ALLISON JACOBEL

Advisor: Louisa Bradtmiller
Senior Honors Thesis: 2011

Southern Hemisphere Climate Variability During the Last Interglacial: ice rafted debris and the Patagonian Ice Sheet

While incoming solar insolation at 65°N is thought to play a primary role in pacing glacial-interglacial climate cycles, paleoclimate records from the mid and high southern latitudes are required to verify this hypothesis and determine the mechanism(s) transferring climatic changes around the globe.  Here we present an 80 kyr ocean sediment record of ice rafted debris (IRD), foraminiferal abundance, oxygen isotopes and changes in clay mineralogy from the Chilean Margin during the last interglacial.  We find that increases in IRD and negative oxygen isotope values correspond, with a constant lag, to minima in Southern Hemisphere insolation and are not related to changes in the westerly winds.

KAREN JACKSON

Advisor: Kelly MacGregor
Senior Honors Thesis: 2011

Sediment Transport and Flow Dynamics of Indianhead Reservoir, St Croix River, MN/WI: Implications for downstream native mussel habitat

Dams impound water and trap sediment in their reservoirs, changing local flow regimes and starving downstream reaches of bed sediment.  The region downstream of St. Croix Falls dam has experienced a fining of bed sediment over the past 20 years, along with a decrease in the juvenile mussel population. I hypothesize that sand from the Indianhead Reservoir breaches the dam due to increased infilling. Reservoir flow dynamics are lacustrine at low discharges, while channel morphology and bed sediment distribution in the reservoir is fluvial. Suspended sediment concentrations and particle settling velocities suggest sand is capable of transport during annual floods. 

BRADLEY ANDRES

Advisor: Kristi Curry Rogers
Senior Honors Thesis: 2010

Tracking Bone Taphonomy at the Microstructural Scale: A Cretaceous Case Study

My study focused on microscopic destruction of marine vertebrate bones (n=56) derived from a conglomerate at the base of the Turonian Carlile Shale exposed in eastern South Dakota.  Three key questions were addressed: 1) What features characterize the microscopic taphonomy of the Carlile Shale? 2) Do trabecular and compact bone tissues exhibit comparable levels of microstructural degradation? And 3) Do bioerosive features typically co-occur with physical taphonomic modification in compact bone tissue?  My results highlight the significance of microorganismal decay on the degradation and preservation of vertebrate bones in the fossil record. 

JACQUELINE KUTVIRT

Advisor: Kelly MacGregor
Senior Honors Thesis: 2011

Holocene Fire History and Paleoenvironmental Change in Eastern Glacier National Park, Montana, USA

Fire activity, used as a proxy for aridity and paleoecological change, is important to quantify in the northern Rocky Mountains, a region sensitive to climate change. Our goal is to illuminate climate variability the high alpine environment of Glacier National Park, Montana. Using abundance of charcoal in lake sediments, we create a 7600-year long record of fires in Swiftcurrent Lake basin, located in the Many Glacier region. Overall fire activity is low compared to lower elevation records; fire frequency increased three times background levels between 3600 and 2800 years ago, coincident with a period of aridity in the western U.S. 

EMMA LOCATELLI

Advisor: Louisa Bradtmiller
Senior Honors Thesis: 2011

Vegetation History of the Late Holocene in East Glacier National Park, Montana: A Paleoenvironmental Study

The apparent temporal and spatial variability of both the Medieval Warm Period (MWP; 1000-1200 AD) and Little Ice Age (LIA; 1400-1800 AD) suggests that more research is necessary to determine how these climate anomalies were expressed in the northern hemisphere. This study uses a record of pollen accumulated in alpine lake sediment from Swiftcurrent Lake (SWF) in Glacier National Park to examine the response of vegetation to climate changes during the MWP and the LIA. We find that the region surrounding SWF was likely drier and warmer than present during the MWP, and became cooler and wetter during the LIA. 

 Read the project on Digital Commons

DEIRDRE RATIGAN

Advisor: Raymond Rogers
Senior Honors Thesis: 2011

Using Experimental Taphonomy to Replicate Bone Alteration in the Judith River Formation (Upper Cretaceous, Montana)

This thesis examines how vertebrate microfossils become polished. Microfossils from fluvial and lacustrine microfossil bonebeds in the Judith River Formation of north-central Montana were compared, and unpolished small bone fragments of various ages were abraded in a vibrating rock tumbler with sediment from the Judith River Formation. The results are consistent with the premise that floodplain-hosted microfossils were reworked by contemporaneous rivers and polished through sediment abrasion. Tumbling results show that sediments can impart a polish on fossil bone within hours. Quaternary bone divested of organic content polished most quickly, followed by recrystallized Cretaceous bone. Fresh bone polished most slowly.

Read the project on Digital Commons