Overview and Highlights

Through photos, field notes, and interpretations, this blog attempts to describe and contextualize the geologic formations of Western New England, as seen in outcrop on a series of five field trips.  Highlights are as follows:

• Precambrian rocks of the Grenville basement are the oldest units visited, and were seen primarily in field trip 5 and the first stop of field trip 1.
• During the Precambrian to Early Cambrian breakup of Rodinia and concurrent opening of the Iapetus Ocean, a series of rift sediments was deposited. These sediments are the protoliths for the various orogenically metamorphosed formations in field trips 1 and 2.  The specific lithologies of these rocks are indicative of the sea level in the locations at which they were deposited.
• The Hoosac Schist of field trip 2 as well as all the formations seen in field trip 3 are derived from passive margin slope-rise deposits, from deeper water than the synrift deposits.  The passive margin persisted from the Early Cambrian through the Middle Ordovician.
• The passive Laurentian margin ended with its Ordovician collision with the Shelburne Falls arc.  Outrcrops reflective of active tectonic processes such as subduction and volcanism were seen in field trip 4.  

  

  Figure 0.1: Tectonic Units of western Vermont and Massachusetts.  This figure will occur throughout the
  blog, with the relevant sequence highlighted.

References (entire blog):

Allen, J.S., W. A. Thomas, and D. Lavoie, 2010. The Laurentian margin of northeastern North America.  Geologic Society of America Memoirs, 206, 71-90.

Cawood, P. A., P. J. McCausland, and G. R. Dunning, 2001.  Opening Iapetus: constraints from the Laurentian margin in Newfoundland.  Geological Society of America Bulletin, 113, 443-453.

Courtillot, V., and G. E. Vink, 1983. How continents break up. Scientific American, v.? 43-49.

Karabinos, P., 2013.  Class and lab lecture/discussion. GEOS 401, Williams College, Fall 2013.

Karabinos, P., S. D. Sampson, J. C. Hepburn, and H. Stoll, 1998. Taconian orogeny in the New England Appalachians: collision between Laurentia and the Shelburne Falls arc. Geology, 26, 215-218.

Lister, G. S., M. A. Etheridge, and P. A. Symonds, 1986. Detachment faulting and the evolution of passive continental margins.  Geology, 14, 246-250.

Weaver, P. P. E., R. B. Wynn, N. H. Kenyon, and J. Evans, 2000. Continental margin sedimentation, with special reference to the north-east Atlantic margin. Sedimentology, 47, 239-256. 

Williams, H., and R. N. Hiscott, 1987. Definition of the Iapetus rift-drit transition in Western New Foundland. Geology, 15, 1044-1047.

Withjack, M. O., R. W. Schlishe, and P. E. Olsen, 1998. Diachronous rifting, driting, and inversion on the pasive margin of central eastern North America: an analog for other passive margins, AAPG Bulletin, 82, 817-835.