This study analyzes the pollen, spores, and algae in the upper 90 m section of a mostly continuous, well dated, 323 m core (OL-92) from Owens Lake, southeastern California. The entire core has produced a paleoclimatic record for the past ∼800 ka. The 90 m interval dates from ∼9 ka to ∼151 ka beginning with the penultimate glaciation and ending during the termination of the last glaciation. The record shows high amplitude fluctuations in the abundances of pine, juniper, saltbush, sagebrush, chenopods/amaranths, and Ambrosia-type pollen. High percentages of juniper pollen with low percentages of desertscrub pollen during the intervals ∼150 ka to ∼120 ka and 73 ka to ∼20 ka alternate with low juniper pollen and relatively high percentages of desertscrub and oak pollen during the intervals ∼118 ka to ∼103 ka and ∼18 ka ∼10 ka and into the Holocene. Sagebrush pollen varies with juniper pollen but has a tendency to lead it in time. Pine and fir pollen tends to vary inversely with juniper over the long term. These trends are interpreted as vegetation change in response to glacial-interglacial cycles: During cold-wet glacial climates there was a downslope expansion of juniper woodland and sagebrush scrub, contraction of Sierra Nevada mixed conifer forest, and displacement of warm desertscrub, suggesting average temperature and precipitation departures from modern values ranging from -2°C to -6°C and from +100 mm to +350 mm. Conversely under warmer and drier interglacials warm desert shrubs expanded their range in the lowlands, juniper and sagebrush retreated upslope, and the Sierran forests expanded. Estimated average temperature and precipitation departures from modern values ranged from -0.5°C to +3.7°C and +13 to -26 mm. Comparison of the pollen spectra spanning the penultimate and ultimate glacial maxima shows the former to have been longer and more intense, in accord with the Sierra Nevada glacial record. Similarly, the higher abundances of Ambrosia pollen during the last interglaciation, compared to the Holocene, indicate warmer temperatures in the former. The presence of high oak percentages also during the last interglaciation suggest an expansion of the summer monsoon. Finally, the match of the juniper curve with the marine oxygen isotope chronostratigraphy suggests a link between vegetation change in the southern Owens Valley and global climate.

The late Quaternary stratigraphy of three Paleoindian archaeological sites, located on the edge of Shaw Creek Flats in the middle Tanana Valley, Alaska, consist of up to 2 meters of calcareous eolian sand, loess, and buried paleosols. Two Paleoindian occupations at the Broken Mammoth, Swan Point, and Mead sites date from 11,800 to 11,000 yr B.P. and from 10,800 to 9500 yr B.P. Well-preserved faunal remains, worked mammoth ivory, stone and organic tools, and at Swan Point, the early occurrence of microblades dating to 11,700 yr B.P., are associated with buried paleosols at the base of the loess. Stratigraphic and radiocarbon-chronological correlations between the sites, and at similar geological sections, suggest the presence of a regionally-correlative, eolian stratigraphy consisting of three main units: (1) a basal gray eolian sand, overlying a deflated, ventifacted, bedrock surface, was deposited as bluff-top sand sheets probably during the Birch Period transition from periglacial steppe-tundra environments to shrub tundra about 12,000 to 14,000 yr B.P. (2) An overlying lower loess unit contains three paleosol complexes, classified as Typic Cryorthents, which consist of a series of cumulative Abk horizons overlying Ck loess parent material. The lower paleosol complex dates to 11,800 to 11,000 yr B.P. as is associated with the initial occupation of the sites. The middle paleosol complex dates from 10,800 to about 9500 yr B.P. and is associated with the second Paleoindian occupation. The upper paleosol complex is weakly developed, contains no cultural material, and reflects an increase in loess deposition rates. Abundant pedogenic carbonate features indicate dry, warm, alkaline soil conditions. Faunal remains, soil characteristics, and regional palynological studies indicate a warm, dry, open parkland of poplar-willow scrub forest during the deposition of the lower loess, paleosol formation, and Paleoindian occupations. (3) An upper loess unit, up to a meter thick, lacks paleosols, has been leached of carbonate, and has a late Holocene Alfic Cryochrept soil developed on its upper surface. Rapid, coarse-grained loess deposition occurred from about 9000 to 6000 yr B.P. By 4500 yr B.P., slow, fine-grained loess deposition began under boreal forest conditions and continues today.

Marine upwelling occurs when surface currents diverge or are deflected. Deeper water, often nutrient-rich, rises and generates a cascade of biological effects including elevated productivity and a unique assemblage of organisms. Macrofaunal characteristics of upwelling provide key evidence for oxygen-minimum zones, upwelling of cool water, and high productivity and are potentially useful indicators of ancient upwelling. The Upper Triassic Luning Formation in Nevada contains abundant, large ichthyosaurs and was deposited in a back-arc basin that could have experienced upwelling conditions. Luning Formation rocks at West Union Canyon were analyzed for sedimentological, geochemical, and paleontological upwelling indicators. Abundant suspension feeders, lack of corals and calcareous algae, modest total organic carbon and minor element concentrations in deeper marine facies, abundant cosmopolitan molluscs but no taxa restricted to low latitudes, and abundant fecal pellets and clotted fabrics in most facies suggest that upwelling could have influenced Luning deposition. Moderate-scale upwelling likely contributed to eutrophic conditions and ichthyosaur abundance at West Union Canyon. Marine reptiles might have had ties to upwelling areas to provide food, as do modern whales. A relational database containing 817 locality records and 1365 taxon-localities was assembled for ichthyosaurs, plesiosaurs, and mosasaurs. Marine reptile localities were compared with model-predicted upwelling and with upwelling-related lithologies (organic-rich rock, biogenic silica, phosphorite, and glauconite). Marine reptile occurrences intersected predicted upwelling more often than expected by chance for the Upper Cretaceous, Callovian, and Norian stages, and for all of the data together (P = 0.05). For age-restricted data, occurrences of Mosasauridae, Pliosauridae, and Plesiosauria intersected upwelling more often than expected by chance (P = 0.05). Average shortest distances between reptile fossil and upwelling lithology occurrences were smallest (one grid cell adjacent or smaller) for the Pliensbachian and four of five Cretaceous stages. Analytical biases and other aspects of reptile ecology may have affected the results, but overall, upwelling could have influenced marine reptile distribution, particularly for the Upper Cretaceous. Multiple radiations into the high-productivity, top-predator niche over the Mesozoic are suggested by the dominance of different taxa in grid cells containing upwelling lithologies: ichthyosaurs (early Mesozoic), plesiosaurs (middle Mesozoic), and finally mosasaurs (late Mesozoic).

The North Chinese Paleolithic sequence is perplexing in its relative technological simplicity, strikingly different from the known sequences in Mongolia, Siberia and ultimately western Eurasia. The division between North China and western Eurasia, traditionally labeled the Movius Line after the pioneering work of Hallam Movius (1944), has withstood years of scrutiny. The explanation for this phenomenon, however, remains elusive. This dissertation addresses several hypotheses about late Pleistocene lithic technological variability in Northeast Asia on either side of the Movius Line. Of central importance is finding proper placement for Shuidonggou, the only know late Pleistocene locality in North China that contains a well-developed blade industry. Lithic assemblages from two cave sites in the Mongolian Gobi, Tsagaan Agui and Chikhen Agui, and the 1980 excavated collections from Shuidonggou are compared. Comparisons also feature the well-know late Pleistocene materials from Kara Bom, located in southern Siberia. These analyses illustrate that Shuidonggou is linked to the elaboration of initial Upper Paleolithic (IUP) technologies in greater Northeast Asia after 43 ka. A series of theoretical and empirical questions surrounding the Northeast Asian IUP are addressed. I ask whether biogeographic processes, behavioral-ecological processes, or differential use of stone raw materials underlie observed technological disjunctions in Northeast Asia. Three primary conclusions emerge. First, biogeographic processes are implicated in the patterning of lithic technological variability in Northeast Asia. Population growth coupled with periodic opening and closing of dispersal corridors may explain the spread of IUP technologies. Second, mathematical models indicate that the uniform character of IUP core technologies is related to economic advantages inherent in Levallois core geometries. The implication is that the IUP reflects the spread of specific economic adaptations, and not necessarily a particular hominid species. Finally, the failure of prepared core technologies to take hold in East Asian environments cannot be explained by differential use of stone raw materials. Core technologies from one of the study sites illustrate that raw material quality is not an absolute constraint on technological design. Rather, the failure of IUP technologies is linked to population contraction brought on by the extreme conditions of the Last Glacial Maximum (LGM).

Plant-feeding insects are the most species-rich group on the planet today. Models have been proposed to explain this diversity, but few use the fossil record to evaluate hypotheses. I conduct studies in modern systems to examine (1) taphonomic biases in insect preservation and how this may affect our understanding of insect diversity trends through time and (2) patterns of herbivory in modern ecosystems to improve the comparability of fossil and modern datasets. I then use the Cenozoic fossil record to examine the history of ecological associations between insects and plants and how these interactions respond to environmental change. I conducted an actualistic study on the preservation of beetles in Willcox Playa, an ephemeral lake in SE Arizona. I compared the insect death assemblage in shoreline sediments to the living beetle assemblage. The sediments captured 56% of the live-collected beetle families, and 28% of the live-collected beetle genera. The relative abundances of living beetles were not reflected in the death assemblage. Beetle diet, feeding habitat, and size influenced the composition of the death assemblage. Necrophagous, ground-dwelling and smaller beetles were over-represented in the death assemblage. Such biases should be considered in insect paleoepology and in studies of diversity change. Annual variation in herbivory was compared within and between two lowland neotropical forests Costa Rica. Herbivory did not vary significantly within sites between years, but was significantly different: between sites. Modern herbivory data collected with discrete sampling techniques is compartable to herbivory data from fossil forests. Herbivory data from one-time collections of leaf litter are most suitable for comparison with fossil herbivory. I compared herbivory between two Eocene floras and between the Eocene floras and six modern floras. A decline in levels of herbivory corresponds with a decline in temperature from the middle to the late Eocene. Fossil herbivore damage was significantly lower than modern herbivore damage. This pattern may result from taphonomic bias, environmental differences between the fossil and modern sites or evolutionary change.

Forest fire is a keystone ecological process in coniferous forests of southwestern North America. This dissertation examines a fire regime in the Jemez Mountains of northern New Mexico, USA, based on an original data set collected from Monument Canyon Research Natural Area (MCN). First, I examine scale dependence in the fire regime. Statistical descriptors of the fire regime, such as fire frequency and mean fire interval, are scale-dependent. I describe the theory of the event-area (EA) relationship, analogous to the species-area relationship, for events distributed in space and time; the interval-area (IA) relationship, is a related form for fire intervals. The EA and IA also allow estimation of the annual fire frame (AFF), the area within which fire occurs annually on average. The slope of the EA is a metric of spatio-temporal synchrony of events across multiple spatial scales. The second chapter concerns the temporal distribution of fire events. I outline a theory of fire interval probability from first principles in fire ecology and statistics. Fires are conditional events resulting from interaction of multiple contingent factors that must be satisfied for an event to occur. Outcomes of this kind represent a multiplicative process for which a lognormal model is the limiting distribution. I examine the application of this framework to two probability models, the Weibull and lognormal distributions, which can be used to characterize the distribution of fire intervals over time. The final chapter addresses the theory and effects of sample size in fire history. Analytical methods (including composite fire records) are used in fire history to minimize error in inference. I describe a theory of the collector's curve based on accumulation of sets of discrete events and the probability of recording a fire as a function of sample size. I propose a nonlinear regression method for the Monument Canyon data set to correct for differences in sample size among composite fire records. All measures of the fire regime reflected sensitivity to sample size, but these differences can be corrected in part by applying the regression correction, which can increase confidence in quantitative estimates of the fire regime.

No description available.

<p> Eight dissolution caves from the Helderberg Plateau in Schoharie County, New York were studied to investigate unusual sediment packages previously interpreted to be deposits laid down during stagnant ice-cover conditions of the Wisconsin glaciation. The sediment package, consisting of white finely laminated silts and clays are overlain by coarse gravels, in turn overlain by dark silts and clays. Analysis of 63 sediment samples was inconclusive in terms of organic content, but indicated a higher degree of fine-grained calcite material in the white clays than in the overlying units. The caves with the white clays exist only within the footprint of Glacial Lake Schoharie, with lower elevation caves containing a thicker white clay sequence, a measure of the duration of lake cover. The sediment sequence represents glacial rock flour formed under stagnant lake conditions, overlain by outwash deposits emplaced during lake termination, and more recent sediment from soil-loss deposition.</p>

This study presents mineralogic and stable isotopic records generated for piston cores and Ocean Drilling Program holes recovered from intermediate water depths (500 to 2500 meters) near carbonate platforms around the world. Study areas included the Bahamas (western North Atlantic Ocean), the Nicaragua Rise (Caribbean Sea), the Maldives (north equatorial Indian Ocean), and the Queensland Plateau (southwest Pacific Ocean). Mineralogic data includes percent fine aragonite content, percent fine Mg calcite content, pteropod (aragonitic holoplanktonic gastropods) abundance, percent whole pteropods, and for some cores, percent clear pteropods. Carbonate data were interpreted both in terms of carbonate input from the nearby banks and in terms of seafloor dissolution. Planktic foraminiferal $\delta\sp{18}$O records were used as the primary chronostratigraphic tool for all sites. Statistical analyses of four metastable CaCO$\sb3$ dissolution proxies yielded a composite dissolution index (CDI) that displays different dissolution histories for Bahama and Nicaragua Rise sediments over the last 200,000 years. These differences are not predicted by intermediate to deep water nutrient fractionation models (e.g., Boyle, 1988). A good correlation is observed between the Caribbean CDI record (this study) and CaCO$\sb3$ dissolution and benthic $\delta\sp{13}$C records from 4641 meters in the Venezuela Basin, Caribbean Sea (Cofer-Shabica, 1987). It is concluded that during the last 200,000 years, variable cross-equatorial flux of Antarctic Intermediate Water has strongly influenced Caribbean carbon chemistry at water depths greater than 1100 meters. The assumption, therefore, that deep Caribbean sediment cores reliably record nutrient and (CO$\sb3\sp{=}$) variations of average mid-depth Atlantic water may need re-evaluation. Over longer time scales, CaCO$\sb3$ dissolution records from intermediate water depths near the Bahamas, Maldives, and Queensland Plateau are similar to deep-water dissolution records. Dissolution occurred from thermocline to abyssal depths from 500,000 to 300,000 years ago (during the middle Brunhes Chron) and between 1,000,000 and 900,000 years ago revealing that whole-ocean changes in carbonate chemistry have occurred during the Quaternary. Enhanced CaCO$\sb3$ dissolution may be related to decreased Ca$\sp{2+}$ flux to the ocean (decreased glacial weathering) and increased neritic CaCO$\sb3$ production and accumulation during periods of elevated interglacial sea-level highstands.

Examination of Late Pleistocene to recent coastal lithosomes on the east Texas continental shelf can help refine current models aimed at understanding how coastal environments respond to a variety of forcing mechanisms including changes in subsidence rate, sediment supply (climate), and eustasy. High-resolution seismic data, sediment cores, paleontologic data, and radiocarbon ages were examined from bay complexes (fluvial, bay-head delta, middle bay, tidal delta, and barrier shoreline environments), offshore banks, incised valleys, and the Brazos Delta. Within the study area, preservation of these deposits on the shelf has been variable. Coastal lithosomes had a high preservation potential in the eastern portion of the study area (around the Trinity/Sabine incised valley) and a low preservation potential in the western portion of the study area (offshore of Follets Island and the Brazos Delta). Sabine, Heald, Shepard, and Thomas banks, located above and adjacent to the Trinity and Sabine incised fluvial valleys, represent submerged barrier shorelines. The shoreline submergence events have been correlated with flooding surfaces located within the Trinity incised valley. Maps of the paleoenvironments bound by these flooding surfaces indicate that each paleoshoreline submergence event is associated with estuarine environments being shifted tens of kilometers landward. Rising sea level during the Holocene was the forcing mechanism behind these events. Freeport Rocks Bathymetric High, a bank located further to the west, also represents a submerged barrier shoreline. However, this feature was not emplaced during the Holocene transgression; rather, it was deposited during the middle Wisconsin (oxygen isotope stage 3) sea-level highstand. The shoreline associated with the bank was mapped regionally at -15 m +/- 2 m. This suggests sea level was around 15--30 m shallower than what oxygen isotope and coral records indicate for stage 3. A detailed sedimentary and geomorphologic study was undertaken on the Brazos Delta, Texas to better define the facies architecture and controlling processes on wave-dominated delta evolution. The Brazos Delta is primarily composed of fine-grained sediments; prodelta clay composes more than half of the sediment volume. The facies architecture is not representative of the classic strandplain model for wave-dominated deltas due to the strong influence of floods on deltaic evolution.