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Laura E. Strickland

Publications and source records attributed to Laura E. Strickland.

14 recordsLinked to original sources
USGS2024

Shallow lake, strong shake: Record of seismically triggered lacustrine sedimentation from the 1959 M7.3 Hebgen Lake earthquake within Henrys Lake, Idaho

We investigate a shallow lake basin for evidence of a large historic intraplate earthquake in western North America. Henrys Lake, Idaho is an atypical candidate for a lacustrine paleoseismic study given its shallow depth (~7 m) and low relief (≤2° slopes ). Here, we test the earthquake-recording capacity of this basin type by showing sedimentological evidence of the 1959 M7.3 Hebgen Lake earthquake within sediment cores, using anthropogenically produced 137 Cs activity to constrain timing. In addition to expanding the morphologic range of basins targeted for lacustrine paleoseismic studies, this work has implications for sediment response in dam-enhanced basins. Lack of sedimentological evidence for other earthquakes coupled with radiocarbon chronology reveals that the 1959 event is the only clearly recorded earthquake within Henrys Lake since the mid-Holocene. Henrys Lake offers a proxy for paleo-earthquake signatures within similar lacustrine environments and underscores the importance of further paleoseismic studies in the region.

Idaho↗
USGS2024

Neotectonic mapping of Puerto Rico

Puerto Rico is part of the Puerto Rico-Virgin Islands microplate, along the Caribbean–North American plate boundary between the Puerto Rico trench subduction zone and the Muertos Trough incipient subduction zone. Despite recent seismicity and geodetically constrained deformation of ~3 mm/yr of left-lateral shear across the island, Quaternary fault locations remain largely uncertain. Preservation of recent faulting in the landscape is masked by distributed faulting, high weathering rates of the tropical climate, steep topography, frequent landsliding, and extensive agriculture and urbanization along coastlines and river valleys. We present remote neotectonic mapping of historical aerial imagery from the 1930s-60s and <1-m lidar topography, integrated with field observations, to create an updated active fault map of Puerto Rico. We focus on faults that offset younger geomorphic surfaces, with ages estimated by geologic mapping, OSL and radiocarbon dating, and morphologic interpretations. We present new evidence for Quaternary activity on seven faults, including the South Lajas, Salinas, Punta Montalva, Great Southern Puerto Rico, Cerro Goden, Parguera, and San Marcos faults. We find that active faulting occurs preferentially along the southern and western coasts and does not always spatially coincide with preexisting bedrock faults, possibly reflecting partial reactivation of older faults in the modern strain field.

Puerto Rico↗
USGS2024

Plant macrofossil data for 48-0 ka in the USGS North American Packrat Midden Database, version 5.0

Plant macrofossils from packrat ( Neotoma spp.) middens provide direct evidence of past vegetation changes in arid regions of North America. Here we describe the newest version (version 5.0) of the U.S. Geological Survey (USGS) North American Packrat Midden Database. The database contains published and contributed data from 3,331 midden samples collected in southwest Canada, the western United States, and northern Mexico, with samples ranging in age from 48 ka to the present. The database includes original midden-sample macrofossil counts and relative-abundance data along with a standardized relative-abundance scheme that makes it easier to compare macrofossil data across midden-sample sites. In addition to the midden-sample data, this version of the midden database includes calibrated radiocarbon ( 14 C) ages for the midden samples and plant functional type (PFT) assignments for the midden taxa. We also provide World Wildlife Fund ecoregion assignments and climate and bioclimate data for each midden-sample site location. The data are provided in tabular (.xlsx), comma-separated values (.csv), and relational database (.mdb) files.

Scientific Data↗
USGS2022

Holocene paleohydrology from alpine lake sediment, Emerald Lake, Wasatch Plateau of central Utah, USA

Holocene sediments at Emerald Lake in central Utah (3090 m asl) document the paleohydroclimatic history of the western Upper Colorado River headwater region. Multi-proxy analyses of sediment composition, mineralogy, and stable isotopes of carbonate (δ 18 O and δ 13 C) show changes in effective moisture for the past ca. 10,000 years at millennial to decadal timescales. Emerald Lake originated as a shallow, closed-basin cirque pond during the Early Holocene. By ca. 7000 cal yr BP, higher lake levels and carbonate δ 18 O values indicate rising effective moisture and higher proportions of summer precipitation continued at least until ca. 5500 cal yr BP when a landslide entered the lake margin. Between ca. 4500 and 2400 cal yr BP dry conditions at Emerald Lake envelop the timing of the ‘Late Holocene Dry Period’ identified at lower elevations. For the past ca. 2500 years, Emerald Lake δ 18 O values were relatively low, indicating wetter conditions and higher snow input (compared to rain), except for dry periods at ca. 2000 cal yr BP and during the Medieval Climate Anomaly at ca. 1000 and ca. 500 cal yr BP. Results provide a long-term perspective on precipitation extremes that influence regional water supplies from a snow-dominated catchment typical of the predominant source region for the Upper Colorado River.

Utah↗
USGS2021

Assessing the uncertainties in climatic estimates based on vegetation assemblages: Examples from modern vegetation assemblages in the American Southwest

Assemblages of fossil plant remains have been widely used to reconstruct past climatic conditions, usually through the application of methods that involve either finding vegetation analogues on the modern landscape (and using the modern associated climatic values as the basis for an estimate) or using the modern climatic ranges of individual taxa in an assemblage to determine the range of a given climate variable that would allow these plant taxa to live together. Although these approaches are relatively straightforward, it is difficult to assess the uncertainties associated with each approach, particularly in regard to their application to plant macrofossil assemblages. To explore the uncertainty that may arise from inaccuracy and imprecision in climate reconstructions and from ecological considerations we used variants of both approaches to estimate climate from two data sets of modern vegetation assemblages from the southwestern United States: (1) 1752 gridded “virtual plant assemblages” based on plant range maps that provide uniform spatial coverage of the presence or absence of major woody plant taxa across the study area; and (2) 43 modern packrat ( Neotoma spp.) midden presence-absence assemblages that are similar to fossil midden assemblages. By comparing observed and estimated climate values, we evaluated the quality of the climate estimates, identified sources of uncertainty, and characterized the nature and magnitude of the effects of these uncertainties on the climate estimates. Uncertainties in estimating climate from vegetation assemblages arise because any given plant taxon (or assemblage) must have the resiliency to survive a range of climatic variability, and because of the strong intercorrelations among climatic variables in the modern climate data. Additional sources of uncertainty in climate estimates from plant assemblages include: (1) the modern climate and plant distribution data that are selected as the basis for estimation; (2) the particular quantitative approach that is used to estimate climate; (3) the sufficiency of the number of taxa in the analysis for providing an unbiased representation of the vegetation community as it existed for each time period in the analysis; and, (4) the location of the assemblage on the climatic and environmental gradients in the calibration data set for each climate variable under consideration. We conclude that vegetation assemblages can provide valid and reproducible estimates of climatic variables and that the primary trends and mapped patterns in the observed climate data can be reconstructed from such estimates. However, many factors may affect the quality of an estimate from a given plant assemblage, including aspects of data selection, data adequacy, methodologies, and the location of the assemblage site relative to gradients in the base climate data. It is particularly difficult to accurately estimate extreme values in the observed climate data, because estimated values from either end of an observed climate gradient necessarily “move toward the middle” of the gradient. In addition, the interval chosen to represent modern climate (here we used 1961 to 1990) may have a large impact on the size of the estimated difference between modern and past climate at a given site.

Arizona, California, Colorado, Nevada, New Mexico,↗
USGS2018

A North American Hydroclimate Synthesis (NAHS) of the Common Era

This study presents a synthesis of century-scale hydroclimate variations in North America for the Common Era (last 2000 years) using new age models of previously published multiple proxy-based paleoclimate data. This North American Hydroclimate Synthesis (NAHS) examines regional hydroclimate patterns and related environmental indicators, including vegetation, lake water elevation, stream flow and runoff, cave drip rates, biological productivity, assemblages of living organisms, and salinity. Centennial-scale hydroclimate anomalies are obtained by iteratively sampling the proxy data on each of thousands of age model realizations and determining the fractions of possible time series indicating that the century-smoothed data was anomalously wet or dry relative to the 100 BCE to 1900 CE mean. Results suggest regionally asynchronous wet and dry periods over multidecadal to centennial timescales and frequent periods of extended regional drought. Most sites indicate drying during previously documented multicentennial periods of warmer Northern Hemisphere temperatures, particularly in the western U.S., central U.S., and Canada. Two widespread droughts were documented by the NAHS: from 50 BCE to 450 CE and from 800 to 1100 CE. Major hydroclimate reorganizations occurred out of sync with Northern Hemisphere temperature variations and widespread wet and dry anomalies occurred during both warm and cool periods. We present a broad assessment of paleoclimate relationships that highlights the potential influences of internal variability and external forcing and supports a prominent role for Pacific and Atlantic Ocean dynamics on century-scale continental hydroclimate.

Global and Planetary Change↗
USGS2017

A high-elevation, multi-proxy biotic and environmental record of MIS 6-4 from the Ziegler Reservoir fossil site, Snowmass Village, Colorado, USA

In North America, terrestrial records of biodiversity and climate change that span Marine Oxygen Isotope Stage (MIS) 5 are rare. Where found, they provide insight into how the coupling of the ocean&ndash;atmosphere system is manifested in biotic and environmental records and how the biosphere responds to climate change. In 2010&ndash;2011, construction at Ziegler Reservoir near Snowmass Village, Colorado (USA) revealed a nearly continuous, lacustrine/wetland sedimentary sequence that preserved evidence of past plant communities between ~ 140 and 55 ka, including all of MIS 5. At an elevation of 2705 m, the Ziegler Reservoir fossil site also contained thousands of well-preserved bones of late Pleistocene megafauna, including mastodons, mammoths, ground sloths, horses, camels, deer, bison, black bear, coyotes, and bighorn sheep. In addition, the site contained more than 26,000 bones from at least 30 species of small animals including salamanders, otters, muskrats, minks, rabbits, beavers, frogs, lizards, snakes, fish, and birds. The combination of macro- and micro-vertebrates, invertebrates, terrestrial and aquatic plant macrofossils, a detailed pollen record, and a robust, directly dated stratigraphic framework shows that high-elevation ecosystems in the Rocky Mountains of Colorado are climatically sensitive and varied dramatically throughout MIS 5.

Colorado↗
USGS2017

Last interglacial plant macrofossils and climates from Ziegler Reservoir, Snowmass Village, Colorado, USA

Ninety plant macrofossil taxa from the Ziegler Reservoir fossil site near Snowmass Village, Colorado, record environmental changes at high elevation (2705 m asl) in the Rocky Mountains during the Last Interglacial Period. Present-day vegetation is aspen forest ( Populus tremuloides ) intermixed with species of higher ( Picea , Abies ) and lower ( Artemisia , Quercus ) elevations. Stratigraphic units 4&ndash;13 contain montane forest taxa found near the site today and several species that today generally live at lower elevations within ( Abies concolor , Lycopus americanus ) and outside Colorado ( Najas flexilis ). These data suggest near-modern climatic conditions, with slightly warmer summer and winter temperatures. This montane forest period was succeeded by a shorter treeless interval (Unit 14) representing colder and/or drier conditions. In units 15&ndash;16, conifer trees reoccur but deciduous and herb taxa are lacking, suggesting a return to warmer conditions, although cooler than during the earlier forest period. Comparison of these inferred paleoclimatic changes with the site's geochronologic framework indicates that the lower interval of sustained warmth correlates with late MIS 6&ndash;early 5b (~ 138&ndash;94 ka), the cold interval with MIS 5b (~ 94&ndash;87 ka), and the uppermost cool assemblages with MIS 5a (~ 87&ndash;77 ka).

Colorado↗
USGS2015

Atlas of relations between climatic parameters and distributions of important trees and shrubs in North America: Revisions for all taxa from the United States and Canada and new taxa from the western United States

This is the seventh volume in an atlas series that explores the relations between the geographic distributions of woody plant species and climatic variables in North America. A 25-kilometer (km) equal-area grid of modern climatic and bioclimatic variables was constructed from weather data. The geographic distributions of selected tree and shrub species were digitized, and the presence or absence of each species was determined for each point on the 25-km grid, thus providing a basis for comparing climatic data and species' distributions. The relations between climate and plant distributions are presented in graphical and tabular form. The results of this effort are intended primarily for use in biogeographic, ecologic, paleoclimatic, and global-change research. This volume of the atlas provides numerous changes, updates, and enhancements from previous volumes. Its geographic coverage is now restricted to Canada and the continental United States, and the source and time period of the climatic data have changed. New variables were added, including monthly values for temperature and precipitation, and measures of interannual variability. The distribution maps for all previously published species were redigitized, some distribution maps were revised, and 148 new species were added from the arid and semiarid western United States. The graphical displays were expanded to illustrate the new climatic variables, and the data tables were modified to provide more detail on the population distributions of plant taxa relative to climatic variables.

North America↗
USGS2012

Quantitative estimation of climatic parameters from vegetation data in North America by the mutual climatic range technique

The mutual climatic range (MCR) technique is perhaps the most widely used method for estimating past climatic parameters from fossil assemblages, largely because it can be conducted on a simple list of the taxa present in an assemblage. When applied to plant macrofossil data, this unweighted approach (MCR un ) will frequently identify a large range for a given climatic parameter where the species in an assemblage can theoretically live together. To narrow this range, we devised a new weighted approach (MCR wt ) that employs information from the modern relations between climatic parameters and plant distributions to lessen the influence of the "tails" of the distributions of the climatic data associated with the taxa in an assemblage. To assess the performance of the MCR approaches, we applied them to a set of modern climatic data and plant distributions on a 25-km grid for North America, and compared observed and estimated climatic values for each grid point. In general, MCR wt was superior to MCR un in providing smaller anomalies, less bias, and better correlations between observed and estimated values. However, by the same measures, the results of Modern Analog Technique (MAT) approaches were superior to MCR wt . Although this might be reason to favor MAT approaches, they are based on assumptions that may not be valid for paleoclimatic reconstructions, including that: 1) the absence of a taxon from a fossil sample is meaningful, 2) plant associations were largely unaffected by past changes in either levels of atmospheric carbon dioxide or in the seasonal distributions of solar radiation, and 3) plant associations of the past are adequately represented on the modern landscape. To illustrate the application of these MCR and MAT approaches to paleoclimatic reconstructions, we applied them to a Pleistocene paleobotanical assemblage from the western United States. From our examinations of the estimates of modern and past climates from vegetation assemblages, we conclude that the MCR un technique provides reliable and unbiased estimates of the ranges of possible climatic conditions that can reasonably be associated with these assemblages. The application of MCR wt and MAT approaches can further constrain these estimates and may provide a systematic way to assess uncertainty. The data sets required for MCR analyses in North America are provided in a parallel publication.

Quaternary Science Reviews↗
USGS2012

Atlas of relations between climatic parameters and distributions of important trees and shrubs in North America&mdash; Modern data for climatic estimation from vegetation inventories

Vegetation inventories (plant taxa present in a vegetation assemblage at a given site) can be used to estimate climatic parameters based on the identification of the range of a given parameter where all taxa in an assemblage overlap ("Mutual Climatic Range"). For the reconstruction of past climates from fossil or subfossil plant assemblages, we assembled the data necessary for such analyses for 530 woody plant taxa and eight climatic parameters in North America. Here we present examples of how these data can be used to obtain paleoclimatic estimates from botanical data in a straightforward, simple, and robust fashion. We also include matrices of climate parameter versus occurrence or nonoccurrence of the individual taxa. These relations are depicted graphically as histograms of the population distributions of the occurrences of a given taxon plotted against a given climatic parameter. This provides a new method for quantification of paleoclimatic parameters from fossil plant assemblages.

Professional Paper↗
USGS2006

Atlas of relations between climatic parameters and distributions of important trees and shrubs in North America - Alaska species and ecoregions

Climate is the primary factor in controlling the continental-scale distribution of plant species, although the relations between climatic parameters and species' ranges is only now beginning to be quantified. Preceding volumes of this atlas explored the continental-scale relations between climatic parameters and the distributions of woody plant species across all of the continent of North America. This volume presents similar information for important woody species, groups of species, and ecoregions in more detail for the State of Alaska. For these analyses, we constructed a 25-kilometer equal-area grid of modern climatic and bioclimatic parameters for North America from instrumental weather records. We obtained a digital representation of the geographic distribution of each species or ecoregion, either from a published source or by digitizing the published distributions ourselves. The presence or absence of each species or ecoregion was then determined for each point on the 25-kilometer grid, thus providing a basis for comparison of the climatic data with the geographic distribution of each species or ecoregion. The relations between climate and these distributions are presented in graphical and tabular form.

Alaska↗
USGS2003

Quaternary vegetation and climate change in the western United States: Developments, perspectives, and prospects

This chapter explores the strengths and shortcomings of the major sources of data on Quaternary vegetation and climate change and discusses the use of models as a means to explore past and potential future environmental changes. The flora and major vegetation types of the western United States are present for several million years. Ongoing changes in atmospheric chemistry , climate, and human activities may lead to major vegetation changes over the coming decades to centuries. The combination of observations from the paleoenvironmental record, modern ecological studies, and modeling now permit assessments of the magnitude of potential future changes in the context of natural variability. They also provide opportunities for hypothesis testing and identification of the processes driving past changes in vegetation and climate. Understanding the dynamics of paleoenvironmental change can contribute to current conservation and natural resource management efforts and will help conservation and natural resource managers anticipate the potential rate, magnitude, and complexity of future vegetation change.

western United States↗