The sedimentary characteristics of raised beach deposits are a potential archive of past wave climate as well as processes acting on beaches. In this study I examine changes in the grain-size, grain roundness, and spatial density of ice-rafted debris from two sets of raised beaches on opposite sides of the Antarctic Peninsula (AP): Joinville Island along the Eastern AP (EAP), and Livingston Island along the Western AP (WAP). All beaches were labeled starting at the closest proximity to the modern shoreline. Overall, the 9 beaches on Livingston Island are stratified with poorly sorted clasts compared to the better sorted 21 stratified lower beaches and 15 unstratified upper beaches on Joinville Island. The dissimilarity likely reflects the difference in foreshore gradient between the two islands. The Joinville profile is steeper, allowing waves to break on the coastline with high energy while the Livingston profile is shallower, enabling wave attenuation before reaching the shoreline. Grains on the raised beaches of Joinville Island show an overall increase in roundness through time while grain size shows low variability. However, the roundness trend is interrupted at beaches 5, 13-15.5, and 28. Beach 5 exhibits less and beach 28 exhibits more rounding than the general trend. Less rounding of sediments within beach 5 could be explained by short open water seasons with an increase in sea ice while the opposite could hold true for beach 28. The transition between beaches 13 and 15.5 indicates a decrease in roundness over time, opposite the overall roundness trend. The ages of beaches 15.5-13 (~2.8-2.3 cal. kyr BP) coincides with the onset of the Neoglacial time period ~3 cal. kyr BP. The presence of sea-ice or increased glacial activity could hinder clast rounding or introduce less rounded materials during cooler periods associated with this Neoglacial time period. Grains within Livingston Island beach ridges also show an overall increase in roundness through time but no coherent trends in grain size. However, Livingston Island contains two types of beach deposits: strand plains and beach ridges, the latter of which are interpreted as storm ridges. Strand plains were deposited by normal swash processes and exhibit sub-angular to sub-rounded sediments. Typically, storm ridge sediments would be less rounded, characteristic of high energy storm deposits, than the strand plain deposits, roundness and grain size are uncorrelated. However, the beach ridges contain sub-rounded to rounded deposits while the strand-plain deposits are sub-angular to sub-rounded. Ground penetrated radar profiles through the beach ridge crests suggest they bury older strand-plain deposits. Therefore, I suggest the more rounded nature of the beach ridge deposits on Livingston Island is due to the recycling of older strand-plain deposits by storms.

The Permian redbeds of the Midcontinent U.S.A. are thought to contain important clues to the climate history of western Pangaea. However, before these units can be used as paleoclimatic archives, better constraints are needed on their age, depositional environment, and provenance. In this study, 43 stratigraphic sections were measured within the Lopingian Cloud Chief Formation of western Oklahoma. The sections were complemented by strontium isotope analysis and detrital zircon geochronology. Nine facies were recognized within the measured sections. These facies include massive gypsum, gypsiferous sandstones, channelized very fine sandstones, thickly-bedded sandstones, siltstones, variegated mudstones, ripple cross-laminated very fine sandstones, interbedded sandstones and mudstones, and silty claystones. These facies are interpreted to represent subenvironments of widespread arid-land fluvial systems flowing into a sabkha. These interpretations fit well with other recent work calling for arid conditions within the midcontinent during the middle Permian. Detrital zircon geochronology points to a dominant sediment source to the east (Ouachita Mountains) with a subordinate source to the west (Ancestral Rocky Mountains in Colorado and New Mexico). Strontium isotope values of the massive gypsum facies provide evidence for marine encroachment during periods of high relative sea level. These isotope values point to an age for the Cloud Chief of 262 ± 3 Ma to 255 ± 3 Ma, providing some of the first numerical ages from the redbeds of western Oklahoma.

Recent studies along the northwestern Gulf of Mexico document rapid back-stepping of estuarine environments of up to 20 km and 150 m/yr at ca. 8.2 thousand years ago (ka), 4.8, ka, and 2.6 ka. If such rapid changes in coastal environments occurred today along the urbanized coast of the Gulf of Mexico major economical and ecological loss would occur. Of these three backstepping events, only one can be tied to a known cause – the 8.2 ka event related to a rapid increase in the rate of relative sea-level rise. However, the cause of the latter two, the 4.8 and 2.6 ka events are largely unknown. To determine the relative roles of changes in sea level and climate in these two events, paleo sea-level (Chapter 2), climate (Chapter 3), and stratigraphic records (Chapter 4) are presented from upper Baffin Bay, Texas and neighboring playa Laguna Salada.

As commonly used high-resolution sea-level indicators are absent from the southern Texas Coast, a new sea-level indicator is needed. I test the use of intertidal microbial mats in reconstructing Holocene sea levels from Baffin, Bay Texas (Chapter 2). The indicative range of microbial mats is ±0.29 m, much less than the ±2 m indicative range of typical sea-level indicators currently used along the semiarid Texas coast. The elevations of 22 buried radiocarbon-dated microbial mats plot within error of relative sea-level data derived from the central Texas coast for the past 5.0 ky indicating that microbial mats provide a robust proxy for paleo–sea levels along semiarid and arid coastlines. The high-resolution microbial mat relative sea-level record derived from the tectonically stable central Texas coast also provides a test of recently proposed Holocene Highstands based on emergent coastal deposits in Texas and Alabama. The microbial mat relative sea-level data, similar to relative sea-level data derived from Mississippi Delta basal peats and lower-resolution Texas estuarine bivalves, indicates an ever-decreasing rate of relative sea-level rise since ca. 5.0 ka and precludes the possibility of Holocene Highstands in the northern Gulf of Mexico.

Paleoclimate records are also sparse along the southern Texas coast. A new quantitative drought proxy is derived from a transfer function between X-Ray Fluorescence (XRF) elemental data from a Texas playa and a tree-ring drought record (Chapter 3). Using this transfer function, a 954-year tree-ring drought record was extended to ca. 3,000 ka. Ba, Br, and Pb were utilized as predictor variables. Machine learning algorithms, utilized to derive the transfer function, had maximum validation accuracies of 94%. Changes in the extended drought record correspond with the timing of the Roman Climate Optimum, Medieval Warm Period, Little Ice Age, and changes in North Atlantic sea surface temperatures (SST). Increased drought frequency is coeval with nearby dune migration ca. 0.2 ka, 1.9 ka, and 2.6 ka. The highest drought frequency in the record occurs during the Medieval Warm Period ca. 1.0 ka followed by a decrease in drought frequency during the Little Ice Age ca. 0.4 ka. Increased drought frequency accompanies increased North Atlantic SST since 3 ka. This trend of warm North Atlantic SST and dry conditions over the study area follows secular meteorological observations and tree-ring records. These results indicate that lacustrine derived XRF element data can be used as a quantitative tool to reconstruct past drought records, and that North Atlantic SST modulated drought in southern Texas for the last 3,000 years.

Within Baffin Bay, five flooding surfaces making periods of abrupt environmental change, between 1.1 - 1.0 ka, 2.7 - 2.1 ka, 3.8 - 3.0 ka, 5.2 – 4.9 ka, and 6.5 – 5.7 ka occur through a time-period of ever decreasing rates of relative sea-level rise and within error of periods of drying in southern Texas at ca. 1.0 ka, 2.6 ka, 3.4 ka, 4.8 ka, and 5.5 ka (Chapter 4). I hypothesize that these flooding surfaces, occurring when sea level in the Gulf of Mexico was rising < 2 mm/yr, and during independently documented drying events, were primarily driven by changes in climate through declines in fluvial sediment supply to the coast.

Beach ridges and other prograding beach deposits are important sedimentary archives of past floods, storms, and relative sea-level changes. Accurate interpretations of beach ridges requires an understanding of their formation and preservation through time. In the following studies, I use ground-penetrating radar to observe the stratigraphy of beach ridges and prograded beach deposits. Additionally, I employ the use of elevation surveys, aerial photographs, radiocarbon dating, and optically stimulated luminescence dating to understand the timing of events preserved in the sedimentary record.

In Chapter 2, I explore the formation of swash bars on the Elwha River delta after the removal of two dams on the fluvial system simulated a large sediment pulse to the system, similar to a flood or landslide. I find that mouth bars form most often after higher than average discharge events in the fluvial system, and swash bars form soon after due to wave reworking of the mouth-bar sediments. However, only 10 of 37 swash bars that formed were preserved at the time of my GPR survey, five years after dam removal. Additionally, the swash bars that did survive amalgamated with one another, forming a large barrier at the delta front, indicating that in small mountainous river settings, beach ridges may be more indicative a large sediment pulse to the system, rather than a single flood.

In Chapter 3, I examine the ~600-year sedimentary record of the coastal Oxnard Plain. Progradation on the Oxnard Plain has been relatively constant on centennial (150- to 200-year) timescales, prograding at rates of 0.3 to 1.4 m a-1. However, on shorter timescales, progradation is episodic, with greater progradation occurring after high discharge events along the Santa Clara River. Extended droughts remove up to 90 m of the beach, equivalent to ~5 to ~120 years of the sedimentary record. Additionally, I image beach cusps in shore parallel GPR profiles, which previously had not been recognized in GPR profiles.

Lastly, in Chapter 4 I use gravel beach ridges to reconstruct the relative sea-level (RSL) record on Joinville Island, Antarctica. I find that RSL has fallen ~5 m over the last ~3000 years, at variable rates throughout the late Holocene. I interpret that ice mass loss, similar to the scale of ice mass loss after the 2002 Larsen B Ice shelf collapse, and ice mass growth caused by glacial advance, both occurred in the Late Holocene and were recorded in my RSL reconstruction. Therefore, global- and continental-scale global isostatic adjustment models, which currently only account for ice changes on thousand-year timescales, are missing crucial centennial-timescales ice mass changes.

The economic importance of coastlines highlights the need to understand how coasts evolve in response to changing climate. Prior work suggests that many of the estuaries in the northwestern Gulf of Mexico underwent large changes at 2.6, 4.8, and 8.2 ka. Twenty-eight vibracores, eight Geoprobe cores, twenty-eight radiocarbon ages, and twenty-five kilometers of seismic profiles were used to determine the response of the Nueces Bay-head Delta to the 2.6 ka and 4.8 ka events. Within the cores we identified nine sedimentary facies representing five distinct deltaic environments. Within the 25 kilometers of seismic data, we identified five seismic facies that correspond to the deltaic environments identified within the sediment cores.

Fifteen sand lobes interpreted to be buried mouth-bar deposits identified in the seismic profiles and cores were used to track changes in the location of the seaward edge of the delta through the middle to late Holocene. Following progradation of the delta at 7.5 ka, the delta underwent two backstepping events in which the delta front transgressed up to 20 km at 4.8 ka and 2.6 ka. Following these two backstepping events the delta prograded up to 20 km seaward of the deltas maximum landward location. During delta progradation from 4.8-3.2 ka delivering 8.3x103 m3/yr of sand was delivered to the delta. During delta backstepping from 3.2-2.6 ka 6.5x103 m3/yr of sand was delivered to the delta. During the last phase of delta progradation from 2.6 ka-present delivering 6.6x103 m3/yr of sand was delivered to the delta. The decrease in the volume of sand delivered to the delta during the backstepping event at a time when the rate of sea-level rise as sea-level rise was decreasing and regional records of climate show drying suggests that the backstepping events were likely driven by climate changes.

The highly developed and populated coast of southern California is at risk for inundation due to storms or tsunamis; coastal erosion; wildfires; earthquake-driven shaking, liquefaction, and subsidence; sea-level rise; and other hazards. Estuaries formed during periods of sea-level transgressions often record environmental changes that have affected the region over time. These records of past climate, sea level, inundation events, and other changes can provide a baseline with which to compare current changes. Past recurrence intervals of hazard events also provide an estimate for how often and at what magnitude we can expect events to recur in the future. Here we compile relative sea-level indicators from other studies on southern California estuaries to show that relative sea level in southern California has risen 0.8 ± 0.3 mm/yr over the last 4000 years, less than modern rates and predicted future rates of sea-level rise. Predicted acceleration of sea-level rise could exacerbate the effects of storm and tsunami inundation along the coast.

We use a variety of biological, sedimentological, and geochemical measurements on sediment cores from Carpinteria Marsh, Carpinteria, California, to document environmental changes that have occurred along the Santa Barbara Channel over the last 10,000 years. We show evidence for at least 37 episodes of alluvial fan progradation due to large floods over the past 7 ka, clusters of which correspond to regional records of wet climate conditions. We also show evidence for one coseismic subsidence event at 1.0 ± 0.1 ka, which may correlate with records of other earthquakes in the region. Finally, the topmost sediments within the marsh record environmental changes within the historical period. Within these sediments, we use a multi-proxy approach to document the history of the marsh over the last 200 years including the appearance of European pollen species, makers of industrialization, and an overwash deposit related to the 1861-2 winter storm season in California.

Beaches are preserved above sea level along ice-free portions of the Antarctic coastline due to post-glacial rebound associated with glacial isostatic adjustment since the Last Glacial Maximum. The ages and elevations of these beaches provide relative sea-level constraints for glacial isostatic adjustment models and ice-sheet histories. Due to harsh field conditions and difficulty dating Antarctic materials, a lack of geochronological constraints on raised beaches limits our understanding of relative sea level around Antarctica. The focus of the studies discussed here is on Antarctic raised beaches with goals to improve the methods of dating cobble surfaces from raised beaches using optically stimulated luminescence and use the dated beaches to reconstruct relative sea level and better understand Antarctic coastal processes throughout the Holocene. Through a series of cleaning methods applied to sample carriers used for optically stimulated luminescence measurements of sediment, the contamination of dose-dependent, variable signals from sample carriers previously assumed to have neutral signals is eliminated through a series of cleaning methods (Chapter 2). An analysis of optically stimulated luminescence characteristics of quartz from cobble surfaces with sample petrology and cathodoluminescence provides insight on the suitability of Antarctic materials for optically stimulated luminescence dating (Chapter 3). The limited amount of quartz (<10%) found in the majority of the samples often occurs as intergrowths in feldspars characterized by irregular, anhedral crystal form. A lack of discernible relationship between optically stimulated luminescence and cathodoluminescence properties and petrology suggest that cathodoluminescence behavior and petrology are not responsible for the poor luminescence characteristics observed from quartz extracted from cobble surfaces. A relative sea-level history of Marguerite Bay, Antarctic Peninsula derived from optically stimulated luminescence-dated beach cobble surfaces further constrains post-glacial rebound since the Last Glacial Maximum (Chapter 4). New ages suggest the Holocene marine limit for Marguerite Bay is 21.7 masl with an age of ~ 5.5-7.3 ka. Our favored hypothesis for the ages of the beaches from 21.7-40.8 masl at Calmette Bay is that the beaches formed prior to the Last Glacial Maximum. The temporal distribution of circum-Antarctic raised beaches throughout the Holocene is utilized to determine the relationship between wave-energy, sea ice, and coastal evolution (Chapter 5). The distribution of raised beaches throughout the Holocene around Antarctica show synchronous periods of beach formation in the Antarctic Peninsula and the Ross Sea centered at 2.0, 3.5, and 5.3 ky BP while East Antarctic (outside of the Ross Sea) beach formation is out-of-phase with the rest of the Antarctica at 3.2, 4.2, 5.8, and 6.5 ky BP. The distribution of beaches in the South Shetland Islands is dominated by enhanced beach formation between 0.2 and 0.7 ky BP most likely due to rapid post-glacial rebound associated with the Little Ice Age with minor peaks in beach formation from 1.3-2.2, 5.1-5.6, and 6.0-6.5 ky BP. Beach formation results from higher wave exposure during periods of reduced sea ice observed from comparison with Holocene sea-ice proxies. The anti-phasing of beach formation in the Antarctic Peninsula and Ross Sea compared to East Antarctica is markedly similar to the phasing of modern and Holocene climate forcing around Antarctica. The findings of these studies focused on Antarctic raised beaches have implications for understanding sea-level, glacial isostatic adjustment, ice-sheet histories, and coastal processes since the Last Glacial Maximum.  

Raised beach ridges in polar environments are recorders of relative sea-level (RSL) change. The South Shetland Islands (SSI) contain large areas of ice-free raised beaches used to resolve paleo-sea-level change. The largest of these ice-free areas is Byers Peninsula (60 km2) on Livingston Island, SSI. This peninsula and other ice-free coasts within the SSI contain series of raised beach ridges correlated by age and elevation. The internal architecture of these beach ridges is critical to understanding paleo-RSL. The non-destructive method of ground penetrating radar (GPR) was used to investigate the internal architecture of the South Beaches of Livingston Island where a flight of nine beach ridges (five of which were the focus of in this study) have been glacio-isostatically raised since the last glacial maximum (LGM). Recalibrated radiocarbon ages collected from these and other beach ridges in previous studies are used to relate beach morphology and stratigraphy to the glacial history of the region. Over 10 km of 200 MHz GPR transects and synchronous GPS were collected over a two-week period in the spring of 2019. Sediment pits <1 m in depth were dug to search for dateable material and described for ground truthing of GPR reflections. Six key radar facies and three radar surfaces were identified: a seaward dipping progradational facies, a landward dipping overwash facies, a flat and concave down aggradational facies, a discontinuous hyperbola rich cobble facies, a flat lying lagoon facies, and a channelized fluvial facies. Erosional and toplapping surfaces were identified in addition to the top of the bedrock. Within this flight of raised beach ridges evidence was found of transgressive depositional patterns marked by progradational seaward dipping facies deposited during periods of RSL fall followed by erosion and overlying deposition of landward dipping overwash and aggrading beds. This succession is routinely located over a notch in the bedrock interpreted to represent a wave-cut feature. An apparent correlation between the ages of beach ridges and wave-cut notches with known neoglacial advances at ~5.5 ka, ~3-1 ka, and ~0.4 ka suggests that the influence of glacial-isostatic adjustment (GIA) on RSL is responsible for the origin of the beach ridges and the underlying wave-cut scarps. This GIA hypothesis further supports recent assertions of a much more dynamic RSL history for Antarctic coastlines, which may “contaminate” the LGM RSL signal across Antarctica.