Physical Sciences and Mathematics Commons^™

Reinterpreting The Tectonic Model Of The Southern Part Of The Taconic Orogeny Through A Provenance Study Of Late Ordovician Sandstones, Juan Carlos Guerrero

LSU Master's Theses

A provenance study of quartz arenites that stratigraphically are closely associated with major Ordovician K-bentonites has been conducted in order to further our understanding of the tectonic setting of eastern Laurentia during the Late Ordovician. Using laser ablation ICP-MS, detrital zircons separated from Ordovician sandstone samples in the southeastern Appalachian Mountains (Virginia to Alabama) were dated using U-Pb geochronology. Analytical results show three dominate age ranges for the zircons from these sandstones: ~440-490 Ma, ~900-1300 Ma, and ~1300-1500 Ma. In addition, some zircon ages grouped into older ranges of ~1600-1800 Ma, ~1800-1900 Ma, and ~2600-2800 Ma. Zircon ages from ~900-2800 …

Sandy Dredge Pit Sedimentation – Characteristics And Processes In Caminada Borrow Area, Ship Shoal, Louisiana Shelf, Usa, Zehao Xue

LSU Master's Theses

Mississippi River Deltaic Plain’s barrier islands are undergoing rapid disintegration due to high rates of subsidence and a deficit in coastal sediment supply. To mitigate for barrier island land loss, Louisiana has implemented a restoration program that supplements coastal sediment deficits by introducing sand from outside of the active coastal system. Ship Shoal is an inner-shelf submarine shoal with large amounts of restoration quality sand that was dredged in 2013-2016 for the Caminada Headland Restoration Project in central Louisiana, USA.

Vibracore samples (1.5 - 3.5 m deep) collected in 2017 and 2018 in Caminada Borrow Area revealed new silts and …

Multicomponent Model Of Crustal Stress At Cajon Pass, Southern California With Implications For Stress Field Heterogeneity, Elliott Conley Helgans

LSU Master's Theses

Earthquake processes in plate boundary settings are chiefly controlled by the in situ crustal stress field. Knowledge of the relative importance of various active processes acting on a fault system is necessary to understand the mechanics of faulting. This is of extreme importance to the Cajon Pass region of southern California, which may function as an earthquake gate, imposing control on large multifault ruptures. We model the in situ stress field at seismogenic depth in Cajon Pass by balancing the orientation of the modern stress field inferred from earthquake focal mechanisms against the superposition of the far field tectonic driving …

Rare Earth Geochemistry Of Apatitic Fossils From The Middle-Upper Ordovician Southern Margin Of Laurentia, Rafael Adrian Villanueva

LSU Master's Theses

Widespread deposition of phosphate and a transition from tropical to cool water carbonates is seen throughout Middle-Upper Ordovician Nashville Dome area spanning the M4/M5 sequence boundary. Hypotheses explaining the onset of these lithologic changes have included the onset of glaciation, drawdown of CO₂ related to the Guttenburg Isotope Carbon Excursion (GICE), and siliciclastic weathering, yet none of these studies have provided definitive evidence that shows any of these are the sole factor driving paleoenvironmental changes across the M4/M5 boundary. In order to test whether rapid subsidence along the southeastern margin of Laurentia may have caused an influx of phosphate …

Spatiotemporal Variation Of Benthic Silica Fluxes In The Ngom Shelf, Byron Ebner

LSU Master's Theses

Dissolved silica (DSi), plays an important role in regulating primary productivity of silicifying organisms, such as diatoms which precipitate hard parts composed of biogenic silica (bSi) in coastal and shelf ecosystems fed by major rivers. In the Northern Gulf of Mexico (NGOM), loading of nitrogen and phosphorous have increased compared to a decline in DSi in the Mississippi River. Continued decreasing in DSi loading could lead to limited diatom growth and production or shifts in community composition, therefore, it is important understand the role of benthic fluxes in providing silica to the overlying water column as there are few regional …

Suspended Sediment Transport Revealed By Patterns In Turbidity And Electrical Conductivity Curves In Three Cave Systems In Missouri, Usa., Caroline M. Mierzejewski

LSU Master's Theses

In cave streams, the movement of sediment as suspended and bed loads are linked to the occurrence of precipitation events on the surface. During precipitation events, the discharge of the streams in the basin increases. As those surface streams flow into cave streams via sinkholes or fissures, the discharge in cave streams increase. In addition to changes in discharge, the response of the surface and cave streams to precipitation include changes in turbidity and electrical conductivity of the stream water.

Changes in turbidity (Tu), electrical conductivity (EC), and discharge (Q) of water in the cave stream can be used to …

Exploring Geochemical Proxies For Identifying Cryptic Sequence Boundaries In The Geologic Past Using Modern Bahamian Analogues, Evan B. Magette

LSU Master's Theses

Previous studies of carbonate diagenesis have suggested that bulk Sr concentrations and inorganic δ¹³C values may be a useful proxy for identifying cryptic sequence boundaries in meteorically altered limestones due to geochemical processes associated with carbonate mineral stabilization in cement precipitation in the meteoric diagenetic environment. However, it is possible that natural geochemical variation in sediments may produce geochemical shift which could be misinterpreted as a cryptic sequence boundary. To test this, the Two Pines roadcut containing a previously identified protosol on Eleuthera, Bahamas, which has been affected by vadose meteoric diagenesis was sampled for bulk geochemical analysis. …

Reflector Dip Trends In Seismic Sh-Wave Imaging Of A Modern Lower Mississippi River Point Bar, Adam Gostic

LSU Master's Theses

Various studies of ancient point bars have noted that a relationship can be observed between the dip angle and grain size of point bar lateral accretion deposits, with the most mud-rich deposits tending to exhibit the greatest dip. No analysis and only cursory explanations for this relationship have been provided. Additionally, buried mid-channel bars are absent from typical models of point bar architecture.

We successfully image the architecture of late-stage point bar deposits with a near surface 2D seismic SH-wave reflection survey and generate an SH-wave velocity model of the subsurface in the study area in order to interpret the …