Floyd F. Sabins

Thermal infrared remote sensing of crude oil slicks

Abstract It is important to develop a remote sensing technique for reliable detection of oil slicks for reasons of both oil exploration and environmental protection. Yet, unambiguous detection has proven an elusive goal. This article presents new thermal infrared spectra of oil slicks made from five different crude oil samples with a wide range of API gravities and compositions. After a brief outgassing phase, all oil slick spectra are quite similar and little affected by thickness, extended exposure to air or sunlight, and even by emulsification with seawater (mousse formation). Thus, oil slicks provide a remarkably unvarying spectral signature as remote sensing targets in the thermal infrared compared to other regions of the spectrum. This spectral signature in the 8–14 μm atmospheric window is flat, with an average reflectance of 4%. Seawater, on the other hand, has a spectrum that varies in reflectance with wavelength in the 8–14 μm window from 0.90 to 3.65%. In addition, we show that sea foam displays a reflectance spectrum quite similar to that of seawater in the 8–14 μm region, because the very high absorption coefficient of water in this wavelength region prevents volume scattering in foam bubbles. This results in a relatively uniform spectral background, against which oil slicks can be detected, based on their different spectral signature. Thus, thermal infrared multispectral remote sensing appears to offer a simple and reliable technique for aircraft or satellite detection of oil slicks.

Geologic Interpretation of Space Shuttle Radar Images of Indonesia

The National Aeronautics and Space Administration (NASA) space shuttle mission in November 1981 acquired images of parts of the earth with a synthetic aperture radar system at a wavelength of 23.5 cm (9.3 in.) and spatial resolution of 38 m (125 ft). This report describes the geologic interpretation of 1:250,000-scale images of Irian Jaya and eastern Kalimantan, Indonesia, where the all-weather capability of radar penetrates the persistent cloud cover. The inclined look direction of radar enhances subtle topographic features that may be the expression of geologic structures. On the Indonesian images, the following terrain categories are recognizable for geologic mapping: carbonate, clastic, volcanic, alluvial and coastal, melange, and metamorphic, as well as undifferentia ed bedrock. Regional and local geologic structures are well expressed on the images. In the Vogelkop region of Irian Jaya, the major tectonic elements (Tamrau Mountains, Sorong fault, Kemum block, Bintuni basin, and Lengguru foldbelt) are readily mapped. On the image of the Sorong fault, geomorphic features (offset drainage, shutterridges, aligned notches) provide clear evidence for left-lateral strike-slip displacement. Several lineaments on the image correlate with previously mapped faults. Other lineaments may be the expression of previously unrecognized faults. On the image of the mainland of Irian Jaya, a belt of metamorphic and melange terrain marks the zone of collision between the Pacific plate and the Australian plate. The high Central Range of Irian Jaya is located south of the metamorphic and melange belt. The generally homoclinal structure of the Central Range is interrupted in the Paniai Lake region by a series of southward directed thrust plates indicated by belts of carbonate terrain (New Guinea Limestone Group) that alternate with belts of clastic terrain (Kembelangan Formation). In the image of eastern Kalimantan, several major foldbelts are clearly expressed. These limited examples of space shuttle radar images demonstrate their value for geologic interpretation of Indonesia. It is recommended that future shuttle missions acquire complete radar coverage of the main islands of Indonesia for use in geologic mapping and energy exploration. Shuttle radar images would also be valuable for other cloud-covered forested regions.

Stratigraphic Relations in Chiricahua and Dos Cabezas Mountains, Arizona

The Chiricahua and Dos Cabezas mountains are typical of the Basin-and-Range Province in southeast Arizona. Well exposed Paleozoic and Mesozoic marine strata overlie a Precambrian basement complex of schist and granite. The 7,600 feet of Paleozoic strata were deposited on a slowly subsiding shelf, beginning in middle(?) or late Cambrian time. Sedimentation was interrupted by an epeirogenic uplift that caused the widespread unconformity between Lower Ordovician and Upper Devonian strata. The pronounced angular discordance between the Paleozoic strata and the Lower Cretaceous beds was caused by a pre-Cretaceous orogeny. Compressive stresses during the post-Comanche--pre-Pliocene orogeny strongly deformed all the strata. The range was uplifted later in the Cenozoic by high-an le faulting. The oldest formation is the Bolsa quartzite (Middle(?) to Upper Cambrian), which unconformably overlies the basement rocks. It is arkosic to quartzose and ranges from 320 to 600 feet in thickness. The El Paso formation (Upper Cambrian-Lower Ordovician) conformably overlies the Bolsa and ranges in thickness from 340 to 715 feet. It consists of dolomite and limestone. The overlying Portal formation (Upper Devonian) is here named for exposures 2½ miles northwest of the village of Portal. The formation ranges from 200 to 342 feet in thickness and consists of the following four members, in ascending order: (1) alternating limestone and shale, (2) black siliceous shale, (3) alternating limestone and shale, (4) bioclastic limestone. The Escabrosa limestone (Lower Mississippian) consists of cherty crinoidal limestone ranging from 630 to 730 feet in thickness. It is overlain by the Paradise formation (Upper Mississippian) which consists of about 150 feet of alternating thin limestone and clastic strata. The Pennsylvanian and Permian systems are represented by the Naco group, composed of about 5,500 feet of limestone and clastic strata. The Naco group is subdivided into the following five formations, in ascending order: Horquilla, Earp, Colina, Scherrer, and Concha. The Horquilla is dominantly limestone and ranges in age from the Morrow to Missouri series. It is conformably overlain by the Earp formation (Missouri to Wolfcamp age) which consists of alternating limestone, sandstone, and shale. The Colina (Wolfcamp to Leonard age) is aphanitic black limestone. The Scherrer (Leonard age) consists of quartzitic sandstone with a basal red siltstone member. The uppermost formation is the Concha limestone (Leonard to Guadalupe? age) which is very fossiliferous and cherty. The dominantly carb nate Naco sequence of southeast Arizona is equivalent to the thinner, dominantly clastic Pennsylvanian-Permian strata of the Colorado Plateau. The Mesozoic era is represented by the Bisbee group of Lower Cretaceous clastic strata. The Glance conglomerate at the base reaches a maximum thickness in excess of 1,000 feet. The overlying 2,500 feet of the Bisbee group is divided into three lithologic units, but no formal names are proposed. The lowest unit is a red siltstone. This is overlain by the thin middle limestone unit, which is probably equivalent to the Mural limestone at Bisbee. The uppermost unit consists of alternating quartzite and siltstone.

GEOLOGY OF THE COCHISE HEAD AND WESTERN PART OF THE VANAR QUADRANGLES, ARIZONA

The area of this report includes parts of the Chiricahua and the Dos Cabezas Mountains which together constitute a typical range in the Mexican Highland section of the Basin and Range province. The Precambrian basement complex consists of the Pinal Schist, with a massive quartzite member, and two granite intrusives: the foliated Sheep Canyon Granite which is a small synkinematic stock, and the nonfoliated Rattlesnake Point Granite which is a large postkinematic intrusive. All these units are cut by Precambrian aplite dikes. The Paleozoic strata have an aggregate thickness in excess of 7600 feet and consist of the following units, in ascending order: Bolsa Quartzite (Middle(?) and Upper Cambrian), El Paso Formation (Upper Cambrian and Lower Ordovician), Portal Formation (Upper Devonian), Escabrosa Limestone (Lower Mississippian), Paradise Formation (Upper Mississippian), and the Naco Group (Pennsylvanian and Permian). The Naco Group is subdivided into the following formations, in ascending order: Horquilla Limestone, Earp Formation. Colina Limestone, Scherrer Formation, and Concha Limestone. The Bisbee Group (Lower Cretaceous) is about 2600 feet thick and includes the Glance Conglomerate at its base. It unconformably overlies the older rocks. The Nipper Formation is here named for mafic volcanic rocks and associated sediments that unconformably overlie the older rocks. The rhyolitic flows of the succeeding Faraway Ranch Formation overlie the Nipper and Bisbee units, and are overlain by the welded tuffs of the Rhyolite Canyon Formation. These volcanic units were formed during the late Cretaceous to late Tertiary interval. All the pre-Rhyolite Canyon formations are cut by Tertiary intrusions of two major types: a light-colored quartz monzonite group and a dark-colored diorite and basalt group. There is evidence for at least five periods of tectonic activity within the area. The Precambrian orogeny, which pre-dated the intrusion of the Rattlesnake Point Granite and the aplite dikes, caused the regional metamorphism and folding of the Pinal Schist. An epeirogenic uplift that began late in early Ordovician time resulted in the disconiormity between the Lower Ordovician strata and the Upper Devonian strata. Uplift and erosion occurred in the late Permian-early Cretaceous interval and supplied the clastic sediments for the Glance Conglomerate. During the major post-Comanche to pre-Pliocene orogeny, strong southerly to southwesterly horizontal compression caused the following tectonic sequence. The autochthonous rocks along the northeast front of the range were overridden from the southwest by the first thrust sheet. Strike-slip displacement along the Emigrant fault cut the autochthonous block and the overlying thrust sheet, which was separated into the Fort Bowie plate and the Wood Mountain plate. The Fort Bowie plate was later folded to form the Marble Quarry syncline and was truncated by the younger Fort Apache reverse fault. Finally, the Whitetail plate overrode the Fort Apache fault block. During the Basin and Range orogeny (Pliocene?) vertical displacement along high-angle faults adjacent to the range uplifted the mountains relative to the valleys on either side.

Grains of Detrital, Secondary, and Primary Dolomite from Cretaceous Strata of the Western Interior

Three genetic types of dolomite grains occur in Cretaceous sandstones of the Western Interior and Alaska. They are: (1) Detrital—clastic fragments eroded from dolomite rocks in the sediment-source terrain. These are well-rounded polycrystalline aggregates with relict internal textures inherited from the source rocks. (2) Secondary—formed after deposition of the enclosing sediment. These are small euhedral rhombs that replaced calcite cement in lenticular marine sandstones. (3) Primary—formed within the depositional basin prior to final settling-down and burial of the sediment. These are single rhombic crystals abraded to various degrees of roundness and sorted to the size of associated clastic sand grains. The fabric relationships are of the depositional type, with no evidence of relict internal structures. This ––––eliminates a possible secondary origin. A detrital origin is eliminated by the absence of inherited textures and by the distribution patterns, for primary-dolomite grains are restricted to marine sandstones. Within these sandstones, the primary-dolomite grains are most abundant in the basinward portions. The grains are widely distributed in marine Cretaceous sandstones throughout the Western Interior, regardless of variations in lithology of sediment-source terrains. The recognition and interpretation of primary-dolomite grains is the major contribution of this paper.

Thermal Infrared Imagery and Its Application to Structural Mapping in Southern California

Thermal infrared imagery is obtained by airborne scanning devices that detect thermal radiation from the earth9s surface and record it as an image in which bright tones represent relatively warm temperatures. Scanners sensitive to wavelengths between 8 and 14 microns span the radiant power peak of the earth at 9.7 microns and coincide with an atmospheric “window.” An example of 8 to 14 micron nighttime infrared imagery from the Imperial Valley, California, is interpreted and compared with aerial photographs of the same area. In this monotonous-appearing desert terrain, the imagery exhibits greater contrast and geologic detail than the photography. On the imagery, deformed Tertiary sedimentary bedrock (relatively cool) is distinguished from Holocene windblown sand cover (relatively warm). Of especial geologic interest is a faulted plunging anticline in flat terrain. It is obscure both on aerial photographs and to a ground observer. On nighttime infrared imagery, however, the fold is clearly shown by the outcrop configuration of the individual siltstone and sandstone strata comprising the structure. Apparently the radiometric temperature differences between strata are sufficient to outline the fold on the imagery. The obscure expression of the fold on aerial photographs may be due to insufficient contrast in light reflectance between the different strata.

Symmetry, Stratigraphy, and Petrography of Cyclic Cretaceous Deposits in San Juan Basin

Late Cretaceous strata of the San Juan basin consist of cyclically interstratified non-marine, nearshore marine, and offshore marine clastic sediments which were deposited both during marine transgressions and regressions. Thickness of the transgressive and regressive parts of these cyclic sequences varies, permitting subdivision into two types of cycles: symmetrical and asymmetrical. In symmetrical cycles the thickness of transgressive and regressive parts are nearly equal; in asymmetrical cycles the transgressive sandstone is absent. The Hosta-Point Lookout wedge is an example of a symmetrical cycle. At its base the transgressive marine Hosta Sandstone overlies continental strata of the Crevasse Canyon Formation. The Hosta Sandstone grades upward into the offshore marine Satan Shale. The Satan Shale marks the midpoint of the cycle and the maximum marine inundation; it grades upward into the regressive marine Point Lookout Sandstone. The Point Lookout is overlain by the continental Menefee Formation. Southwestward, toward the former shoreline, the Satan Shale pinches out and the transgressive and regressive sandstones merge into a single massive sandstone, which still farther southwestward grades into continental strata. The Mulatto-Dalton cycle is asymmetrical for it lacks a basal transgressive sandstone. Instead, the offshore Mulatto Shale directly overlies the continental Dilco Coal with only scattered marine sand lenses at the contact. The Mulatto Shale grades southwestward (toward former shoreline) and upward into the regressive marine Dalton Sandstone which in turn grades southwestward into, and is overlain by, continental deposits of the Crevasse Canyon Formation. Petrography is closely related to the sandstone depositional environments as follows. Regressive sandstone type: Upward increase in maximum and median grain diameter; upward decrease in abundance of primary dolomite grains. These vertical changes reflect progressive shallowing of the basin during regression. Transgressive sandstone type: Upward decrease in maximum and median grain diameter; upward increase in abundance of primary dolomite grains. These vertical changes reflect progressive deepening during transgression. Non-marine sandstone type: Wide range of grain sizes; primary dolomite grains absent; abundant carbonaceous material; higher proportion of non-quartz detritus. Petrography and the cycle concept are useful for recognizing and solving correlation problems.

Seasat radar image of San Andreas Fault, California

On a Seasat radar image (23.5-cm wavelength) of the Durmid Hills in southern California, the San Andreas fault is expressed as a prominent southeast-trending tonal lineament that is bright on the southwest side and dark on the northeast side. Field investigation established that the bright signature corresponds to outcrops of the Borrego Formation, which weathers to a rough surface. The dark signature corresponds to the Lake Cahuilla sand and silt deposits which are smooth at the wavelength of the Seasat radar. These signatures and field characteristics agree with calculations of the smooth and rough radar criteria. On Landsat and Skylab images of the Durmid Hills, the Borrego and Lake Cahuilla surfaces have similar bright tones and the San Andreas fault is not detectable On a side-looking airborne radar image (0.86-cm wavelength), both the Borrego and Lake Cahuilla surfaces appear rough, which results in bright signatures on both sides of the San Andreas fault. Because of this lack of roughness contrast, the fault cannot be distinguished on the aircraft image acquired at a short radar wavelength. The wavelength of the Seasat radar system is well suited for mapping Durmid Hills geologic features that are obscure on the other remote sensing images evaluated in this report.

Geologic Interpretation of Radar and Space Imagery of California: ABSTRACT

Side-looking airborne radar (SLAR) imagery in California is interpreted in terms of geologic structure and rock type. Field checks and comparison with published geologic maps indicate some revisions of existing maps. In particular, linears on the radar imagery point to previously unmapped faults. In outcrops where surface texture is related to bedrock lithology, the radar signature may indicate rock type. The unmanned Earth Resources Technology Satellite (ERTS) telemeters multispectral-scanner imagery that is reconstituted into reflected-infrared-color imagery. With respect to radar imagery, the ERTS imagery has poorer spatial resolution and smaller scale; nevertheless, useful regional patterns may be interpreted. Repetition of ERTS imagery on an 18-day cycle should enable us to determine the season for obtaining maximum geologic information. End_of_Article - Last_Page 802------------

Geologic Applications of Remote Sensing: ABSTRACT

For optimum geologic application of remote sensing, the user should understand the advantages, limitations, and characteristics of the various types of imagery. Selection of the optimum sensor or combination of sensors will depend upon these factors plus the nature of the terrain, geology, and the problem at hand. Newer types of films and image processing have greatly expanded the geologic potential of conventional black and white aerial photography. Infrared color film and multiband photography extend the sensitivity range and provide greater spectral discrimination. These techniques can enhance subtle variations in soil, vegetation, End_Page 362------------------------------ and moisture content which may be geologically significant. The newer photographic methods from earth orbiting satellites provide broad regional coverage that may reveal major geologic trends and features not apparent on conventional photography. Airborne infrared scanners image the thermal radiation patterns of the earths surface. Geologic applications that have been demonstrated for this new technology are (1) mapping faults, (2) distinguishing different rock types, (3) recognition of subtle structural patterns, (4) mapping near-surface groundwater distribution, (5) monitoring of volcanic areas, (6) detection of geothermal resources, and (7) monitoring of arctic sea ice. Radar is a day or night technique that penetrates fog or clouds to provide strips of imagery with broad regional coverage and a uniform oblique illumination of the terrain. Radar has generated imagery of areas that hitherto have not been photographed from the air because of persistent cloud and fog cover such as in eastern Panama. The major geologic advantage of radar imagery is the enhancement of faults, fractures, and lineaments that may be obscure on other forms of imagery. The polarization capability of radar can discriminate subtle surface textural differences. End_of_Article - Last_Page 363------------