Following the rivers: historical reconstruction of California voles Microtus californicus (Rodentia: Cricetidae) in the deserts of eastern California

The California vole, Microtus californicus, restricted to habitat patches where water is available nearly year-round, is a remnant of the mesic history of the southern Great Basin and Mojave deserts of eastern California. The history of voles in this region is a model for species-edge population dynamics through periods of climatic change. We sampled voles from the eastern deserts of California and examined variation in the mitochondrial cytb gene, three nuclear intron regions, and across 12 nuclear microsatellite markers. Samples are allocated to two mitochondrial clades: one associated with southern California and the other with central and northern California. The limited mtDNA structure largely recovers the geographical distribution, replicated by both nuclear introns and microsatellites. The most remote population, Microtus californicus scirpensis at Tecopa near Death Valley, was the most distinct. This population shares microsatellite alleles with both mtDNA clades, and both its northern clade nuclear introns and southern clade mtDNA sequences support a hybrid origin for this endangered population. The overall patterns support two major invasions into the desert through an ancient system of riparian corridors along streams and lake margins during the latter part of the Pleistocene followed by local in situ divergence subsequent to late Pleistocene and Holocene drying events. Changes in current water resource use could easily remove California voles from parts of the desert landscape

1967-2016, celebrating 50 years of geoscience in the mid-continent guidebook for the 50th annual meeting of the Geological Society of America, North-Central Section, April 18-19, 2016

Field Trip 1: The Quaternary geology of the southern Chicago metropolitan area; the Chicago Outlet, morainic systems, glacial chronology, and Kankakee Torrent; Field Trip 2: Fluorite deposits within the Illinois-Kentucky fluorspar district and how they relate to the Hicks Dome cryptoexplosive feature, Hardin County, Illinois; Field Trip 3: Quaternary geology of the upper Sangamon River basin; glacial, postglacial, and postsettlement history; Field Trip 4: Provenance, age, and depositional mechanisms of the Grover Gravel; evidence for multiple erosion cycles, volcanic eruptions, and early glaciations; Field Trip 9: Project-based field trips to the Starved Rock area for geoscience educators, northern IllinoisOpe

Workshop on Meteorites From Cold and Hot Deserts

The current workshop was organized to address the following points: (1) definition of differences between meteorites from Antarctica, hot deserts, and modern falls; (2) discussion of the causes of these differences; (3) implications of possible different parent populations, infall rates, weathering processes, etc.; (4) collection, curation, and distribution of meteorites; and (5) planning and coordination of future meteorite searches

Paleobiogeography of the North American Late Cretaceous Western Interior Seaway: the impact of abiotic vs. biotic factors on macroevolutionary patterns of marine vertebrates and invertebrates

My research investigates the relationship between ecology, evolution, and the environment in the fossil record. I hypothesize that abiotic environmental factors (e.g., climate, sea-level, ocean chemistry, and paleogeography) play a greater role in speciation, extinction, and distribution patterns than biotic factors (e.g., competition, mutualism). The effects of these factors can be observed in the fossil record as changes in species distributions, range sizes, and niche dimensions through time. Using GIS, paleoenvironmental reconstruction, and ecological niche modeling (ENM), I quantitatively investigated hypotheses of the relative influence of abiotic vs. biotic factors on macroevolution in three main studies of marine taxa from the Late Cretaceous Western Interior Seaway (WIS) of North America. The Late Cretaceous was a period of prolonged extreme and equable warmth; thus, this research has potential implications for species biology and biogeography in a projected future warmer world. The first study examined the influence of biotic interactions on patterns of extinction by competitive exclusion in marine vertebrates. Results indicated that competitive replacement was not a mechanism mediating extinctions. Instead other factors, such as environmental changes, likely controlled extinction patterns. The second study investigated the effect of large range size on survivorship and invasion potential in marine mollusks. No relationship between large range size and extinction resistance was recovered, however, endemic species with small range sizes were more likely to become invasive. These results suggest that some biogeographic "rules" (e.g., large range size confers extinction resistance and increased invasion potential) may not prevail under conditions of prolonged and equable global warmth. The last part of my research focused on improving methods for the application of ENM in the fossil record (paleo-ENM). In order to use ENM in the fossil record, detailed environmental layers must be reconstructed from sedimentological and geochemical proxies. Additionally, paleo-ENM requires high-resolution stratigraphic correlations of fossil-bearing formations and collection of large species' occurrence datasets that represent the full temporal and spatial extent of the species modeled. In order to produce high fidelity models, a standardized framework for paleoenvironmental reconstruction is required. Best practices are outlined for paleoenvironmental reconstruction, in addition to the contextual framework and important considerations necessary to appropriately apply paleo-ENM

Interpretative Challenges and Opportunities in Oxygen and Strontium Isotope Compositions of Bivalve Shells.

Oxygen and strontium from biogenic carbonates (mostly bivalves) were used to evaluate paleoenvironmental interpretations on the basis of modern analogs along the North American east coast and to offer chronostratigraphic, paleoenvironmental, and diagenetic constraints to Neogene sequences from Southern McMurdo Sound, Antarctica. These are relevant pursuits in light of imminent climatic changes, which heighten the need for reliable paleoenvironmental interpretations and for data from climate–sensitive regions. In Vineyard Sound, Massachusetts, U.S.A., d18O from several coexisting shallow marine taxa and well–constrained environmental parameters were used to test the extent to which the known local annual variation of these parameters was represented in the shell carbonate. This relation was explored through the construction of time series from bivalve d18O versus shell distance profiles and the calculation of growth rates and isotopic fractionation factors. It was discovered that the marine temperature range recorded in the biogenic carbonate extended to lower temperatures than expected and was, in its entirety, better represented not by a single taxon but by the concurrent use of multiple taxa. Modeling of bivalve d18O of modern shallow marine environments along the North American east coast showed that large salinity ranges complicate environmental interpretations. However, modeled clams showed that d18O seasonal variability can discriminate between tropical and temperate shallow water marine climates. Higher variability characterizes the winter of tropical zones while the opposite is true for temperate regions. 87Sr/86Sr and Sr concentration of unaltered calcite bivalves from ANDRILL’s core AND–2A produced reliable ages and confirm contrasting marine climate conditions across the Middle Miocene of Southern McMurdo Sound, Antarctica. In contrast, seemingly unaltered aragonite shells invariably produced older than expected ages. Additional analyses of the aragonite shells and 87Sr/86Sr compositions of pore water were carried out to reconcile these results. d18O and Sr concentrations of pore water and aragonites suggested that the anomalous ages are likely the result of early diagenetic alteration, even in the absence of mineralogical change.Ph.D.GeologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/77880/1/mariacm_1.pd

From Sea To Lake: The Depositional History Of Saint Albans Bay, Vt, Usa

Sediment accumulated in lakes stores valuable information about past environments and paleoclimatological conditions. Cores previously obtained from Saint Albans Bay, located in the Northeast Arm of Lake Champlain, VT record the transition from the Champlain Sea to Lake Champlain. Belrose (2015) documented the presence of a peat horizon separating the sediments of the Champlain Sea from those of Lake Champlain. Initially, this layer was thought to comprise the transition from the marine environment of the Champlain Sea to a freshwater wetland. However, based on the results from this study, the transition between marine and freshwater conditions is thought to be represented by an erosional unconformity, indicative of a lowstand at the end of the Champlain Sea period. For this study, five additional cores were collected from Saint Albans Bay along a transect following the long axis of the bay moving into progressively deeper water. These cores better constrain the spatial extent, thickness and age variability of the peat layer within the bay and allow us to better understand the environmental conditions that preceded the period of peat deposition. In each of the cores there is evidence of sediment reworking in the uppermost Champlain Sea sediments, indicated by the presence of coarse-grained sediment, which is suggestive of a lowstand at the end of the Champlain Sea period before the inception of Lake Champlain. This coarse-grained layer is immediately overlain by a thick peat horizon. The widespread occurrence of the peat layer points to a large wetland that occupied the entire inner portion of Saint Albans Bay, and lake level ~ 9 m lower than at present during the Early Holocene. Based on radiocarbon dating, this paleo-wetland existed in Saint Albans Bay from ~ 9,600-8,400 yr BP. The development of this wetland complex is time transgressive, reflecting rapidly increasing lake level during the Early Holocene. This hypothesis is supported by the basal peat radiocarbon dates, as well as by the composition of plant macrofossils recovered from the peat horizons. The shift from peat deposition to fine-grained, low organic content lacustrine sedimentation is believed to have occurred at ~8.6-8.4 ka and is likely the result of continued isostatically driven lake level rise coupled with a changing climate. Although it was not its primary focus, this study also seeks to address the variations in sediment composition in the Lake Champlain sections of the cores. Evidence from the Lake Champlain record in Saint Albans Bay indicates that there were notable fluctuations in sedimentation, which were likely linked to both climatic variations and a change in the morphology of the bay. The rebound in productivity from ~8-5 ka is likely the result of warmer conditions during the Hypsithermal period. An increase in terrigenous sedimentation during this same time suggests a change in the morphology of the bay in which the Mill River delta migrated towards the inner bay. Initially, the cooler conditions of the Neoglacial are reflected in Saint Albans Bay by a decrease in organic matter content from ~5-3 ka. During the latter part of the Neoglacial (~3-1 ka), increases in organic matter content and detrital input point to enhanced productivity in response to increased precipitation and runoff from the watershed. The most recently deposited sediments in Saint Albans Bay bear out the legacy of anthropogenic nutrient enrichment of the bay in the form of increased algal productivity

Geoarcheology in North-Central Texas: A Framework for Archeological Investigation, and Cultural Resource Management in the Fort Worth Highway District

This document represents an examination of geoarcheological issues affecting a nine– county area in and around Fort Worth, Texas. The study area includes Tarrant, Wise, Jack, Parker, Palo Pinto, Erath, Hood, Somervell, and Johnson Counties (Figure1–1), which collectively make up the Fort Worth District, a regional administrative entity of the Texas Department of Transportation (TxDOT). This study represents the second phase of a district– focused geoarcheological program being implemented at TxDOT. A similar study of the Houston District was published previously (Abbott 2001a), and studies of other districts are planned. The current study is intended to familiarize archeologists, planners, and transportation professionals working in the region with relevant geoarcheological issues, thus serving as a resource for those involved in prospection, assessment, and interpretation of prehistoric archeological sites. Readers of the previous Houston study are warned that the overall organization of the document and some of the text may seem familiar, as a certain degree of self–plagarism was practiced, particularly in the discussion of geomorphic and soil processes in Part II. Although the focus of investigation is on the nine counties making up the Fort Worth District, many of the issues addressed are equally applicable to adjacent areas of north–central Texas