Geology topics

M. Allison Stegner

Publications and source records attributed to M. Allison Stegner.

6 recordsLinked to original sources

USGS2026

Southeastern Utah Federal lands science needs survey

Evidence-based scientific information can help support defensible decision making in the management of public lands. This report sought to identify current (2024–25) Federal agency research needs in southeastern Utah and to synthesize common management challenges and questions across jurisdictional boundaries. We implemented a science needs assessment focused on lands managed by the Bureau of Land Management (BLM), U.S. Department of Agriculture Forest Service (FS), and National Park Service (NPS) in southeastern Utah—the area delineated by BLM’s Canyon Country District Office, portions of the FS Manti-La Sal National Forest, and Southeast Utah Group NPS units. U.S. Geological Survey (USGS) researchers met with and surveyed BLM, NPS, and FS staff in 2024 and 2025 to understand their science needs and preferred modes of information delivery. The USGS’s approach may be unrepresentative in terms of which topic areas were addressed, but the responses nevertheless highlight challenges and high-priority research areas that could contribute positively to agency decision making. Common management challenges and areas where additional research could be beneficial to land managers include the effects of climate change, recreation effects and visitor behavior, hydrology and hydrologic changes due to anthropogenic pressures, and the capacity for inventory and monitoring across essentially all resource types. Research on site-specific restoration techniques and their outcomes was also a common theme. In this report we discuss ways in which researchers can increase the extent to which their work could be actionable for resource managers and provide suggestions for potential priority research areas for the study region.

Utah↗

USGS2026

Vulnerability of different Colorado Plateau land types to drivers of change

Public lands are challenged by a range of pressures—changing climate, increasing visitation, resource extraction—and their effects can span spatial scales, often crossing land management jurisdictional boundaries. Research approaches which explicitly span jurisdictions can support strategies to contend with regional pressures. We assess management-relevant drivers of change—aridification, livestock grazing, invasive species, surface disturbance, and fire—across a patchwork of land management units and agencies on the Colorado Plateau, focusing on southeastern Utah, USA. We use vulnerability analysis, first evaluating exposure to drivers across the landscape, then quantifying sensitivity to each driver across different land types, defined by mapped Ecological Site Groups, a system for classifying landscapes according to physical factors including climate, soils, and topographic setting. We address the questions: 1) how are drivers spatially distributed across the study region; and, 2) based on exposure and sensitivity, are certain land types more vulnerable to these drivers? We find that the study region has high exposure and sensitivity—and thus high vulnerability—to aridification and grazing, but low exposure and vulnerability to other drivers. Although more sensitive land types were not generally more exposed, identifying which areas are most sensitive can guide adaptive measures, like where new uses or disturbances would be least harmful and which areas could be prioritized for restoration. The method we demonstrate is a flexible tool for assessing landscape-scale impacts, is built on nationally available datasets, and can be tailored to different datasets and sensitivity metrics.

Utah↗

USGS2024

Palaeontological signatures of the Anthropocene are distinct from those of previous epochs

The “Great Acceleration” beginning in the mid-20th century provides the causal mechanism of the Anthropocene, which has been proposed as a new epoch of geological time beginning in 1952 CE. Here we identify key parameters and their diagnostic palaeontological signals of the Anthropocene, including the rapid breakdown of discrete biogeographical ranges for marine and terrestrial species, rapid changes to ecologies resulting from climate change and ecological degradation, the spread of exotic foodstuffs beyond their ecological range, and the accumulation of reconfigured forest materials such as medium density fibreboard (MDF) all being symptoms of the Great Acceleration. We show: 1) how Anthropocene successions in North America, South America, Africa, Oceania, Europe, and Asia can be correlated using palaeontological signatures of highly invasive species and changes to ecologies that demonstrate the growing interconnectivity of human systems; 2) how the unique depositional settings of landfills may concentrate the remains of organisms far beyond their geographical range of environmental tolerance; and 3) how a range of settings may preserve a long-lived, unique palaeontological record within post-mid-20th century deposits. Collectively these changes provide a global palaeontological signature that is distinct from all past records of deep-time biotic change, including those of the Holocene.

Earth Science Reviews↗

USGS2023

Witnessing history: Comparison of a century of sedimentary and written records in a California protected area

We use a combination of proxy records from a high-resolution analysis of sediments from Searsville Lake and adjacent Upper Lake Marsh and historical records to document over one and a half centuries of vegetation and socio-ecological change—relating to logging, agricultural land use change, dam construction, chemical applications, recreation, and other drivers—on the San Francisco Peninsula. A relatively open vegetation with minimal oak ( Quercus ) and coast redwood ( Sequoia sempervirens ) in the late 1850s reflects widespread logging and grazing during the nineteenth century. Forest and woodland expansion occurred in the early twentieth century, with forests composed of coast redwood and oak, among other taxa, as both logging and grazing declined. Invasive species include those associated with pasturage ( Rume x , Plantago ), landscape disturbance ( Urtica , Amaranthaceae), planting for wood production and wind barriers ( Eucalyptus ), and agriculture. Agricultural species, including wheat, rye, and corn, were more common in the early twentieth century than subsequently. Wetland and aquatic pollen and fungal spores document a complex hydrological history, often associated with fluctuating water levels, application of algaecides, raising of Searsville Dam, and construction of a levee. By pairing the paleoecological and historical records of both lakes, we have been able to reconstruct the previously undocumented impacts of socio-ecological influences on this drainage, all of which overprinted known climate changes. Recognizing the ecological manifestations of these impacts puts into perspective the extent to which people have interacted with and transformed the environment in the transition into the Anthropocene.

California↗

USGS2023

The Searsville Lake Site (California, USA) as a candidate Global boundary Stratotype Section and Point for the Anthropocene series

Cores from Searsville Lake within Stanford University’s Jasper Ridge Biological Preserve, California, USA, are examined to identify a potential GSSP for the Anthropocene: core JRBP2018-VC01B (944.5 cm-long) and tightly correlated JRBP2018-VC01A (852.5 cm-long). Spanning from 1900 CE ± 3 years to 2018 CE, a secure chronology resolved to the sub-annual level allows detailed exploration of the Holocene-Anthropocene transition. We identify the primary GSSP marker as first appearance of 239,240 Pu (372–374 cm) in JRBP2018-VC01B and designate the GSSP depth as the distinct boundary between wet and dry season at 366 cm (6 cm above the first sample containing 239,240 Pu) and corresponding to October-December 1948 CE. This is consistent with a lag of 1–2 years between ejection of 239,240 Pu into the atmosphere and deposition. Auxiliary markers include: first appearance of 137 Cs in 1958; late 20th-century decreases in δ 15 N; late 20th-century elevation in SCPs, Hg, Pb, and other heavy metals; and changes in abundance and presence of ostracod, algae, rotifer and protozoan microfossils. Fossil pollen document anthropogenic landscape changes related to logging and agriculture. As part of a major university, the Searsville site has long been used for research and education, serves users locally to internationally, and is protected yet accessible for future studies and communication about the Anthropocene.

California↗

USGS2022

Planetary-scale change to the biosphere signalled by global species translocations can be used to identify the Anthropocene

We examine three distinctive biostratigraphic signatures associated with: hunting and gathering, landscape domestication, and globalisation. All three signatures have significant fossil records of regional importance that can be correlated inter-regionally and help describe the developing pattern of human expansion and appropriation of resources. While none have individual first or last appearances that provide a globally isochronous marker, all three signatures overlap stratigraphically, in that they are part of a continuum of change, with complex regional patterns. Here we show that during the later stages of globalisation, late 19th to 20th century records of species translocations can be used to build an interconnected web of palaeontological correlation with decadal or sub-decadal precision that dovetails with other stratigraphic markers for the Anthropocene. This palaeontological web is also a proxy for accelerating species extinction and of a state shift in the biosphere in the 20th century.

Palaeontology↗