We present a newly compiled geologic map of the Pine Mountain window based on available 1:24,000 (and smaller) scale geologic maps; this map provides an improved basis to reconcile long-standing issues regarding tectonic evolution. We integrate sensitive high-resolution ion microprobe (SHRIMP) single-grain U-Pb ages of igneous, metamorphic, and detrital zircons from Grenville basement rocks, associated metasedimentary units, and cover rocks to help clarify the pre-Appalachian history and to better delimit the distribution of Laurentian versus peri-Gondwanan and Gondwanan units along the southeast flank of the window. U-Pb results indicate that some units, which earlier had been correlated with Neoproterozoic to Early Cambrian Laurentian rift deposits of the Ocoee Supergroup (i.e., Sparks-Halawaka Schist), actually are supracrustal rocks deposited prior to ~1100 Ma that were intruded and metamorphosed during the Ottawan phase of the Grenville orogeny. Zircons from the Phelps Creek Gneiss are 425 ± 7 Ma and overlap in time with plutons that intruded rocks of the Carolina superterrane during the Silurian (i.e., the Concord-Salisbury suite). The host units to the Phelps Creek Gneiss had also previously been interpreted as Sparks-Halawaka Schist, but field relations combine with the Silurian intrusive age to suggest that they rather belong to the peri-Gondwanan Carolina superterrane, helping to refine the position of the Central Piedmont suture in its most southern exposures. Results suggest that the Pine Mountain window is not framed by a single fault, but by Alleghanian faults of different timing, rheology, and kinematics, some of which were reactivated while others were not. The new map and U-Pb dates reveal that the southwesternmost exposures of the Central Piedmont suture are located farther northwest, so the width of the Pine Mountain window narrows from 22 km wide in central Georgia to only 5 km in Alabama. At its narrowest, the flanks of the Pine Mountain window are marked by two relatively thin normal faults (the Towaliga and Shiloh faults, northwest and southeast, respectively) that have excised the wider, earlier-formed mylonite zones. All of the Alleghanian faults are cut by later high-angle, normal and left- and right-slip brittle faults (Mesozoic?), which also influenced the present configuration of the window.

Abstract Contributors: Hans AbramsonWard, Geomatrix Consultants, Inc., 2101 Webster St., Suite 1200, Oakland, California 94612, USA; Julie Bawcom, California Geological Survey, 17501 North Highway 101, Willits, California 95490, USA; John Boatwright, U.S. Geological Survey, 345 Middlefield Rd., M.S. 977, Menlo Park, California 94025, USA; Todd Crampton, Geomatrix Consultants, Inc., 2101 Webster St., Suite 1200, Oakland, California 94612, USA; Wayne Goldberg, City Manager's Office, 100 Santa Rosa Ave., Rm. 10, Santa Rosa, California 95404, USA; Kathryn L.Hanson, Geomatrix Consultants, Inc., 2101 Webster St., Suite 1200, Oakland, California 94612, USA; Victoria E.Langenheim, U.S. Geological Survey, 345 Middlefield Rd., M.S. 989, Menlo Park, California 94025, USA; MortLarsen, Department of Geology, Humboldt State University, 1 Harpst St., Arcata, Cali-fornia 95521, USA; Gaye LeBaron, Press Democrat, P.O. Box 569, Santa Rosa, California 95402, USA; Darcy K.McPhee, U.S. Geological Survey, 345 Middlefield Rd., M.S. 989, Menlo Park, California 94025, USA; William V. McCormick, Kleinfelder, 2240 Northpoint Parkway, Santa Rosa, California 95407, USA; Robert J. McLaughlin, U.S. Geological Survey, 345 Middlefield Rd., M.S. 973, Menlo Park, California 94025, USA; Craig A.McCabe, U.S. Geological Survey, 345 Middlefield Rd., M.S. 973, Menlo Park, California 94025, USA; David P.Schwartz, U.S. Geological Survey, 345 Middlefield Rd., M.S. 977, Menlo Park, California 94025, USA; GarySimpson, SHN Consulting Engineers and Geologists, 812 W. Wabash Ave., Eureka, California 95501, USA; Frank H. (Bert)Swan, Consulting Geologist, 240 Laidley Street, San Francisco, California 94131, USA This guidebook is for a two-day trip: the first part (Day 1) takes place in and near the city of Santa Rosa and on the Rodgers Creek fault in Sonoma County; the second part (Day 2) will go to stops in the town of Willits, on the northern Maacama fault, in Mendocino County. The Rodgers Creek and Maacama faults are major strands of the San Andreas fault system in northern California. The two faults are separated by a right step and may be considered the northern extension of the Hayward and Calaveras faults, which branch from the San Andreas fault south of the San Francisco Bay area (Fig. 1 A). This system of faults accommodates almost a quarter of the total right-slip motion between the Pacific and North American tectonic plates. Slip is released in large, episodic earthquakes and, on some faults, such as the northern Maacama fault, by slow, steady creep.

ABSTRACT Exploration for oil in the Norphlet reservoir in the deep-water Gulf of Mexico began in 2003 at prospect Shiloh (DC269). The well found oil but not an economic volume. The second prospect, Vicksburg (DC353), was drilled in 2007. This well found a larger in-place volume of oil, but with an immovable solid hydrocarbon component within pore spaces, there was great uncertainty as to the potential producible volumes. Two subsequent wells (Fredericksburg [DC486] and Antietam [DC268]) were dry and had a very small amount of oil, respectively. Finally, in late 2009, the fifth well (Appomattox [MC392]) was a significant discovery of high-quality oil in a thick aeolian Norphlet sandstone.