2006 Appalachian Tectonic Studies Group Field Trip
Pennsylvania Piedmont east of the Susquehanna River
Don Wise, University of Massachusetts, firstname.lastname@example.org
Bob Ganis, email@example.com
This years trip focused on the Pennsylvania Piedmont east of the Susquehanna River. It involves mostly Taconian structures and events but includes a healthy overprint of younger, largely Alleghanian structures.
Click on a link below to view a picture or watch the movie
The trip is a two-day version of the shorter one just completed for the NE GSA meetings. That one-day trip included about 60% of the same stops (Previewed and argued over mightily by the likes of Jim Hibbard, Cees van Staal and Bob Wintsch). The litho-tectonic map of the area below is from the 2006 NE GSA guidebook (available from Noel Potter firstname.lastname@example.org).
Saturday we saw outcrops with some fancy structures and minor dolomitization superimposed on the transition from carbonate platform to olistostrom and slope carbonates. We continued on into the complex thrust and multiple fold structures along the oft-debated Martic line, and then saw evidence bearing on Faill and Smiths story of offshore, deep-water deposits of the infamous Peach Bottom slate belt and Peters Creek formation. The day ended at Chickies Rock where paleo-vertical Skolithos worm tubes show cleavage formation by Taconian layer-parallel shortening followed by Alleghanian cleavage-piracy that created plunging folds without sympathetic plunge rotation of the internal fabric. (Awwwkk !!). Dinner was at a great brew pub.
Early on Sunday we visited overturned Taconian (mostly) nappe structures of the carbonate platform in the famous Rheems Quarry. Two other quarries showed many types of boudinage formation, an Ordovician ash bed in an overturned nappe limb, plus carbonate mylonite development along a regional scale Allegnainian thrust fault. During the trip we discussed Taconian foreplay in the foreland with Ganiss graptolite-based evidence for the offshore development of several types of allochthons, their subsequent climb onto the platform, and their progressive emplacement into the foreland basin as the Dauphin Formation, a precursor now separated from the traditional Martinsburg Formation. The evidence argues that the famous Hamburg klippe as generally known and defined is fiction. ended in the Great Valley a few miles east of Harrisburg on Route 39.
Don Wise, University of Massachusetts
Rev. 2008 May 15