Published by the American Geophysical Union as part of the Field Trip Guidebooks Series, Volume 203. Rocks that once constituted parts of the southeastern margin of Proterozoic North America are widely exposed in internal and external massifs throughout the Appalachian orogen (Rodgers, 1987; Reed, 1987). The oldest rocks exposed in these massifs are plutonic rocks and gneisses emplaced or metamorphosed during the 1000 to 1100 Ma Grenville orogeny. These Middle Proterozoic basement rocks are unconformably overlain by metasedimentary and metavolcanic sequences of Late Proterozoic age that record rifting events during the early stages of opening of Iapetus, the early Paleozoic ancestor of the present Atlantic Ocean. Both basement and cover rocks are exposed in the Blue Ridge anticlinorium, a major tectonic element that extends for more than 300 km northeastward from near Lynchburg, Virginia to the vicinity of Carlisle, Pennsylvania (Figure 1). Proterozoic rocks in the core of the anticlinorium are stratigraphically overlain by lower Paleozoic rocks. On the northwest limb of the anticlinorium these strata include a basal Cambrian clastic sequence (the Chilhowee Group), a Cambrian through Middle Ordovician miogeoclinal sequence consisting of carbonates and mature clastics, and various shallow marine to terrestrial strata of Late Ordovician to Carboniferous age. Collectively they constitute the classic sequence of the Valley and Ridge province of the central Appalachians.

Published by the American Geophysical Union as part of the Field Trip Guidebooks Series, Volume 203. Rocks that once constituted parts of the southeastern margin of Proterozoic North America are widely exposed in internal and external massifs throughout the Appalachian orogen (Rodgers, 1987; Reed, 1987). The oldest rocks exposed in these massifs are plutonic rocks and gneisses emplaced or metamorphosed during the 1000 to 1100 Ma Grenville orogeny. These Middle Proterozoic basement rocks are unconformably overlain by metasedimentary and metavolcanic sequences of Late Proterozoic age that record rifting events during the early stages of opening of Iapetus, the early Paleozoic ancestor of the present Atlantic Ocean. Both basement and cover rocks are exposed in the Blue Ridge anticlinorium, a major tectonic element that extends for more than 300 km northeastward from near Lynchburg, Virginia to the vicinity of Carlisle, Pennsylvania (Figure 1). Proterozoic rocks in the core of the anticlinorium are stratigraphically overlain by lower Paleozoic rocks. On the northwest limb of the anticlinorium these strata include a basal Cambrian clastic sequence (the Chilhowee Group), a Cambrian through Middle Ordovician miogeoclinal sequence consisting of carbonates and mature clastics, and various shallow marine to terrestrial strata of Late Ordovician to Carboniferous age. Collectively they constitute the classic sequence of the Valley and Ridge province of the central Appalachians.

As a final product of the International Geological Correlation Program (IGCP) Project 217, this volume brings together significant advances in the understanding of Proterozoic crustal evolution. This IGCP Project focussed on nine research objectives: 1) Comparison of Archean and Proterozoic supracrustal assemblages to more fully understand differences between Archean and post-Archean tectonic regimes; 2) To more fully understand the geochemical differences between Archean and post-Archean sediments and to evaluate the various factors that control sediment composition; 3) From combined U/Pb zircon and whole-rock Sm/Nd studies, to see if the apparent 2.4-2.0 continental crust "generation gap" is real; 4) To employ new techniques in the dating of individual zircons to more fully understand Proterozoic tectonic history and the role of crustal reworking; 5) From trace element ratios and Nd isotopic data from basalts, to better understand Proterozoic mantle evolution; 6) To encourage more detailed studies of the anorogenic granite-anorthosite association to better understand its origin and significance in terms of crustal evolution; 7) From combined Nd, Pb, and Sr isotopic data, to more precisely estimate the amount of new continental crust formed during the Proterozoic; 8) To encourage joint P-T and geochronological studies of Proterozoic and high-grade terranes to better understand Proterozoic orogenesis: and 9) To try and understand why hydrothermal precious metal deposits are relatively rare in the Proterozoic compared to both the Archean and the Phanerozoic. The book should be of interest to professionals in the geosciences (especially geochemists, petrologists and structural geologists) and graduate students in the same fields.