ABSTRACT The Fernow Experimental Forest (the “Fernow”) is an 1860-ha (4600-acre) research forested watershed in Parsons, West Virginia, USA. The Fernow has been in operation since 1934 and has historically been the site of timbering and silvicultural research programs. Beginning in the 1950s, a water quality research program was established in the Fernow to assess the effects of different forestry management techniques on water quantity and quality. As a result, most peer-reviewed research from the Fernow has focused on water quality data directly related to forestry efforts with little mention of the effects of geology, hydrogeology, or climate on water resources in the Fernow. Further, the Fernow is representative of Appalachian headwater mountain watersheds and is a protected and secure research site in the greater Monongahela National Forest. This, in combination with the long-term data records from the water research program, make the Fernow an ideal location for further geologic and hydrologic investigations in forested mountain watersheds. The geology of the Fernow is dominated by moderately dipping Paleozoic-aged strata with local karst features (e.g., springs) occurring in one unit. The hydrology of the Fernow consists of intermittent and perennial streams that are reactive to seasonal weather patterns. This field guide serves as an overview of the geology and hydrology of the Fernow and surrounding region to be used as a teaching and recruitment tool to advance the geologic understanding of Allegheny Mountain headwaters.

ABSTRACT During the Pleistocene, the Laurentian Ice Sheet extended southward into northwestern Pennsylvania. This field trip identifies a number of periglacial features from the Appalachian Plateaus and Ridge and Valley provinces that formed near the Pleistocene ice sheet front. Evidence of Pleistocene periglacial climate in this area includes glacial lake deposits in the Monongahela River valley near Morgantown, West Virginia, and Sphagnum peatlands, rock cities, and patterned ground in plateau areas surrounding the Upper Youghiogheny River basin in Garrett County, Maryland, and the Laurel Highlands of Somerset County, Pennsylvania, USA. In the high-lying basins of the Allegheny Mountains, Pleistocene peatlands still harbor species characteristic of more northerly latitudes due to local frost pocket conditions. Pleistocene fauna preserved in a cave deposit in Allegany County, Maryland, record a diverse mammalian assemblage indicative of taiga forest habitat in the Ridge and Valley province.

ABSTRACT With waterfalls and the deepest gorge in Pennsylvania, Ohiopyle State Park provides opportunities to observe a variety of habitats and three-dimensional (3-D) exposures of the Pennsylvanian sandstone most responsible for shaping Laurel Highlands landscapes. Evidence for the relationship between bedrock, ancient climates, and the landscape can be observed at some of the most scenic natural features of the park: Baughman Rock Overlook, Cucumber Falls, Ohiopyle Falls, Meadow Run Waterslide and Cascades, and Youghiogheny River Entrance Rapid. Channel azimuths and lateral variations in thickness of upper Pottsville fluvial/deltaic sandstone suggest that deposition was influenced by deformation of this part of the Allegheny Plateau during the Alleghanian orogeny. Geologic features of Pottsville sandstone outcrops include a 10-m- (~33-ft-) long Lepidodendron fossil and a 3-D exposure of a meter-high Pennsylvanian subaqueous sand dune and scour pit. Cosmogenic age dating has indicated very slow erosion of hard sandstone in an upland location at Turtlehead Rock and informed estimation of Pleistocene/Holocene waterfall retreat rates of Ohiopyle and Cucumber Falls. Bedrock exposures supporting scour habitats along the Youghiogheny River occur only in a limited area of Youghiogheny Gorge where knickpoint migration and bedrock erosion were relatively recent. Geologic factors, including locations of major tributaries, development of bars that constrict river flow, and proximity of Homewood sandstone outcrops as sources of boulder obstacles in the river, contributed to the class, location, and nature of whitewater rapids in the lower Youghiogheny River.

Subsurface sandstone samples of the Upper Jurassic (Oxfordian) Norphlet Formation erg deposits and (Kimmeridgian) Haynesville Formation sabkha deposits were collected from wells in the eastern Gulf of Mexico for U-Pb detrital zircon provenance analysis. Norphlet Formation samples in southwestern Alabama are characterized by detrital zircon ages forming two dominant populations: (1) 265–480 Ma, associated with Paleozoic Taconic, Acadian, and Alleghanian orogenic events of eastern Laurentia, and (2) 950–1250 Ma, associated with the Grenville orogenies of eastern Laurentia. These detrital zircon ages indicate derivation from Laurentian and Laurentian-affinity sources, including erosion of Paleozoic strata of the remnant Alleghanian fold-and-thrust belt and Black Warrior foreland basin, as well as Laurentian cratonic rocks exposed in remnant Appalachian orogenic highlands and eastern Gulf of Mexico rift-related horst blocks. In contrast, Norphlet Formation samples from the offshore Destin Dome exhibit a major population of 540–650 Ma zircon grains, along with a small population of 1900–2200 Ma zircon grains; these ages are interpreted to indicate contribution of sediment to the Norphlet erg from peri-Gondwanan terranes sutured to eastern Laurentian, as well as from the Gondwanan Suwannee terrane, which remained attached to North America after the rifting of Pangea. Samples from south-central Alabama yield subequal proportions of four major age populations: 250–500 Ma, 520–650 Ma, 900–1400 Ma, and 1950–2250 Ma. These ages indicate sediment was sourced by both Laurentian/Laurentian-affinity and Gondwanan/Gondwanan-affinity rocks, either through a combination of these rocks in the source area, or intrabasinal mixing of Laurentian/Laurentian-affinity sediment with Gondwanan/Gondwanan-affinity sediment. Detrital zircon provenance data from the overlying Haynesville Formation clastics of the Destin Dome offshore federal lease block also show the signature of Gondwanan/Gondwanan-affinity sediment input into the eastern Gulf of Mexico, suggesting that paleotopography affecting Norphlet Formation deposition persisted throughout much of the Late Jurassic. However, samples from the Pennsylvanian Pottsville Formation synorogenic fill of the Black Warrior Basin and Middle Cretaceous Rodessa Formation marginal marine sandstone lack evidence for any significant contribution of Gondwanan or Gondwanan-affinity detritus to the basin, indicating that transport of Gondwanan/Gondwanan-affinity zircon to the eastern Gulf of Mexico was due to early Mesozoic uplift, erosion, and/or paleodrainage pattern development. These results, along with previously reported detrital zircon provenance of Triassic and Jurassic sandstone of the southern United States, suggest that early Mesozoic sediment supply in southern North America was closely associated with erosion of Gondwanan/peri-Gondwanan crust docked along the Suwannee-Wiggins suture, which likely extended westward from the Suwannee terrane to the Yucatan-Campeche terrane; much of this Gondwanan/peri-Gondwanan crust remained docked along the Suwannee-Wiggins suture after the rifting of Pangea and prior to opening of the Gulf of Mexico.

Data from thousands of coalbed methane wells, conventional oil and gas wells, and five regional seismic-reflection profiles show evidence of relationships among multiple extensional events and Appalachian thrusting in the area of the Alabama Promontory and Black Warrior Basin. The oldest extensional event is of late Precambrian to early Middle Cambrian age, associated with Iapetan rifting. Along the southeastern margin of the promontory, in the northeastern part of the Birmingham graben system, a fill sequence older than the Rome Formation (Early Cambrian) is inferred. Normal faults along both sides of the promontory were active from Early Cambrian to early Middle Cambrian, as indicated by expanded hangingwall sections of the Rome and Conasauga Formations. In the Black Warrior Basin, some basement-involved normal faults were active during deposition of the Ketona and Knox carbonates (Late Cambrian–Early Ordovician). Middle Cambrian to Early Ordovician extension coincided with the inception and opening of the Rheic Ocean. Small amounts of growth occurred on some normal faults and on folds at the leading edge of the Appalachians during deposition of the Pottsville Formation (early Pennsylvanian, Morrowan). Major thin-skinned and basement-involved normal faulting occurred in the Black Warrior Basin after deposition of the preserved Pottsville section, probably during Atokan time. The extensional thin-skinned detachments are in or at the base of the Pottsville Formation and the top of the Conasauga Formation. Major Appalachian thrusting occurred after the main episode of normal faulting, perhaps during the late Pennsylvanian.

Continental crust is recycled into orogenic forelands by the distinct but inter- related processes of tectonic imbrication and sedimentary dispersal. Tectonic loading by the orogen drives flexural subsidence of a foreland basin, and the orogen provides a source of sedimentary detritus to fill the basin. Detrital zircons in Pennsylvanian-age sandstones in the Appalachian (Alleghanian) foreland basin reflect an Alleghanian orogenic source of recycled and primary detritus from Grenville-age basement rocks and Iapetan synrift rocks, which also yield pre-Grenville recycled craton-derived detrital zircons. Minor contributions are from Taconic- and Acadian-age plutons and accreted Gondwanan terranes. Ages of the detrital zircons show that most of the synorogenic clastic-wedge sediment was recycled from older continental crustal rocks. Cratonward thrusting of crystalline thrust sheets over the foreland recycles continental crustal rocks from the continental margin and thickens the continental crust. Along the Alleghanian foreland, the Blue Ridge thrust sheet of crystalline basement rocks and Piedmont thrust sheets of metasedimentary rocks represent imbrication and thickening of rocks of continental crustal composition. Both tectonic imbrication in foreland thrust sheets and sediment dispersal into the foreland basin recycle and thicken continental crust.

Multiple levels of frontal ramps and detachment flats accommodate tectonic shortening in contrasting deformation styles at different levels in a mechanically hetero geneous stratigraphic succession in a foreland thrust belt. The late Paleozoic Appalachian thrust belt in Alabama exhibits a balance of shortening in contrasting deformation styles at different stratigraphic levels. The regional décollement is in a weak unit (Cambrian shale) near the base of the Paleozoic succession above Precambrian crystalline basement rocks. Basement faults, now beneath the décollement, controlled the sedimentary thickness of the Cambrian shale and the location of high-amplitude frontal ramps of the regional stiff layer (Cambrian-Ordovician massive carbonate); shortening in a mushwad (ductile duplex) from thick Cambrian shale is balanced by translation of the regional stiff layer at a high-amplitude frontal ramp above a basement fault. A trailing, high-amplitude, brittle duplex of the regional stiff layer has a floor on the regional décollement and a roof that is also the floor of an upper-level, lower-amplitude, brittle duplex. The roof of the upper-level brittle duplex is a diffuse ductile detachment below an upper-level mushwad, with which parts of the brittle duplex are imbricated. The basal detachment of the upper-level mushwad changes along strike into a frontal ramp at a location coincident with a sedimentary facies change in the weak shale unit that hosts the mushwad. The roof of the upper-level mushwad is a brittle massive sandstone. Shortening on the regional décollement is balanced successively upward through contrasting tectonic styles in successive mechanically contrasting stratigraphic units.

Abstract The thickest and most laterally continuous upper Carboniferous molasse in the central Appalachians is located in the Southern Anthracite Field of northeastern Pennsylvania. Substantial deposits extend throughout northeastern Pennsylvania where >90% of the total anthracite (original reserves) in the United States and the thickest coal beds of the eastern United States are located. The abundance of and demand for this resource allowed the region to prosper in the nineteenth and twentieth centuries. In Pottsville, Pennsylvania, the exposed Upper Mississippian to Middle Pennsylvanian molasse reveals a progressive evolution from a semiarid alluvial plain to a semihumid alluvial plain to a humid alluvial plain. The anthracite beds occur and thicken with increased humid conditions. The progression is also exposed in Tamaqua, Pennsylvania, where convenient access to the underlying Lower Mississippian strata is available, thus providing a section of all Carboniferous formations in the region. Finally, in Lansford, Pennsylvania, a renovated deep anthracite mine illustrates the historical methods and working conditions that existed to extract the valuable resource and allow the region to flourish and fuel the Industrial Revolution.