and glacial (drumlins, moraines) landforms were likewise inundated following dam installation, and now form prominent features on the lake floor. In deepwater, a detailed chronology was established using 137 Cs, 210 Pb, and reservoir-corrected 14 C for a sediment core that spans ∼1654–2019 Common Era (CE). Dam emplacement (1908–1916 CE) correlates with a nearly five-fold acceleration in accumulation rates and a depositional shift towards carbonaceous sediments. Interbedded organic-rich black diatomaceous oozes and tan silts track changes in reservoir water level elevation, which oscillated in response to regional climate and downstream water needs between 1908 and 2019 CE. Chemostratigraphic patterns of carbon, phosphorus, and sulfur are consistent with a change in nutrient status and productivity, controlled initially by transgression-driven flooding of supralittoral soils and vegetation, and subsequently with water level changes. A thin gravity flow deposit punctuates the deepwater strata and provides a benchmark for turbidite characterization driven by hydroclimate change. Because the Teton fault is a major seismic hazard, end-member characterization of turbidites is a critical first step for accurate discrimination of mass transport deposits controlled by earthquakes in more ancient Jackson Lake strata. Results from this study illustrate the influence of dam installation on sublacustrine geomorphology and sedimentation, which has implications for lake management and ecosystem services. Further, this study demonstrates that Jackson Lake contains an expanded, untapped sedimentary archive recording environmental changes in the American West.