Earnest D. Paylor

Multispectral Remote Sensing as Stratigraphic and Structural Tool, Wind River Basin and Big Horn Basin Areas, Wyoming

Stratigraphic and structural analyses of the Wind River basin and Big Horn basin areas of central Wyoming are in progress. One result has been the development of an approach to stratigraphic and structural analysis that uses photogeologic and spectral interpretation of multispectral image data to characterize the attitude, thickness, and lithology of strata. New multispectral systems that have only been available since 1982 are used with topographic data to map upper Paleozoic and Mesozoic strata exposed on the southern margin of the Bighorn Mountains. Landsat-acquired thematic mapper (TM) data together with topographic data are used to map lithologic contacts, measure dip and strike, and develop a stratigraphic column that is correlated with conventional surface and subsurface sections. Aircraft-acquired airborne imaging spectrometer (AIS) and thermal infrared multispectral scanner (TIMS) data add mineralogic information to the TM column, including the stratigraphic distribution of quartz, calcite, dolomite, smectite, and gypsum. Results illustrate an approach that has general applicability in other geologic investigations that could benefit from remotely acquired information about areal variations in attitude, sequence, thickness, and lithology of strata exposed at the earths surface. Application of our methods elsewhere is limited primarily by availability of multispectral and topographic data, and quality of bedrock exposures.

Spectral reflectance characterization (0.4 to 2.5 and 8.0 to 12.0 mu m) of Phanerozoic strata, Wind River basin and southern Bighorn Basin areas, Wyoming

ABSTRACT Reflectance spectroscopy, a useful analytical tool available to geologists for over 100 years, has not been widely used in petrologic or stratigraphic studies of sedimentary rocks. We are routinely using laboratory spectral reflectance data covering the 0.4 to 12.0 µm wavelength interval in an investigation of the stratigraphic and structural evolution of the Wind River and Bighorn basin areas, Wyoming. Two types of laboratory spectral reflectance measurements were made on 192 weathered outcrop, bedrock, and core samples: 1) hemispherical reflectance, from 0.4 to 2.5 µm (229 spectra) and 2) biconical reflectance, from 8.0 to 12.0 µm (84 spectra). Results show stratigraphic variations in the spectral properties of sedimentary rocks as encountered in the field. Sample mineralogy was determined using X-ray diffraction and interpretation of spectra. The mineralogy, lithology and stratigraphic distribution of samples are diverse and representative of Phanerozoic siliciclastic and carbonate strata encountered in foreland sedimentary basins. Spectra were sorted into 36 distinct groups, according to the presence or absence of 68 visible and infrared reflectance features. Many spectral features can be assigned to specific molecular phenomena and allow rapid determination of specific minerals. Minerals detectable spectrally include: gypsum, kaolinite, smectite, analcime, goethite, jarosite, calcite, dolomite, and feldspar. Results are contributing to our understanding of the depositional history of the Wind River and Bighorn basin areas; more importantly, results suggest that laboratory, field and remote reflectance spectroscopy have more general geologic applicability in studies of sedimentary rocks. Reflectance spectroscopy can augment conventional laboratory and field methods for petrologic analysis, correlation, interpretation of depositional environments, and construction of facies models.

Preliminary Spectral and Geologic Analysis of Landsat-4 Thematic Mapper Data, Wind River Basin Area, Wyoming

A Landsat-4 Thematic Mapper (TM) image covering the Wind River Basin area, Wyoming, is under evaluation for stratigraphicand structural mapping, and for assessment of spectral and spatialcharacteristics using the six visible, near-infrared, and short-wavelengthinfrared bands.The image (path 36, row 30, ID # 40128-17232) was acquired on November 21, 1982. The data were obtained from the NASA Goddard Space Flight Center in radiometrically and geometrically correctedfullscene magnetic-tape format.To estimate equivalent Lambertian surface spectral reflectance, TMradiance data must first be calibrated to remove atmospheric andinstrumental effects. Reflectance measurements for homogeneousnatural and cultural targets in the scene were acquired during the period October 27-November 3, 1983, about one year after satellite dataacquisition. Scatterplots were prepared of image DN versus reflectancefor these sites. The scatterplots show the TM sensor system response islinear for the conditions of image acquisition and for the mix of terraincover types encountered.Low TM offset and gain settings result in encoded spectral data thatdo not occupy the full dynamic range (256 gray levels) of the TM.Calibration data acquired during the study were used to calculate new gainsand offsets that would improve scanner response for Earth scienceapplications.Analysis demonstrates that principal component images provideuseful structural and stratigraphic information. Principal componentscalculated from the correlation matix result from linear transformationsof ground reflectance. In images prepared from this transform, theseparation of spectral classes is largely independent of systematicatmospheric and instrumental factors.

Spectral stratigraphy: Remote sensing lithostratigraphic procedures for basin analysis, central wyoming examples

Stratigraphic and structural analysis of the Wind River and Bighorn basins of central Wyoming are in progress. One result has been the development of spectral stratigraphy, an approach to stratigraphic analysis that uses photogeologic and spectral interpretation of multispectral image data combined with topographic information to remotely characterize thickness and lithology of strata exposed in sedimentary basins. Thus, spectral stratigraphy is a new tool for use in integrated investigations of the evolution of sedimentary basins.Multispectral sensor systems that have been available since 1982 are used to analyze upper Paleozoic and Mesozoic strata on the southern margin of the Bighorn Mountains and the southern edge of the Bighorn Basin. Thematic Mapper (TM) data are used to develop stratigraphic columns and structural cross sections that are correlated with conventional surface and subsurface sections. Experimental thermal infrared aircraft data facilitate lithofacies/biofacies analysis of the monotonous Cretaceous Cody Shale sequence. Recently developed satellite and aircraft systems provide sufficient spectral resolution to allow for remote determination of the stratigraphic distribution of quartz, calcite, dolomite, gypsum, specific clay species, and other minerals diagnostic of depositional environments. Development of a desktop, computer-based, geologic analysis system that provides for automated stratigraphic interpretation and analysis of combined multispectral image and digital topographic data portends major advances in the application of spectral stratigraphy.Results demonstrate an approach with general applicability in other geologic investigations that could benefit from remotely acquired information about areal variations in sequence, attitude, thickness, and lithology of strata exposed at the Earths surface.

Study of the Reed Dolomite Aided by Remotely Sensed Imagery, Central White-Inyo Range, Easternmost California

Remote sensing methods are of great value in assessing the stratigraphy and geologic structure of inaccessible terrains, especially where lithologic contrasts are marked. In this paper, we show that such techniques can be successfully applied to a massive carbonate unit, the Reed Dolomite, exposed in the Waucoba Mountain, Blanco Mountain, and Mount Barcroft quadrangles of east-central California. Airborne NS-001, satellite Landsat TM, and SPOT panchromatic imagery combined with conventional geologic mapping were employed to demonstrate that observed spectral variations on false-color images were caused by subtle compositional variations of the dolomite. Based on reflectance differences and field investigations, six discrete bedding units were recognized in exposures of th Reed Dolomite. From lower to upper, they are (1) very coarse grained, granular, gray, pisolitic, blocky dolomite; (2) medium-grained, white, oolitic, massive dolomite; (3) fine- to coarse-grained, light-gray, oolitic, massive crystalline dolomite and rare interbedded rusty quartzarenite; (4) medium-fine-grained, cross-stratified, locally ocherous brown, interlayered quartzarenite, tan siltstone, and sandy dolomite; (5) fine-grained, thin-bedded, sparsely oolitic, buff dolomite; and (6) fine-grained, fissile, dull white dolomite. Subunit 4 and underlying subunit 3 appear to interfinger, with subunit 4 representing a more proximal shelf facies. In the southeast corner of the mapped area, subunit 4 is present and subunit 3 is absent, with the situation reversed along the western and northern portions of the range. Subunit 5 thins to a feather edge on the north near the Barcroft Granodiorite. Thickness variations of the different Reed stratigraphic entities in the eastern and northern White-Inyo Range may reflect attenuation caused by granitoid intrusion, as well as original stratigraphic variations. The broad expanse of Reed Dolomite directly northeast of the Sage Hen Flat pluton is due to north-south-trending folds. Details of the White-Inyo anticlinorium are now better resolved in the central portion of the ra ge where previously undetected folds, faults, and homoclinal sections are revealed in false-color imagery of the macroscopically featureless Reed Dolomite. Thickness trends and facies boundaries for the newly recognized subunits trend north-south or north-northeast throughout the study area, locally reflecting the gentle west-northwest continental shelf paleoslope of the passive margin of western North America during latest Precambrian-Early Cambrian. This study is important to petroleum geologists because it demonstrates that detailed stratigraphy and structure can be determined using remote sensing techniques in semiarid regions where massive, indistinct carbonate units crop out. In some cases, no single processing method allows spectral discrimination of all lithostratigraphic entities; furthermore, the spectral characteristics of a specific unit have been shown to vary even within a single image. Hence, our work underscores the site-specific limitations of individual multispectral methods and illustrates why a combination of diverse methods needs to be employed. Finally, geologic lessons learned within the study area may be extrapolated to similar terrains elsewhere within the Basin and Range province. End_Page 1008------------------------------

Basin Analysis Aided by Remote-Sensing Data: Geologic Results in Wind River/Bighorn Basin Area, Wyoming: ABSTRACT

Aircraft and satellite remote-sensing data combined with surface and subsurface geologic and geophysical data have been used to investigate the formation and evolution of Laramide foreland basins in central Wyoming. Quaternary through Holocene geomorphology reveals post-Laramide basin excavation history. Six terrace/pediment surfaces have been recognized in the northern Wind River basin and have been correlated with equivalent surfaces in the Bull Lake and central Wind River basin areas, respectively. Permian through Eocene stratigraphic relationships distinguish late pre-Laramide through Laramide paleogeography. New type sections established in the eastern wind River basin/northern Casper arch area refine lithostratigraphic correlations with: (1) surface sections measured in the southern Bighorn basin and (2) subsurface sections on the southern Casper arch. Structural mapping in the southern Bighorn basin indicates predominantly compressional Laramide deformation. Numerous northeastward-dipping thrust faults that do not appear on published geologic maps have been recognized at the surface and have been confirmed with seismic data. Similar strategies of data acquisition and geologic analysis developed should be applicable in studies of similar foreland basins.

Post-Laramide Uplift and Erosional History of Northern Wind River Basin, Wyoming: ABSTRACT

Landsat Thematic Mapper (TM) multispectral scanner images together with aerial photographs have been used to infer Laramide to Holocene tectonic events along the northern fringe of Wind River basin near Wind River Canyon, Wyoming. TM images reveal the presence of a large system of alluvial fans, terraces, and residual tongue-shaped debris deposits covering an area of 90 mi/sup 2/ at the base of Copper Mountain. The debris system contains predominantly dark metasedimentary clasts. Both Eocene (Wind River and Wagon Bed Formations) and Quaternary deposits are present, and some Eocene gravel has been reworked into the later units. These deposits contrast sharply in brightness and color with rocks in adjacent areas. Detailed topographic analysis of the terraces and fan remnants disclosed an episodic history of post-Wagon Bed (upper to middle Eocene) uplift and pediment cutting. At least 3 principal stages covering a vertical interval possibly as great as 1300 ft have been identified. Soil profiles in Quaternary gravels capping the pediments show increase in maturity consistent with age inferred from topographic elevations. These local erosional stages may record tectonic events of regional significance. Their absolute ages need to be determined.