Bahia Grande is a large lagoon located within Laguna Atascosa National Wildlife Refuge in Cameron County, Texas. When the Brownsville Ship Channel was built along the southern end of the lagoon in 1936, Bahia Grande was cut off from the marine water of Laguna Madre. Since that time, Bahia Grande has been primarily dry with only ephemeral fresh water coming from heavy rainfall events, resulting in a severe decline in biological productivity. A restoration project led by the U.S. Fish and Wildlife Service has proposed to cut new channels between Bahia Grande and the Ship Channel to restore the connection with Laguna Madre. This is a large-scale project with major implications for the water quality, surrounding ecology, and associated biota in the region. Unfortunately, because very little is known about Bahia Grande prior to isolation, it is difficult to predict whether the results of the restoration will be comparable to the pre-Ship Channel environment. Paleoecological data provide the best opportunity to understand what Bahia Grande was like in the past. This study uses statistical analyses of the molluscan death assemblages from Bahia Grande to gain a better understanding of the environmental conditions in the lagoon before it was isolated. The first question addressed is how does Bahia Grande relate to other water bodies on the Texas coast? This may provide a modern analog to the past conditions in Bahia Grande. The second question inquires whether there are any local patterns or variations within Bahia Grande and several smaller surrounding lagoons. These results provide an important baseline for comparison with the restored lagoon. The results of this investigation show that, in a regional context, Bahia Grande was most similar to Alazan Bay and Baffin Bay, which are mostly enclosed shallow bays with high salinities due to the arid climate and limited freshwater inflow. Within Bahia Grande, there are several distinct molluscan assemblages. Salinity and water coverage are the most likely environmental factors responsible for the differences within Bahia Grande. Additionally, data from surrounding lagoons strongly indicate that some connections with Bahia Grande existed in the past.

Thanks to previous work conducted by Staff et al. (1986), Copano Bay on the Texas coast presents an exceptional research area for studying 1) the effect of living volatility on death assemblage diversity and composition and 2) the stability of death assemblage diversity. Staff et al. (1986) revisited one site in Copano Bay every six weeks for 18 months in 1981-1982. In order to test the variability of both the live and dead assemblages of Copano Bay, Texas, the transect originally established by Staff et al. (1981) in 1981-1983, was reestablished in 2004 and sampled every six weeks for a duration of one year. Taxonomic abundance, diversity, and composition of these assemblages were compared to each other and those of Staff et al. (1981) in order to understand how both the living and dead assemblages have changed in the intervening 22 years. Important findings include: 1. Death assemblage composition in Copano Bay changed over 22 years more than expected based on short-term variation; 2. The death assemblages in Copano Bay reflected changes in taxonomic composition of the corresponding living community; 3. The death assemblages of Copano Bay were found to predominantly reflect the local, rather than the entire regional, species pool; and 4. Variation in diversity occurred at both six-week and 22-year time scales, indicating that the death assemblages at the study site are variable. Understanding time averaging and its effects on death assemblages will not only aid in paleocommunity reconstruction, but also aid in the construction of modern ecologic baselines.

Thesis (Ph. D.)--University of Oregon, 2001. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 145-170). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph. D.)--Syracuse University, 2009. / "Publication number: AAT 3385841."

<p> Recent studies have used ecomorphological methods to look at morphological variation in artiodactyl postcranial elements as indicators of paleoenvironment conditions. From these studies, a continuum of variations in the lower limb bones of members of Bovidae and Cervidae in association with habitat conditions have been developed. The focus of this study is to look at variation in a single species, white-tailed deer (<i>Odocoileus virginianus</i>), that occupies a wide range of habitats and determine if regional adaptations exist in populations of different habitat conditions. </p><p> This studies uses linear measurements to assess size and shape variations in the metacarpal, metatarsal, astragalus, and calcaneus between white-tailed deer populations associated with open- and closed-habitat conditions thought-out the Holocene and in modern populations. The Holocene was subdividing into three time units (10,000-5,000, 5,000-3,000, and 3,000-1,000 yr BP) based on environmental shifts and availability of samples. Variations in size and shape were assessed for 1) in open- and closed-habitat conditions in both Holocene and modern deer overall, 2) in habitat conditions in open-classified Holocene deer through time, 3) in modern deer populations along a latitudinal transect,4) between Holocene and modern deer overall, and5) in Holocene and modern for open-classified and closed-classified deer. </p><p> Results indicated that size differences existed between open- and closed-classified deer in both Holocene and modern populations and that deer associated with open-habitat were larger. Shape differences between open- and closed-classified deer in the Holocene appear to be adapted to the environment, however, modern deer offered only limited insight and lacked consistence in variations. Results for variation thought time in Holocene deer indicated that size increased from Early to late Holocene in both the astragalus and calcaneus. Results for shape offered limited and mixed results. Results for variation in population along a latitudinal transect indicated that deer size increase from lower to higher latitudes. Results for shape differences between populations offered limited insight into variation. However, results for the calcaneal tuber functional region did indicated that deer become more open-adapted in relation to the southern population from lower to higher latitudes,. For the comparison of Holocene and modern deer size overall, only the astragalus indicated a clear variation between the two. The astragalus indicated that Holocene deer were larger than modern deer. Results for variation in shape between the two indicated little difference between the two except for the calcaneus, which indicated that modern deer were more open-adapted. Results for size differences in Holocene and modern for open-classified and closed-classified deer offered limited and mixed results. Results for shape differences were also limited; however, the calcaneus strongly indicated that modern closed-classified deer are more open-adapted than Holocene closed-classified deer.</p>

With a radiometric age of 396 ± 12 ma, the Rhynie Cherts, Grampian Region, Scotland, are the oldest unequivocal surface expression of an epithermal system in the world. Data is presented from 8 cored boreholes drilled within 100m of the Rhynie Cherts subcrop. The cherts are present in the upper part of the Lower Devonian basin infill which forms the Rhynie outlier. The basin is a half-graben structure, with a northeast/southwest trending western boundary, following the regional stress trend. In the area of the Rhynie Cherts, the western boundary is complicated by a series of cross faults. The eastern boundary is unconformable. The basin infill, in the area of Rhynie village, is a fining upwards sequence, produced locally from the newly formed Caledonide mountains. The basal Pre-Lava Sandstones Unit is an alluvial fan deposit. This is overlain by a series of basaltic andesite lavas with associated agglomerates and lapillistones. The Tuffaceous Sandstones Unit, containing both airfall and fluvially reworked tuffaceous material was deposited at the close of volcanic activity. The next unit in the series is the Shales with Thin Sandstones Unit, which contains the Rhynie and Windyfield Cherts. These two units of the post-lava sequence represent alluvial plain deposition, with evidence for sub-aerial exposure. The uppermost unit in the outlier is the Quarry Hill Sandstones unit, comprising fluvial channel sandstones. Hot spring activity occurred during the deposition of the Shales with Thin Sandstones Unit, resulting in the deposition of the Rhynie and Windyfield Cherts. A 35m cored borehole permits study of a vertical section through the chert bearing strata.

Results from the palaeoenvironmental investigations into the Holocene vegetation history of three sites in eastern lowland Scotland are presented. Two of the sites, Cruvie and Pitbladdo, are located in north Fife; the third site, Methvern is situated in south Perthshire. Cruvie is located in a kettle-hole and provides data extending from the Late-glacial to ea. 3900 BP. Pitbladdo is a former bog and cores from this site provide data on the period from ca. 8000 to 3900 BP. Methvern is a well-maintained raised bog and provides data that spans the entire Holocene. Relative, concentration and pollen preservation data are supplemented by loss-on-ignition, pH and magnetic susceptibility analyses. Microscopic charcoal data are also recorded. Radiocarbon dates allow comparisons to be made between similar events at different sites, resulting in a detailed picture of temporal and spatial patterns of palaeoecological change within a small geographical area. Attention is focused upon the identification of human impact on the environment during the early to mid Holocene. The influences of succession and climate change in determining patterns of vegetation change are also considered. The data obtained indicate that human activity may have had a limited impact on the environment in this area during the Mesolithic, but no unequivocal evidence is recorded. Anthropogenic impacts are more clearly identified during the Neolithic period and from the late Neolithic/early Bronze Age, human activity is considerable and includes pastoral and mixed farming. The value of tephra as a dating tool in this area of eastern Scotland is considered. The absence of tephra at the three sites investigated has led to the formulation of a hypothesis linking patterns of orographic rainfall and tephra deposition within Scotland. The study highlights the difficulties of determining the causal factors of vegetation change and the limitations of palaeoecological data in the identification of anthropogenic activity during the early Holocene. The recognition of climate signals is discussed and the routine counting of microscopic charcoal at all sites is proposed. It is suggested that further research is required to clarify the boundaries of tephra deposition in Britain. Finally the diverse patterns of change recorded within the study area emphasise the need for a network of closely spaced and well dated palaeoenvironmental sites covering the regions of Scotland, leading to the recognition of local patterns of environmental change.

<p> Investigation of decapod fossils from the Pawpaw Shale, Albian, Texas, has yielded 17 new species, and seven new genera. In total, 14 brachyuran; 3 astacidean; 4 anomuran; 8 axiidean; 5 palinuridean, and one stomatopod species were described and classified according to the latest classification scheme. Shale samples from a single locality in Fort Worth were analyzed for their grain size, mineral and trace element content. The Pawpaw Shale consists of sediments derived from the Llanos uplift to the southwest of Fort Worth, and represents a fining upward sequence deposited in a restricted lagoonal environment. The decapod fauna of the Pawpaw Shale is one of the richest decapod faunas of Albian age known to date, composed of a population of adult and juvenile crabs and lobsters. The peculiar small size of the individual lobsters of this fauna is attributed to their representing an early ontogenetic stage. No trace elements known to affect the biology an physiology of extant decapods could be found in the shale samples analyzed to indicate an environmental cause for the reduced size of the Pawpaw lobsters.</p>

No description available.

Organisms that grow by skeletal accretion contain a geochemical record of environmental conditions--they are, in effect, biological chart recorders. Thus, shell-bearing organisms are an important source of data on modern and ancient environments. Geochemical analysis of shell material sampled along an ontogenetic profile can provide time-series of the environmental variation experienced when the organism was growing. However, variations in growth rates and complete cessations of growth can bias biogeochemical archives. Thus, careful calibration of environmental conditions with shell growth is critical if reliable records are desired. Here, I present several studies designed to understand the relationship between bivalve shell growth and environmental variation. This is accomplished through careful calibration of temperature, geochemical variability, and growth increment variation (sclerochronology). I then apply the findings of these calibration studies to address paleobiological and paleoclimatic questions. I conducted a cross-calibration study relating annual temperature variation with stable oxygen isotope (δ¹⁸O) variation. I used daily increments to assign dates to each δ¹⁸O sample. I then compared the geochemically based temperature estimates with the actual temperatures from the same dates. Results indicate that combined geochemical and sclerochronological analyses can provide reliable estimates of environmental variation, as well as shed light on aspects of the clam's biology, such as the rate and timing of shell growth. The results of this study were then incorporated into a more generalized investigation of the relationship between annual temperature variation and growth rate. This study indicates that the resolution and fidelity of geochemically based environmental reconstructions depends strongly on growth rate and duration. Together, the results of these studies were applied to address paleobiological and paleoclimatic issues. First, I used sclerochronologically calibrated annual isotope profiles to detect time-averaging and spatial mixing. This study indicates that short duration time-averaging (<50 years), previously undetectable using traditional dating techniques, can be identified using oxygen isotope variation. Results also suggest that within-habitat spatial mixing can be detected. Results of the calibration studies were also applied to paleoclimate questions. Seasonality is an important aspect of paleoclimate reconstruction and is often inferred from annual oxygen isotopic variation in fossil shells. However, because many organisms do not grow throughout the year, their shells do not record the full range of seasonal temperatures. This limitation can be overcome by using stable oxygen isotope variation from two species, each of which continues to grow while the other has shut down. The method was demonstrated using two common venerid bivalves from the eastern Pacific. The reconstructed estimate of seasonality matches published sea-surface temperature data from the same site. I also used differences in δ¹⁸O values and daily increment numbers from modern and Pleistocene (last interglacial, ∼125,000 ybp) bivalves to estimate temperature change in the shallow marine environment off the coast of southern California. Data indicate that temperatures were∼3°C cooler than present, however, more data are needed to confirm these initial results.