ABSTRACT This one-day field trip will visit northern Erie County in northwestern Pennsylvania, USA, and is divided into two parts. The first part will highlight brittle and ductile deformation preserved in Upper Devonian bedrock. It is possible that this deformation occurred in relation to the Alleghenian orogeny during the late Paleozoic. However, some of this deformation displays possible evidence of postdating Wisconsin glaciation, but this interpretation is speculative and based largely on possible topographic disruption of Quaternary river terrace deposits. Morphologic characteristics of outcrops in creeks that expose these tectonic structures will be used as a starting point to discuss structure origin, timing, and their implications. The second part of the trip will visit Erie Bluffs State Park (EBSP) and will examine ongoing mass wasting of bluffs along the southern Lake Erie shoreline. The timing (as determined from dendrochronological analyses) and styles of mass wasting that have occurred at EBSP will be discussed and compared to two other locations along Pennsylvania’s Lake Erie shoreline. An appended road log serves as a geologic guide to the features and processes highlighted on this trip.

Abstract Berea sandstone, a potential Global Heritage Stone Resource, has been one of the most widely used sandstones in North America. This Paleozoic sandstone, quarried for more than 200 years in Ohio, has been used across much of the continent. Thousands of commercial, residential, ecclesiastical, government and other structures have been built with Berea sandstone, including Thomas Worthington's mansion in Chillicothe, Ohio, the Michigan Capitol in Lansing, Michigan, the Carnegie Library and Natural History Museum Building in Pittsburgh, Pennsylvania, and parts of the Parliament buildings in Canada. Grindstones made from Berea sandstone were shipped throughout North America, as well as to the Caribbean, South America, Europe and Asia. The stone is celebrated in a number of locations, notably Berea and Amherst, where quarries have been important historical sources of this stone. It has been known by a number of different geological and commercial names, including Berea grit and Amherst stone, complicating its identification from historical sources. Stone from the most productive quarries, however, was known to be homogeneous and can be identified by its quartz–arenite to sublithic–arenite composition, its fine to medium sand (125–350 µm) grain size and iron-cement spots. Berea sandstone continues to be quarried today in Erie and Lorain counties.

ABSTRACT Silurian-age (Niagaran) reefs in the Michigan Basin have long been interpreted as relatively homogeneous units, despite production histories that strongly suggest the reefs are heterogeneous in both lateral and vertical dimensions. In an attempt to better illustrate reservoir heterogeneity in these reefs, a three-dimensional (3-D) sequence stratigraphic model was produced for the Ray Reef field. The resulting 3-D Petrel model incorporates 28 wells in the field using a combination of gamma-ray and neutron logs, porosity and permeability data from whole-core analysis, and facies descriptions from eight cores evenly distributed within the reef complex. Comparison of porosity and permeability values within the diverse depositional facies clearly shows trends related to the individual facies and positioning within the sequence hierarchy. Incorporation of the sequence stratigraphic framework into the 3-D model illustrates the episodic nature of reef growth as exhibited by the stacked nature of reef and capping grainstones, often separated by well-developed exposure horizons. The model also suggests a distinct difference between windward and leeward margins in both the geometry of the reef complex and the distribution of reservoir-prone facies. Windward margins are steeper due to higher rates of aggradational growth, and they typically contain higher percentages of reservoir-quality rock in both the reef core and forereef facies. Utilization of the sequence stratigraphic approach illustrates that the vertical reservoir heterogeneity often predicted from production in these reefs may be controlled in large part by the combination of vertical stacking patterns of facies within third- and fourth-order sequences.

Abstract Western Pennsylvania is rich in oil history, and many of the fledgling petroleum industry’s “firsts” happened right here between the late nineteenth and early twentieth centuries. First and foremost, it is home to the Drake Well, the first-ever economic well intentionally drilled to produce oil. In addition, western Pennsylvania has bragging rights to various industry advancements, from the way geologic samples were collected and interpreted, to how wells were drilled and stimulated for production, to early oil refining techniques, marketing, and production. In this field guide, we discuss the petroleum geology and history of western Pennsylvania in general and three important oil-producing sites in particular: (1) the McClintock #1 Well, Rouseville; (2) the Drake Well, Titusville; and (3) Muddy Creek oil field, Prospect. Each of these sites produced oil from Upper Devonian reservoirs and spurred additional petroleum exploration and development in the central Appalachian basin. This field trip generally follows the GSA guide published from the 2011 Joint Meeting of the GSA Northeastern and North-Central Sections in Pittsburgh (available at http://fieldguides.gsapubs.org/ ): Carter, K.M., and Flaherty, K.J., 2011, The old, the crude, and the muddy: Oil history in western Pennsylvania, in Ruffolo, R.M., and Ciampaglio, C.N., eds., From the Shield to the Sea: Geological Field Trips from the 2011 Joint Meeting of the GSA Northeastern and North-Central Sections: Geological Society of America Field Guide 20, p. 169–185, doi:10.1130/2011.0020(08).

ABSTRACT This annual meeting of the North-Central Section of the Geological Society of America provides an opportunity to visit a working underground salt mine on a field trip. The trip leaders will take a group into the Detroit Salt Mine, which is located approximately 1200 ft (364 m) deep beneath a portion of the city of Detroit, Michigan. This mine extracts salt through a room and pillar mining process from the Silurian Salina "F" Salt formation. Currently the mined salt is used primarily as crushed salt for ice control throughout the upper Midwest. The company is mining a 30-ft-thick seam of bedded halite. Thin beds of anhydrite and/or dolomite are occasionally interbedded with the high-purity halite.

Abstract Northwestern Pennsylvania was glaciated by the Grand River sublobe of the Erie Lobe. Glacial advances occurred at least three times during the pre-Illinoian (Slippery Rock, Mapledale, and Keefus), once during the Illinoian (Titusville), and four Late Wisconsinan (Kent, Lavery, Hiram, and Ashtabula) tills have been identified. While the area was studied for over 50 years by George White and associates, there are numerous details that remain unknown. The Titusville Till, which comprises the bulk of the glacial sediment, contains up to five separate sheets separated by sand and gravel. The origin of the numerous sheets is still not clear. The Kent glaciation resulted in extensive deposition in proglacial lakes and caused numerous local drainage diversions. Interpretations of the surficial geology around Conneaut Lake have changed a couple of times. Originally interpreted to be formed by a lobe of Hiram ice, it was later determined to be part of a widespread area of Lavery ice. Recent work supports the original Hiram interpretation. Since glaciation, streams in northwestern Pennsylvania have incised into the glacial sediments and have developed fine-grained floodplains within glacially scoured valleys. Lake sediments and alluvial stratigraphy suggests that general climate amelioration during the Holocene epoch was interrupted by episodes of landscape instability. Deforestation by European settlers is the most recent event appearing in the stratigraphic record and resulted in deposition of as much as 2 m of post-settlement alluvium.