Effect of Dam Emplacement and Water Level Changes on Sublacustrine Geomorphology and Recent Sedimentation in Jackson Lake, Grand Teton National Park (Wyoming, United States)

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 137Cs, 210Pb, and reservoir-corrected 14C 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

Newly recognized quaternary surface faulting and folding peripheral to the new madrid seismic zone, central united states, and implications for restraining bend models of intraplate seismic zones

A newly recognized thrust and nearby asymmetric anticline crop out 40 km north of Memphis, Tennessee, and they deform Eocene through Quaternary strata. These east–west-striking, south-verging structures are peripheral to the New Madrid seismic zone (NMSZ) of central North America, the source of M71 earthquakes in 1811–1812. The thrust dips ∼207 N and has 55 m of throw in Eocene strata. An angular intraformational unconformity indicates most deformation was Eocene. The anticline’s limbs dip 77 N and 227 S and fold Eocene and Pleistocene strata. Pleistocene sediments are dropped at least 4 m into a graben along the fold axis. Holocene sediment is ponded upstream from the fold axis, suggesting Holocene activity. Based on outcrops, well logs, and seismic reflection, we interpret the anticline as a fault-tip fold above a splay of the thrust fault. We interpret these thrusts in the context of a previously published sandbox model of a restraining bend uplift, which we apply here to the Reelfoot Rift fault complex. Using the eastern rift margin as the strike-slip fault of the sandbox model, the periphery of the model uplift has an east– west-striking, south-verging oblique-slip thrust where the actual thrust and anticline crop out. These results suggest that young thrust faults may be common along the periphery of the NMSZ and similar active intraplate restraining bends, that the eastern margin of the Reelfoot Rift may have been a principal strike-slip fault of the restraining bend, and that the seismic zone was active as early as Eocene

In utero administration of Ad5 and AAV pseudotypes to the fetal brain leads to efficient, widespread and long-term gene expression

The efficient delivery of genetic material to the developing fetal brain represents a powerful research tool and a means to supply therapy in a number of neonatal lethal neurological disorders. In this study, we have delivered vectors based upon adenovirus serotype 5 (Ad5) and adeno-associated virus (AAV) pseudotypes 2/5, 2/8 and 2/9 expressing green fluorescent protein to the E16 fetal mouse brain. One month post injection, widespread caudal to rostral transduction of neural cells was observed. In discrete areas of the brain these vectors produced differential transduction patterns. AAV2/8 and 2/9 produced the most extensive gene delivery and had similar transduction profiles. All AAV pseudotypes preferentially transduced neurons whereas Ad5 transduced both neurons and glial cells. None of the vectors elicited any significant microglia-mediated immune response when compared with control uninjected mice. Whole-body imaging and immunohistological evaluation of brains 9 months post injection revealed long-term expression using these non-integrating vectors. These data will be useful in targeting genetic material to discrete or widespread areas of the fetal brain with the purpose of devising therapies for early neonatal lethal neurodegenerative disease and for studying brain development