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No description available.

No description available.

This study documents the vertical and lateral distribution of organic-walled phytoplankton cyst assemblages from samples taken from the Demopolis-Ripley transition interval, a pelagic carbonate to marine clastic facies transition in the Upper Cretaceous Selma Group of Mississippi and Alabama. The study samples have yielded abundant and diverse assemblages of dinoflagellate, chlorophyte, and acritarch cysts. In all, 70 species of organic-walled phytoplankton cysts are treated. On the basis of the ranges of the dinoflagellate cyst species recovered from the present study samples, the Demopolis-Ripley transition interval in the study sections is correlated with the lower Maastrichtian of western Europe. Also, on the basis of the data from the present study and other unpublished dinoflagellate cyst data, the Campanian-Maastrichtian boundary in the Selma Group is shown to lie at some point within the middle one-half of the Demopolis Chalk. The application of computer-based gradient analysis programs to a Recent dinoflagellate cyst dataset from the continental shelf of South Africa has shown that gradient analysis of organic-walled phytoplankton cyst assemblages can be useful in the recognition of patterns of marine watermass distribution. Finally, the application of gradient analysis techniques, including cluster analysis, polar ordination, mean rank abundance (MBA) analysis, and average member similarity (AMS) analysis, to the Demopolis-Ripley organic-walled phytoplankton cyst assemblages has allowed the recognition of four paleoecological significant phytoplankton cyst associations. The stratigraphic distributions of these associations correspond well to the changing distributions of watermass characteristics which are likely to have accompanied the Denopolis-Ripley facies transition. / Master of Science

The modern Maya lowlands are covered by a variety of vegetation types, ranging from freshwater swamps, through high "quasi rainforest," to open grasslands, each with its own exploitable potential and effect upon subsistence. Limiting factors such as pests, leaching, and competition would have decreased the potential harvests of prehistoric Mayan agriculture. Several ecologically sound methods, including increased crop diversity, mulching, and quarantine measures, reduce the impact of these limiting factors. Modern Maya agriculture is practiced at such low levels that it evades some limits to its potential productivity. Hypothesized prehistoric systems, such as intensive milpa, ramon cultivation, raised fields, and artificial rain forest, must have reached equilibrium with their biotic, climatic and edaphic environments. Using ethnographic and crop productivity data, with certain assumptions, quantified systems models of prehistoric agriculture have been derived. An ecologically compatible combination of intensive milpa, artificial rain forest, ridged fields, and marsh cultivation theoretically will support over 400 people per square kilometer of upland in the Peten. These data are within the limits of archaeological demographic estimates ranging from 40 to 900 people/km². Principal components analyses of pollen from edaphic and successional gradients serve as modern analogs for statistical comparison with two cores taken in the lake district of central Peten, Guatemala. Results indicate that agricultural activity, not climatic change, caused changes in the prehistoric vegetation. The Maya Classic landscape was an agriculture-dominated regime, with little untouched natural vegetation. Orchards, artificial rain forest and woodlots, although not supported by pollen evidence, may have covered much of the lowlands. The Maya collapse was followed by a general depopulation of the Peten. The Peten-Itza recolonization of the lake district, and the modern population influx appear as two minor agricultural episodes in a largely arboreal Postclassic landscape.

Twenty-eight samples were collected from the stratigraphic section exposed one kilometer east of Buff Bay, Jamaica. This exposure includes the upper part of the Montpelier Formation and the type locality of the Buff Bay Formation. Planktic foraminifers were identified in each sample and age determinations made. The age of the section studied is interpreted as ranging from upper N 13 (Globorotalia mayeri Zone) to N 16 (Globorotalia acostaensis Zone). The uppermost portion of the Buff Bay Formation, exposed in 'Dead Goat Gully,' is reported by other authors to contain N 17 fauna, but was not collected in this study Three-hundred specimens of benthic foraminifers were picked from each sample. From this population sampling, 431 species and subspecies were identified, described and photographed. The percentage of the total benthic fauna of each taxon was calculated for each sample A comprehensive paleobathymetric analysis was made of the Buff Bay Formation, using planktic/benthic ratios, generic dominance, faunal diversity, and comparative modern species distributions The depositional environment of the upper Montpelier Formation and the Buff Bay Formation is interpreted as middle to lower bathyal water depths / acase@tulane.edu

The systematics of two hundred and eighty-nine prosobranch gastropods from the early to middle Pleistocene Moin Formation of Costa Rica are treated. The paleoecology of most extant and some extinct species of these mollsucs is discussed, and a paleoecological reconstruction of the Punta Limon peninsula is made. The presence of recognizable communities on differing substrates within the ecological zonation of a fringing reef is shown, from the intertidal zone down to the inner shelf at the base of the reef system itself, where ultimate deposition of the Moin Formation occurred. The faunal composition of the Moin indicates the occurrence of species-rich faunas evolving during the Pleistocene interglacial times, each involving speciation events following the extinction events of intervening glacial pulses. Evidence is given for the presence of a western Caribbean subprovincial unit during the Pleistocene, which continues on to the present day / acase@tulane.edu

Conserving biodiversity in the current global ecological crisis requires a robust understanding of a multitude of abiotic and biotic processes operating at spatial and temporal scales that are nearly impossible to study on a human timescale and are therefore poorly understood. However, fossil data preserve a vast archive of information on past ecosystems and how they have changed through time. My PhD research is composed of three studies that look at biogeogaphic distribution, ecosystem structure, and trends in richness and diversity. Identifying organisms to the species level is a common practice in ecology when conducting community analyses. However, when species-level identification is not feasible, higher level taxonomic identifications are used as surrogates. This study tests the validity of supraspecific identifications for vertebrates in regional biogeography studies, using the recorded occurrences of terrestrial and aquatic taxa from 16 national parks on the Colorado Plateau and culling the data set based on a series of taphonomic processes to generated fossil assemblages. Changes in community structure as a result of increased magnitude and/or frequency of perturbations have been well documented in terrestrial and marine ecosystems. Unfortunately, the long-term effects of sea-level rise on vertebrate communities in coastal habitats are poorly understood and difficult to study on a human time scale. This study examines the long term effects of relative sea-level change on coastal plain ecosystems of the Belly River Group (Campanian) in southern Alberta using microvertebrate fossils. Most Cretaceous freshwater deposits in North America produce only a couple of articulated fish skeletons. Because of this preservational bias many workers suggested that freshwater teleosts were largely absent from North America until the Eocene or later. Late Cretaceous fish assemblages are of particular interest, because these assemblages undergo a major compositional change. Pre-Cretaceous fish assemblages are dominated by non-teleosts, while Paleogene assemblages are dominated by teleosts that are members of extant families. This study provides a first approach in characterizing long-term trends in richness and the distribution of Late Cretaceous, nonmarine actinopterygians of the Western Interior of North America.

Cupriferous swamps are characterized by high concentrations of copper in the soil and water. The Aboushagan swamp, situated 8km northwest of Sackville, New Brunswick is a unique metalliferous wetland where copper is naturally sequestered in the peat without having a significant negative effect on the vegetation. This paleoecological history of this region is not well known and few studies have attempted to characterize the local vegetation trends. This study investigates the post-glacial vegetation history of the swamp as well as any relationship it may have with the copper present in the peat. Surface peats (dry weight) have previously been found to contain up to 10% copper. This study found Cu content in two peat cores ranged from trace values to a high of 4800 µg/g and 25 000 µg/g (0.48 and 2.5 % dry weight copper). Despite the increased values, there was no detectable change in pollen due to copper concentration and any increase of copper in the peat material is likely a result of post depositional hydrological processes transporting copper into the layers of peat where it is being sequestered in the organic material and never becoming bioavailable to the surface vegetation. Pollen revealed that following deglaciation, the Aboushagan swamp began to develop as a rich fen around 10.7 ka BP that transitioned into a poor fen with Sphagnum around 9.9 ka BP as the wetland basin filled in. Around 8290 ka BP, temperatures warmed and the soil dried up leading to more canopy cover and fern abundance which yielded a mixed coniferous-deciduous swamp with Sphagnum in the understory that persisted until approximately 1.4 ka BP. Maritime vegetation trends in other studies describe a pine maxima (7.5 ka BP) and hemlock maxima (6.5-4.5 ka BP), neither of which were not found in the pollen record here due to a lack of peat accumulation between 8290 and 4350 ka BP. This is likely due to a regional climatic change that increased temperatures and decreased summer precipitation between 8 and 4 ka BP. In the last 1.5ka BP, the swamp has been dominated by spruce but other trees such as pine, fir, and birch have grown in abundance in the last few hundred years. A decrease in overall pollen abundance and concentration near the top of the core may be evidence for the little ice age event (1450 cal years BP). Today the swamp is a typical mixed coniferous-deciduous swamp with Picea mariana, Larix laricina, Acer rubrum, and Abies balsamea. An understanding of the swamp’s ability to sequester copper from becoming bioavailable has implications for the rehabilitation of contaminated industrial landscapes with wetland technologies. This study also highlights the high sensitivity with which wetlands can be used to detect and differentiate between autogenic (local) and allogenic (regional) climatic and vegetation changes while describing the vegetation community succession in the Aboushagan basin since the last deglaciation.

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