Gravity and magnetic investigations along the Alaska Highway

Oldham, C. H. G.

doi:10.4095/8708

Cited by 2 publications

(2 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The association o.f negative anomalies with intrusive masses of silicic rock has been commonly observed [Bott, 1953;Oldham, 1958; Woollard, Ostenso, Thiel, and Bonini, 1960] and this explanation of the gravity minimum must be considered.…”

Section: Using the Relation Z • •-• Xma•logl 4k P Xma / G•-i Derived Bymentioning

confidence: 97%

Geophysical investigations in the Colorado Delta Region

Kovach¹,

Allen²,

Press³

1962

J. Geophys. Res.

View full text Add to dashboard Cite

Abstract. The combined approach of gravity and seismic refraction techniques was used to determine depths of the Cenozoic section and fault patterns of the Colorado delta region. Bouguer gravity anomalies range from --10 to --88 mgal with respect to the International Ellipsoid, and the trend of isogal contours is northwesterly. In the center of the basin, depths to basement estimated from gravity data are less than known minimum depths determined from seismic refraction profiles. This discrepancy suggests density complexities within the deeper parts of the stratigraphic section, an interpretation that is supported by sparse measurements from well samples; local isostatic compensation may also contribute to the discrepancy but is not thought to be the major cause. Measured seismic velocities ranged from 5650 to 20,000 ft/sec, and several consistent velocity zones were widespread above the pre-Tertiary basement; indicated depths to basement varied from 2200 feet to at lea,• 15,400 feet, the greatest depth being near the international border. Many members of the San Andreas fault system are well delineated by gravity and seismic data, including the Elsinore and San Jacinto faults and a fault beneath the Sand Hills. Of these, the San Jacinto fault appears to be the most continuous through the delta region, but all appear to be en echelon to the trend of the San Andreas fault system as a whole.

show abstract

Section: Using the Relation Z • •-• Xma•logl 4k P Xma / G•-i Derived Bymentioning

confidence: 97%

Geophysical investigations in the Colorado Delta Region

Kovach¹,

Allen²,

Press³

1962

J. Geophys. Res.

View full text Add to dashboard Cite

show abstract

“…Reconnaissance gravity data based primarily on shoreline measurements (Barnes et al 1972(Barnes et al , 1975Barnes 1977) Brew (1990). eastern Alaska; data for the adjacent parts of Canada are limited to a railroad traverse from Skagway to Bennett lake (Barnes et al 1972) and a few highway measurements north of Atlin (Oldham 1958). Gravity information for all the mountainous terrain is from D. F. Barnes (unpublished data).…”

Section: Introductionmentioning

confidence: 99%

A northern Cordilleran ocean–continent transect: Sitka Sound, Alaska, to Atlin Lake, British Columbia

Brew¹,

Karl²,

Barnes³

et al. 1991

Can. J. Earth Sci.

View full text Add to dashboard Cite

The 155 km wide, 310 km long Sitka Sound – Atlin Lake continent–ocean transect includes almost all the geologic, geophysical, and geotectonic elements of the Canadian Cordillera. It crosses the Chugach, Wrangellia, Alexander, Stikine, and Cache Creek terranes, the Gravina and Laberge overlap assemblages, intrusive and metamorphic belts, and neotectonic faults that bound major blocks. Linear belts of magnetic highs are associated with Jurassic and Cretaceous granitic belts in Wrangellia and the western and central parts of the Alexander terrane and with the granitic rocks of the Coast plutonic–metamorphic complex (CPMC). The Border Ranges fault may be expressed at depth on either side of the Peril Strait fault. An enigmatic northeast-trending gradient in the CPMC and adjacent rocks separates a regional magnetic low to the northwest from a 300 nT high field to the southeast. The Bouguer gravity field decreases in broad steps from Pacific crust high values to lows at the international boundary, with pronounced gradients at the east edge of Chugach terrane and west edge of of CPMC. It indicates that the crust thickens from about 20 to 40 km from southwest to northeast. Ultramafic bodies in the Chugach, Alexander, and Wrangellia terranes and Gravina assemblage underlie local highs. Most of the accumulated seismic strain is released by large earthquakes on the Fairweather – Queen Charlotte Islands plate-margin fault, but the northern part of the Glacier Bay region, the Denali fault zone, and the Coast Mountains also have significant seismicity. Part of the Glacier Bay region is being uplifted at a high rate. Most of these features are related to the joining of (i) Wrangellia to Alexander terrane (Carboniferous), (ii) Stikine to Cache Creek terrane (Early Jurassic), (iii) Alexander terrane and Gravina assemblage to Stikine (Late Cretaceous), and (iv) Chugach to Wrangellia and Alexander terrane (Late Cretaceous or Paleogene).

show abstract

Gravity and magnetic investigations along the Alaska Highway

Cited by 2 publications

References 0 publications

Geophysical investigations in the Colorado Delta Region

Geophysical investigations in the Colorado Delta Region

A northern Cordilleran ocean–continent transect: Sitka Sound, Alaska, to Atlin Lake, British Columbia

Contact Info

Product

Resources

About