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Bedrock Data from Western Cape Cod, Massachusetts (WELLSITE shapefile, Geographic, NAD27)

Metadata Updated: October 26, 2023

Cores collected from recent drilling in western Cape Cod, Massachusetts provide insight into the topography and petrology of the underlying bedrock. Cores from 64 drill sites spread over a approximately 140 km2 study area produced samples of granitoids (31), orthogneisses (20), basalts/diabases (4), amphibolites (3), felsic mylonites (2), and dolomitic rock (2). Granitoid composition ranges from granite to tonalite and quartz diorite, but it is dominated by two-feldspar granites. Hydrothermal alteration is common in nearly all cores as evidenced by the secondary growth of chlorite and epidote. Granitoids resemble rocks of the Dedham and Fall River plutons (Wones and Goldsmith, 1991). Gneisses generally contain the mineral assemblage K-feldspar+plagioclase+quartz+/-biotite+/- chlorite+/-muscovite+/-sphene+/-epidote+oxides. Amphibolites contain the assemblage hornblende+plagioclase+quartz+biotite+epidote+/-chlorite+/-sphen+/-K-feldspar+/-sericite+ oxides. Peak metamorphic grade based on mineral assemblages is estimated at lower amphibolite facies. X-ray powder diffraction of unmetamorphosed dolomitic cores shows presence of layered silicates (clays), plagioclase, and possible magnesite. Contours of the bedrock surface show locally irregular topography suggesting erosion by glacial scour. Lithologic distribution mapping suggests a possible continuation of the New Bedford gneissic terrane that outcrops 25 km to the west. Dolomitic rocks may represent a lithified fault gauge material at the eastern edge of the gneissic zone. Basalts/diabases are interpreted to be post-metamorphic dikes associated with Mesozoic rifting.

Access & Use Information

Public: This dataset is intended for public access and use. License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

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Metadata Created Date June 1, 2023
Metadata Updated Date October 26, 2023

Metadata Source

Harvested from DOI EDI

Additional Metadata

Resource Type Dataset
Metadata Created Date June 1, 2023
Metadata Updated Date October 26, 2023
Publisher U.S. Geological Survey
Identifier USGS:709dc7ba-d758-4814-9825-7557704e1879
Data Last Modified 20211116
Category geospatial
Public Access Level public
Bureau Code 010:12
Metadata Context
Metadata Catalog ID
Schema Version
Catalog Describedby
Harvest Object Id ff3744bd-209e-4c4f-87b5-77b46ba29cd3
Harvest Source Id 52bfcc16-6e15-478f-809a-b1bc76f1aeda
Harvest Source Title DOI EDI
Metadata Type geospatial
Old Spatial -70.615932,41.61107,-70.50196,41.66787
Publisher Hierarchy White House > U.S. Department of the Interior > U.S. Geological Survey
Source Datajson Identifier True
Source Hash 38001b5286827fa0e62eee7dc575e72116f8dc12de6dca35eed89306a61efa06
Source Schema Version 1.1
Spatial {"type": "Polygon", "coordinates": -70.615932, 41.61107, -70.615932, 41.66787, -70.50196, 41.66787, -70.50196, 41.61107, -70.615932, 41.61107}

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