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Surficial geologic mapping
—multipurpose databases for surface process, climate history, and other applications

Project overview

Surficial geologic maps are essential for addressing pressing scientific and social issues such as understanding and predicting the effects of climate change and human impacts on landscapes, ecosystem function, and earth-science hazards. Surficial geologic maps, particularly when combined with physical property databases, are multipurpose and are needed to evaluate diverse landscape attributes. Landscape processes are tightly coupled to climatic processes and therefore sedimentary sequences record information about past climate changes, which in turn can be used to infer possible consequences of future climate variability. Physical properties of sediments strongly influence the availability of water and nutrients for biota, making this information vital for predicting ecosystem function, health, and recovery.

Despite their importance, surficial geologic maps at all scales are widely lacking in much of the United States. This project will work closely with other USGS projects, researchers in academia, and State Geological Surveys to: (1) expedite publication of completed surficial geologic maps at all scales from local to National; (2) prepare maps and develop physical-property databases of surficial materials, primarily at a scale of 1:100,000; (3) develop and test remote sensing techniques for extending surficial geology and physical properties into unmapped areas; (4) investigate surface processes to evaluate landscape dynamics and to improve the geologic map content; (5) produce maps of faults, landslides, debris flow deposits, and sediment transport through space and time for the last 15,000 years, including comparisons with climatic, vegetation, and land-use changes; and (6) plan for and guide the structure of digital databases that will comprise a living National surficial geologic database.

Capabilities

Because the desert landscape is a complex mosaic it requires integrated study of its many parts: vegetation, wildlife, soils, and climate. Furthermore, these integrated parts undergo coordinated change with time, such as vegetation responding to increasingly wet climate conditions. The desert landscape project maintains a correspondingly diverse staff and close associations with other studies in order to shed light on the complex, interwoven landscape issues.

Project staff capabilities	Partnering capabilities
Project management Database management GIS science and spatial databases Quantitative and qualitative geomorphology Soil science Tectonic geomorphology Soil moisture modeling Remote sensing science Climate history Geochronology Paleoseismology Hillslope geomorphology	Vegetation mapping Biotic soil crusts mapping Soil compaction modeling Palynology Groundwater recharge modeling Herpetology Botany Fluvial geomorphology

Cooperative studies that further broaden our capabilities are underway with:

Goals

This project will document ecosystem process, climate history, hazard susceptibility, and surface process information in the desert southwest by preparing a series of multipurpose surficial geologic map databases with integrated material properties data. The maps and associated databases will contain information on the temporal and spatial patterns of surface processes, and include material properties with which the databases can be used to model specific landscape applications. The maps will be applied landscape management problems, including guiding decisions about landscape changes likely in future climates.
Initial efforts for mapping will be focused in the largely unmapped arid southwest. The area stretching from Los Angeles to Las Vegas will serve as a prototype for developing methods and nomenclature. We will build on surficial geologic mapping and ecosystem studies underway by several USGS projects, State Geological Surveys, the Desert Research Institute, and several academia research programs. This location also allows for the study of climate gradients from the coast, across the coastal mountain ranges to desert, and ending on the Colorado Plateau. Study of the climate gradients will tie high-resolution Holocene climate records in the Santa Barbara Basin to deserts and plateaus, mainly by study of climate records from scattered locations throughout the deserts (such as springs) and by study of variable sediment fluxes in a variety of geomorphic environments through the Holocene. The study of sediment flux and process as a function of space and time will allow evaluation of the sensitivity of the desert landscape to climate change.
The project will have two closely tied emphases, each of which utilizes geologic map databases. One will focus on major research issues in Quaternary geology of the southwest U.S. in the broad categories of: (1) geomorphic and soil development processes, (2) climate history and landscape changes associated with climate change, (3) soil hydrology as it impacts ecosystem function and groundwater recharge, (4) material properties as they relate to such processes as soil compaction, enhanced earthquake shaking, and erosion, and (5) changes in Holocene materials and processes over time as a function of climate and tectonics. The second will be on preparing surficial geologic maps and physical property databases with the goal of completing and continually improving a National surficial geologic database. We will consult with Quaternary researchers to standardize map content, mapping methods, and information content. After developing these standards we will experiment with database storage in a flexible format so that reclassification and delivery of data can be quickly accomplished by users of the National surficial geologic database.

Principal Tasks

National Surficial Geologic Map Database

Preparing and maintaining a modern National database of surficial geology is key to making the surficial geology maps available to all users and providing for their numerous applications. This task seeks to (1) develop a National database, (2) update maps in that database, and (3) add new maps and functionality.

1. Quaternary geology of the eastern U.S. was compiled at a scale of 1:2.5 million as a digital database. In order to prepare a functional national surficial geology database, the western part will be completed and merged with the east, and released as an on-line database.
2. The Quaternary National Atlas consists of surficial geology presented in Atlas sheets at a standard scale (1:1M) and with a standard classification of map units. Atlas sheets currently are completed for the eastern 60% of the conterminous U.S., two in the Rocky Mountains, and one on the west coast. A few more sheets will be produced, and geology presented in all sheets will be digitized and modernized to update the database at 1:1M scale.
3. New map databases of all scales will be added to the national surficial geology database to continually upgrade it.

Surficial Geologic Mapping

Surficial geologic maps inform about the properties of the materials with which we most often interact, and the potentially hazardous processes by which these materials are transported. Information is needed on all scales from site descriptions to regional databases in order to make informed decisions. This task seeks to develop surficial geologic maps at several scales in the American southwest.
The most efficient method to meet the needs of local land managers and for producing modern small-scale surficial geologic maps is to incorporate detailed surficial geologic maps into intermediate-scale mapping to prepare and publish a series of intermediate-scale surficial geologic maps. In concert with the process of publishing existing maps and conducting intermediate-scale mapping, physical properties of surficial materials will be acquired by a combination of field tests, samples analyzed in laboratories, and carefully tested models for extrapolating the properties. The physical properties databases will be released as an integral part of the surficial geology databases. Physical properties are essential for such uses as modeling wind and water erosion and susceptibility to strong ground shaking, for understanding soil moisture and infiltration and runoff properties, and for predicting response to human impacts.

Surface Process Investigations

Most surface process studies in arid environments thus far have focused on relatively simple depositional systems such as fluvial perennial rivers, alluvial fans, eolian dune fields, and playas. As a result, these environments can be confidently described on geologic maps. The processes operating within mingled environments such as the alluvial fringes of dune fields and playa margins represent deposits in a sizable fraction of the desert environment and must be understood in order to identify meaningful map units and to assign appropriate material properties. In addition, hillslope processes must be understood to learn the role of climate and biota on sediment transport from hillslopes to alluvial fans. Although hillslopes serve as sediment sources for alluvial fans, little is known about the relationship between hillslope attributes and the processes of sediment transport.
We will seek excellent examples to characterize the surface process systems, quantify interactions among different surface processes, and examine ecological roles in the zone of interactions. Where possible, we will document changes in the processes in these systems as a function of time, and draw conclusions about the role of climate and biota in the systems. From these studies we will draw conclusions about the importance of mingled environments and hillslopes in terms of ecological function and effects of climate change on the systems.

Remote Sensing Research

Remote sensing data will be essential for rapidly extrapolating surficial geologic mapping and physical properties into unmapped areas. The bulk of the research will be to identify the best approaches for quantifying physical properties of surface materials. Our approach will be to develop several remote sensing data sets, such as multifrequency radar, thermal, and hyperspectral, to describe material properties. The effectiveness of the data will be evaluated in areas that have ground-truthing already completed and new studies underway.

Climate History

A complete understanding of landscape processes requires an understanding of how they are driven by climate change and variability on different time scales. This task establishes changes in desert landscape process as a function of climate variation since the last glacial period (approximately the last 15,000 years).
Variations of sediment flux since the last glacial are established and correlated with climate records. A series of records will be pieced together for the region extending from the Santa Barbara channel, through the Transverse Ranges and the Mojave Desert, to the Colorado Plateau. Principal targets for climate and sediment flux records in the deserts are springs, selected playas that may undergo little eolian deflation, and sites of long-term sediment accumulation such as aggrading alluvial fans.

Ecological Processes

Many facets of the ecology of the arid southwest, whose plants and animals depend principally on water availability, can be understood with just a few kinds of information. One is surface materials, which are mapped through understandings of geomorphic and soil-forming processes; attributes of the materials in turn control available soil moisture and nutrients for plants. Thus, maps of soil surface materials can be used to develop many derivative maps that are essential for ecological process models. We are demonstrating how effectively surficial geologic maps provide information on ecological processes at Canyonlands National Park.

Earthquake Hazard Applications

Surficial geologic maps contain abundant data that are vital for understanding physical response to earthquake shaking and economic exposure associated with destructive shaking. The maps present information on depositional process, age, soil development, and thickness of materials. These data, when coupled with texture and information on underlying materials, can increase the quality of predictions for economic losses from seismic events and for predictions of intense ground shaking for actual events. We are developing and testing demonstration products for these applications that are expected to show the improved results when incorporating surficial geologic map information into earthquake hazard assessments.