This story highlights a current research project at the Hubbard Brook Experimental Forest. To read more about research projects at HBEF, visit Current Research page. Check back regularly to learn about new research projects.
The bedrock geology of the Hubbard Brook Experimental Forest: Results of new 1:10,000 mapping

 

  Contact Info:
 

Gregory J. Walsh
US Geological Survey
PO Box 628, 87 State Street, Rm 324
Montpelier, Vermont 05601 USA
phone: (802) 828-4528
(802) 828-4465 fax
gwalsh@usgs.gov

Bill Burton
U.S. Geological Survey
National center MS 926A
Reston, VA 20192
phone: (703) 648-6904
(703) 648-6953 fax
bburton@usgs.gov

Abstract
THE BEDROCK GEOLOGY of the Hubbard Brook Experimental Forest consists of metasedimentary rocks of the Silurian Rangeley and Perry Mountain Formations that have been intruded by Devonian granitoids and Cretaceous-Jurassic mafic dikes. The metasedimentary rocks were affected by at least two episodes of deformation in the Devonian Acadian orogeny and metamorphic conditions that produced sillimanite-muscovite mineral assemblages. The eastern portion of the watershed is underlain by schists of the Rangeley Formation, overlain in the southern part of the watershed by quartzite and schist of the Perry Mountain Formation. The western part of the watershed contains a large body of Devonian Kinsman Granodiorite which intruded Rangeley Formation schists semi-concordantly. Volumetrically minor dikes of Devonian granite and tonalite cut lithologic contacts and appear to be syn- or post-Kinsman. The map pattern is dominated by northeast- to northwest-trending, moderately to steeply-north dipping F2 and F3 folds, while map-scale F1 folds are defined by the Perry Mountain-Rangeley contact. Steeply dipping fractures in the area show a preferred northeast orientation, in agreement with subsurface fracture orientations in the CO well field. Cretaceous-Jurassic mafic dikes and normal faults also show preferred northeast orientations suggesting that the stress field that produced the dominant brittle fabrics in the area was probably extensional in a northwest to southeast direction.

For further information see: http://geology.er.usgs.gov/eespteam/brass/hbef.html