Regional Tectonics Geology 200 Geology for Environmental Scientists Fig.23.10. Differential erosion in horizontal strata Fig. 23.19. Basin & Range model landscape Extension experiment in tectonic modeling lab exercise 2009 Fig. 23.21. Landscape development in basalt plains Tectonics of the Central Appalachians • Appalachian Plateau – Low and High • Valley and Ridge • Great Valley • Blue Ridge High Plateau Great Low Valley Valley Plateau and Ridge Blue Rid ge Relief Map Fig. 23.15. Differential erosion in folded rocks Relief Map with county boundaries Satellite Image Variation in fold wave length vs. fold amplitude. Open folds are typical of the Appalachian Plateau , whereas tight folds are typical of the Valley and Ridge. Isoclinal folds are not common in the Appalachians. View of open folds on the Appalachian Plateau, Garrett Co., Maryland. West-dipping Hogbacks Geologic Cross Section from Seneca Rocks to Elkins, WV Thrustinggpp of the Wills Mtn Duplex created open folds to the west. Plateau Seneca Rocks Valley & Ridge Geologic Map of the central Appalachians (Dunne, 1996) Various interpretations of Valley and Ridge geology (Dunne, 1996) WMA= Wills Mtn. Anticline, BTS= Broad Top Synclinorium, CMA= Cacapon Mtn. An tic line, NMT = N or th Mt n. Thrust Cross section by Kulander and Dean (1986) Tuscarora Ss. ifin roof sequence Cambro-Ordovician carbonates Compression experiment in tectonic modlideling l lbab exerci se 2009 2009 Preferred cross section of Dunne (1996) Roof sequence Thrust sheets Deformed quartz vein approximately 100 m long. AlllA small scale exampl lfflddhble of a fold and thrust belt. Folded soil layer along a lake in Wisconsin caused by thrusting of ice on shore byyg high winds durin gpgg spring thaw. Note the formation of the thrust propagation fold and the anticline core exposed in the background by a tear fault. Wills Mountain anticline at Greenland Gap 2007 2008 Aerial view of Dolly Sods and Wills Mountain Anticline North Fork Gap Geology of North Fork Gap through Wills M ountai n A nti cli ne Jack Renton View of the Valley and Ridge from Dolly Sods overlook North Fork Gap View of the Valley and Ridge from Dolly Sods overlook Hopeville Anticline Aerial view of Seneca Rocks and Germany Valley Geology of Seneca Rocks and Germany Va lley, Will s M ountai n A nti cli ne Jack Renton Aerial view of Germany Valley, a breached anticline. Note Seneca Rocks. Seneca Rocks -- vertical beds of the Tuscarora Sandstone 2003 Geology 200 class on top of Seneca Rocks 2004 Geology 200 class on top of Seneca Rocks 2005 Geology 200 class on top of Seneca Rocks 2006 Geology 200 class (partial) on top of Seneca Rocks 2007 Geology 200 class (partial) on top of Seneca Rocks 2008 Geology 200 class 2006 Geolo(partial)gy on 200 top class of (partial)Seneca on top Rocksof Seneca Rocks 2009 Geology 200 class on top of Seneca Rocks Tuscarora Sandstone at Greenland Gap. Examppple of a competent rock unit. 2004 2008 Tightly folded Silurian rocks at Pinto, Maryland. Example of incompetent rocks in roof sequence . Sideling Hill Syncline on I-68, Maryland; looking west. An example of an open fold. The synclines often form in the “sags” between thrust sheets. Anticlinorium formed by thrust sheet. Sy ncline formed by sag bet ween thr ust sheets. syncline Satellite image of central Appalachians Valley and Ridge Shenandoah or Great Valley Blue Ridge Mtns Potomac River False color satellite image of folded sedimentary rocks,,pp central Appalachian Mountains. Orogenic belt with complex folding The eastern margin of Laurentia (North America) at the beginning of the Paleozoic. Morgantown Geography of Laurentia at the beginning of the Paleozoic. The eastern edge of Laurentia (North America) during the Ordovician before the start of the Paleozoic orogenies that formed the Appalachian Mtns. Deformation during the Late Ordovician Taconic Orogeny in eastern Pennsylvania. Deformation during the Permian-age Allegheny Orogeny in Pennsylvania. Morgantown Fig. 23.5. Rates of erosions of a mountain belt Other Mountain Belts Fig. 23.1 Fig. 23. 18d. Faceted spurs in block faulted mountains Wasatch Mountains, UT Canadian Rockies Folded bedding with axial planar cleavage - Taconic Mtns . of Vermont Folds in Mesozoic sedimentary rocks of the Himalayas: Seafloor rocks of the Tethys Seaway . Fault propagation fold, Mesozoic of Pakistan.