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Mark E. Gettings

Publications and source records attributed to Mark E. Gettings.

29 records · Page 2Linked to original sources
USGS1999

An interpretation of the 1997 airborne electromagnetic (AEM) survey, Fort Huachuca vicinity, Cochise County, Arizona

In March of 1997, an airborne electromagnetic (AEM) survey of the Fort Huachuca Military Reservation and immediate surrounds was conducted. This survey was sponsored by the U.S. Army and contracted through the Geologic Division of the U.S. Geological Survey (USGS). Data were gathered by Geoterrex-Dighem Ltd. of Ottawa, Canada. The survey aircraft is surrounded by a coil through which a large current pulse is passed. This pulse induces currents in the Earth which are recorded by a set of three mutually perpendicular coils towed in a "bird" about 100 m behind and below the aircraft. The bird also records the Earth's magnetic field. The system samples the Earth response to the electromagnetic pulse about every 16 m along the aircraft flight path. For this survey, the bulk of the flightpaths were spaced about 400 m apart and oriented in a northeast-southwest direction extending from bedrock over the Huachuca Mountains to bedrock over the Tombstone Hills. A preliminary report on the unprocessed data collected in the field was delivered to the U.S. Army by USGS in July 1997 (USGS Open-File Report 97–457). The final data were delivered in March, 1998 by the contractor to USGS and thence to the U.S. Army. The present report represents the final interpretive report from USGS. The objectives of the survey were to: 1) define the structure of the San Pedro basin in the Sierra Vista-Fort Huachuca-Huachuca City area, including the depth and shape of the basin, and to delineate large faults that may be active within the basin fill and therefore important in the hydrologic regime; 2) define near surface and subsurface areas that contain a large volume fraction of silt and clay in the basin fill and which both reduce the volume of available storage for water and reduce the permeability of the aquifer; and 3) to evaluate the use of the time domain electromagnetic method in the southwest desert setting as a means of mapping depth to water.

Arizona↗
USGS1993

Quantifying favorableness for occurrence of a mineral deposit type using fuzzy logic; an example from Arizona

An application of possibility theory from fuzzy logic to the quantification of favorableness for quartz-carbonate vein deposits in the southern Santa Rita Mountains of southeastern Arizona is described. Three necessary but probably not sufficient conditions for the formation of these deposits were defined as the occurrence of carbonate berain rocks within hypabyssal depths, significant fracturing of the rocks, and proximity to a felsic intrusive. The quality of data available to evaluate these conditions is variable over the study area. The possibility of each condition was represented as a fuzzy set enumerated over the area. The intersection of the sets measures the degree of simultaneous occurrence of hte necessary factors and provides a measure of the possibility of deposit occurrence. Using fuzzy set technicques, the effect of one or more fuzzy sets relative to the others in the intersection can be controlled and logical combinations of the sets can be used to impose a time sequential constraint on the necessary conditions. Other necessary conditions, and supplementary conditions such as variable data quality or intensity of exploration can be included in the analysis by their proper representation as fuzzy sets.

Open-File Report↗
USGS1990

Geophysical investigations in Jordan

A number of geophysical investigations have been undertaken in the Hashemite Kingdom of Jordan to provide data for understanding the tectonic framework, the pattern of seismicity, earthquake hazards and geothermal resources of the country. Both the historical seismic record and the observed recent seismicity point to the dominance of the Dead Sea Rift as the main locus of seismic activity but significant branching trends and gaps in the seismicity pattern are also seen. A wide variety of focal plane solutions are observed emphasizing the complex pattern of fault activity in the vicinity of the rift zone. Geophysical investigations directed towards the geothermal assessment of the prominent thermal springs of Zerga Ma'in and Zara are not supportive of the presence of a crustal magmatic source.

Tectonophysics↗
USGS1985

Reconnaissance geologic map of the Wadi Khulab Quadrangle, sheet 16/43 A, Kingdom of Saudi Arabia

The Wadi Khulab quadrangle, bounded by lat 16°30’ and 17°00’ N. and long 42°00’ and 43°30’ E., is one of the southernmost quadrangle of the Kingdom of Saudi Arabia. It is named after Wadi Khulab, which flows westward across the central part of the area. Approximately one-third of the quadrangle, comprising the mapped area, lies within Saudi Arabia; the remainder lies within the Yemen Arab Republic. Delineation of the international boundary should not be considered definitive. From west to east, the physiography of the mapped area consists of a portion of the Tiharmat Asir, or coastal plain, extending from the Jizan quadrangle to the west (Blank and Gettings, 1984), a northwest-trending hill range close to the western border of the quadrangle; a pediplain; and the foothills of the Red Sea escarpment. The top of the escarpment is about 50 km east of the mapped area, in the Yemen Arab Republic. Within Saudi Arabia, the highest elevation in the quadrangle about 77 m above sea level, is found at Tirf in the western range of hills.

Open-File Report↗
USGS1983

An interpretation of gravity and aeromagnetic surveys of the Greater Jiddah area, Kingdom of Saudi Arabia

A gravity survey of the Jiddah area between lat 21°23' and 21°48' N., long 39°03' and 39°20' E., carried out in early 1977, covers an area of 744 km 2 and includes 215 stations, at an average spacing of 1.9 km. The resulting simple Bouguer gravity anomaly map shows a series of four large (7-15 mgal) gravity anomaly highs along a north-trending gravity gradient located immediately west of outcrops of Precambrian rocks. The regional Bouguer gravity anomaly field of the map area decreases eastward at an approximately constant rate of about 1.1 mgal-km-1. Several anomalies suggest northeast-trending, right-lateral strike-slip faulting throughout the area. Interpretation of the Bouguer gravity anomaly map, combined with geologic, aeromagnetic, and paleomagnetic data, leads to an interpretive model in which the gravity gradient marks the boundary zone between Precambrian continental crust to the east and oceanic sea-floor crust overlain by marine sedimentary rocks to the west. The strike-slip faults in the area are probably the landward extension of offshore Red Sea transform faults, and, because they penetrate and offset continental crust, their study may yield useful information about the mechanism of transform faulting. The gravity anomaly highs are interpreted to result from shallow intrusive bodies, probably gabbroic in composition, that are buried a few hundred meters below the surface and that are approximately 2 km thick.

Report↗
USGS1979

Preliminary results of the Sabkhah Hazawza gravity project, Wadi as Sirhan area, Kingdom of Saudi Arabia

One hundred thirty seven new gravity stations at an average station density of one station per 17.5 km2 have been established in a 40 x 60 km area centered on Sabkhah Hazawza in the northwestern part of the Kingdom of Saudi Arabia. A successful tie to existing Arabian American Oil Co. (ARAMCO) gravity data was made and a simple Bouguer gravity anomaly map was compiled during the survey. The map shows a distinct gravity low of about -8 mgal associated with the sabkhah, its minimum displaced to the northeast of the longitudinal axis of the sabkhah. However, the continuation of the gravity anomaly under the basalt field to the northeast suggests that the gravity anomaly is due to an older basin-like structure. If the sabkhah deposits are due to damming of ancient Wadi as Sirhan by basalt flows, then the deposits are probably thin. Preliminary estimates give a maximum thickness of about 270 m for the sedimentary fill causing the gravity anomaly.

Wadi as Sirhan area↗