The Appalachians are a Paleozoic orogen that formed in a complete Wilson cycle along the eastern Laurentian margin following the breakup of supercontinent Rodinia and the coalescence of all of the continents to form supercontinent Pangea. The Appalachian Wilson cycle began by formation of a Neoproterozoic to early Paleozoic rifted margin and platform succession on the southeastern margin of Laurentia. Three orogenies ultimately produced the mountain chain: the Ordovician Taconic orogeny, which involved arc accretion; the Acadian–Neoacadian orogeny, which involved north-to-south, transpressional, zippered, Late Devonian–early Mississippian collision of the Carolina superterrane in the southern-central Appalachians and the Avalon-Gander superterrane in the New England Appalachians, and Silurian collision in the Maritime Appalachians and Newfoundland; and the Alleghanian orogeny, which involved late Mississippian to Permian collision of all previously formed Appalachian components with Gondwana to form supercontinent Pangea. The Alleghanian also involved zippered, north-to-south, transpressional, then head-on collision. All orogenies were diachronous. Similar time-correlative orogenies affected western and central Europe (Variscan events), eastern Europe and western Siberia (Uralian events), and southern Britain and Ireland; only the Caledonide (Grampian–Finnmarkian; Caledonian–Scandian) events affected the rest of Britain and the Scandinavian Caledonides. These different events, coupled with the irregular rifted margin of Laurentia, produced an orogen that contains numerous contrasts and nonthroughgoing elements, but it also contains elements, such as the platform margin and peri-Gondwanan elements, that are recognizable throughout the orogen.

Abstract DNAG Transect E-3. Part of GSA’s DNAG Continent-Ocean Transect Series, this transect contains all or most of the following: free-air gravity and magnetic anomaly profiles, heat flow measurements, geologic cross section with no vertical exaggeration, multi-channel seismic reflection profiles, tectonic kindred cross section with vertical exaggeration, geologic map, stratigraphic diagram, and an index map. All transects are on a scale of 1:500,000.

Seismic reflection profiles and SeaMARC II imagery from the southwest Panama margin demonstrate that oblique convergence is presently occurring along what had previously been thought of as a transform margin. Our seismic profiles image landward-dipping thrust faults and seaward-verging folds at the toe of the slope. The frontal deformation zone as imaged on the SeaMARC II mosaic is 12 to 15 km wide with individual east-west-trending folds and thrusts that are laterally continuous for 5 to 10 km. Much of the terrigenous trench sediment is offscraped and accreted, forming an accretionary prism (South Panama deformed belt). Three linear ridges (part of the Panama Fracture Zone complex) are being obliquely subducted along the southwest Panama margin. The oblique convergence causes the ridges to sweep eastward along the trench. The SeaMARC II mosaic shows that the regional structure of the South Panama deformed belt is dominated by east-west-trending trench segments that are separated by the north-south fracture zone ridges. The trench shallows where the ridges intersect the trench, and the deformation front is warped around the ridges. On the east side of each ridge the accretionary complex bends to a northwest-southeast trend, suggesting that the ridges are deforming the accretionary complex. As the accretionary prism rides up over each ridge, it thickens markedly. By the time the prism reaches the top of the ridge, its surface slope has been greatly oversteepened and large portions of accreted material slump into the trench. After passage of the ridge, the system returns to its “normal” state, and accretion resumes, adding the slumped material back into the accretionary prism. The accretionary prism is thus only temporarily disrupted by the subduction of the Panama Fracture Zone system ridges.

Abstract The Stress Map of North America , constructed on four 42 inch by 55 inch sheets, plots modern maximum horizontal stress (SHmax) orientations for North America inferred from a variety of geophysical and geologic data. These data are described and discussed in the companion DNAG volume Neotectonics of North America. A brief description of the various stress indicators is given in the legend.

Abstract DNAG Transect A-3. Part of GSA’s DNAG Continent-Ocean Transect Series, this transect contains all or most of the following: free-air gravity and magnetic anomaly profiles, heat flow measurements, geologic cross section with no vertical exaggeration, multi-channel seismic reflection profiles, tectonic kindred cross section with vertical exaggeration, geologic map, stratigraphic diagram, and an index map. All transects are on a scale of 1:500,000.

Abstract The Gulf of California is an excellent laboratory for studying sedimentary processes on time scales that are not resolvable in the open ocean. The high biological productivity and the unique physical character of the gulf combine to produce sedimentological processes that preserve annual phenomena. This volume is organized into six sections. Part 1 covers historical exploration of the area. Part 2 includes 5 chapters detailing information contained on the 5 fold-out maps that accompany the volume. Part 3 consists of chapters on regional geophysics and geology. Part 4 covers satellite geodesy. Part 5's seven chapters discuss physical oceanograpy, primary productivity, and sedimentology. Part 6 covers hydrothermal processes.

Abstract The 10 papers contained in this publication are oriented toward the hydrocarbon potential of Antarctica. Contents include regional seismic surveys involving tectonic and stratigraphic interpretations extending from the Adelie Coast margin, over the Ross Sea and Bellingshausen Sea, throughthe Bransfield Straight and along the northern Antarctic Peninsula. Mesozoic sedimentary basins are compared in detail, and a tectonic synthesis of Antarctica and the surrounding southern seas is presented.

Abstract DNAG Transect C-1. Part of GSA's DNAG Continent-Ocean Transect Series, this transect contains all or most of the following: free-air gravity and magnetic anomaly profiles, heat flow measurements, geologic cross section with no vertical exaggeration, multi-channel seismic reflection profiles, tectonic kindred cross section with vertical exaggeration, geologic map, stratigraphic diagram, and an index map. All transects are on a scale of 1:500,000.