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Geology topics

Arthur Grantz

Publications and source records attributed to Arthur Grantz.

65 records · Page 4Linked to original sources
USGS1960

An aeromagnetic reconnaissance of the Cook Inlet area, Alaska

Forty-two east-west aeromagnetic lines were flown across the Cook Inlet-Susitna Lowland between Chelatna Lake and Seldovia at a flight altitude of approximately 2,500 feet. The lines traverse all or part of five Mesozoic tectonic elements that dominate the structure of the Cook Inlet area. Each of these tectonic elements, the Alaska Range geosyncline, the Talkeetna geanticline, the Matanuska geosyncline, the Seldovia geanticline, and the Chugach Mountains geosyncline, has a characteristic magnetic pattern. The aeromagnetic data, compiled as total intensity aeromagnetic profiles, show several significant features which are consistent with the structural grain of the area. A two-dimensional anomaly was observed near the east edge of the area on all but the southernmost profiles, where it becomes obscure. Geologic evidence suggests that this feature, the Knik Arm anomaly, is produced by plutonic rocks that have been intruded along the Seldovia geanticline. Southeast of this anomaly the profiles are almost flat. This flatness indicates that magnetic rocks are deeply buried in this area, which is underlain by slate and graywacke deposited in the Chugach Mountains geosyncline.

Alaska↗
USGS1954

Magnetite deposits at Tuxedni Bay, Alaska

The magnetite deposits on an island in Tuxedni Bay occur in contact-metamorphosed volcanic and sedimentary rocks near their contact with a quartz diorite batholith which underlies large areas of the adjacent Aleutian Range. The deposits are pyrometasomatic in origin and are localized along northeast-trending fractures. The eastern deposit is a low-grade disseminated deposit occurring in hornfels. The western deposit occurs as a massive lens of magnetite and garnet with a marble hanging wall and a hornfels footwall. The tenor of mineral rock in the western deposit may average 75 percent of magnetite. The deposit is lenticular and can be followed along strike for 55 feet in outcrop and, where concealed beneath a cover of soil and vegetation, can be followed for an additional 55 feet with a dip needle. Where exposed in a sea cliff the deposit is 30 to 35 feet thick.

Alaska↗