The Talladega belt in Alabama and Georgia is the northwesternmost belt of the Appalachian Piedmont metamorphic province. It contains low-rank metasediments and metavolcanics that have been thrust faulted onto Paleozoic sediments of the Valley and Ridge province via the Cartersville-Talladega fault system. The age of several formations in the southwestern part of the Talladega belt in Alabama has been determined to be Devonian, but controversy exists concerning the age of much of the rest of the belt. Another major problem has been the age and structure relationships of the Talladega belt to the Precambrian and Lower Cambrian rocks of the Blue Ridge province on strike with the Talladega belt to the northeast. In the Borden Springs area, Cleburne County, Alabama, nappes of the Lower Cambrian Weisner and Shady Formations rest on younger Paleozoic rocks immediately northwest of the Talladega belt. A sequence composed mainly of slates and quartzites characterized by graded beds lies between the Talladega belt and the nappes of Weisner and Shady. Distinctive lithologies within this sequence are found also within the Talladega belt near Borden Springs and also near the southwest end of the belt in Alabama within metasediments immediately below the Jumbo Dolomite of the Sylacauga Marble Group. Although the slate-quartzite sequence has been interpreted in recent years as being Ordovician to Devonian, detailed mapping in the Borden Springs area indicates that it is correlative with the Early Cambrian Weisner and Shady, although somewhat different in sedimentary aspect from Weisner and Shady in nappes to the west. Therefore, the Talladega belt may contain rocks at least as old as Early Cambrian and may be at least partly equivalent in age to rocks of the Blue Ridge province. The slate-quartzite sequence lies northwest, west, and southeast of an anticlinal region of younger Paleozoic sediments in western Georgia, over which it was thrust faulted. It thus forms an imbricated nappe sequence rooted, if at all, beneath the Piedmont province to the southeast.

ABSTRACT Correlations of Paleozoic strata from the southern Appalachian, Black Warrior, and Ouachita-Arkoma forelands show varying lithofacies and stratigraphic thicknesses for coeval deposits, as well as differences in the location of disconformities. This field trip will visit stops throughout the Ouachita Mountains and Arkoma basin to observe clastic strata variability in the Cambrian, Ordovician–Silurian, Mississippian, and Pennsylvanian periods. The spatial-temporal relationship between these units provides a first-order understanding of orogenic processes along the southeastern and southern Laurentian margin during the amalgamation of the supercontinent Pangea. We present a summary of detrital zircon geochronology from the three foreland systems and correlative stops in the Ouachita Mountains to discuss sediment provenance, paleo-reconstructions, and to identify needed geochronology information for future studies. Cambrian through Devonian units in the southern Appalachian foreland of Alabama and Ouachita thrust belt are dominated by Proterozoic Grenville (1250–900 Ma) and Granite-Rhyolite (1550–1300 Ma) province grains, with minor Archean grains. Mississippian and Pennsylvanian units in the southern Appalachian and Ouachita-Arkoma forelands exhibit similar age spectra and are primarily characterized by a dominant Grenville peak, alongside smaller Appalachian (490–270 Ma), Granite-Rhyolite, Yavapai-Mazatzal (1800–1600 Ma), and Wyoming (>2400 Ma) peaks. Proportional differences in the age spectra can be identified when comparing individual stratigraphic intervals in the forelands, and have been interpreted to represent influxes of different drainage systems associated with along strike versus perpendicular sediment routing. Mississippian strata in the Ouachita Mountains, Arkoma basin, and Black Warrior basin exhibit unique age spectra in comparison to other Ouachita and southern Appalachian signatures. A dominant Appalachian peak (<480 Ma), alongside smaller Grenville, Granite-Rhyolite, Yavapai-Mazatzal, and Wyoming peaks identified in the Batesville Sandstone of the Ouachita-Arkoma foreland, suggests a possible connection to barrier island depositional systems to the east. Pennsylvanian strata in the Black Warrior basin exhibit similar age spectra to those of samples from the southern Appalachian and Ouachita-Arkoma forelands.

The three southernmost external Appalachian Grenville basement massifs occur in the Georgia western Blue Ridge, where they core map-scale, inclined-to-recumbent, west-vergent isoclinal anticlinoria formed during peak greenschist-facies Paleozoic metamorphism. The massifs are in thrust contact with Cambrian rocks of the adjacent foreland thrust belt. The basal cover unit of each massif, the Pinelog Formation, is likely correlative with the Late Proterozoic Snowbird Group of the Ocoee Supergroup. This sequence was deposited in fluvial-alluvial to shallow-water deltaic to intertidal environments adjacent to sharp basement uplifts, most probably along extensional fault scarps during initial Late Proterozoic rifting of Laurentia. A second phase of more extensive continental rifting and subsidence followed with deposition of the Great Smoky Group, a mostly deep-water turbiditic sequence. During the second rift cycle, a large (>2000 km 2 ) block, which included much of the Georgia western Blue Ridge and contained the deposits of the earlier rift basin, was tilted westward with the underlying basement along a southeast-dipping extensional fault system (stratigraphic offset >1 km) flanking the western margin of the Blue Ridge. Great Smoky units lie unconformably above this block and progressively cut deeper into the underlying cover sequence and then into the basement toward the east. This northwest-border fault system was bounded to the southwest by a large continental transfer (transform) fault, which marked the southern limit of the Ocoee basin, and across which the polarity of faulting along the rifted margin was reversed. Internal thrusts associated with Alleghanian continental collision, e.g., the frontal Blue Ridge thrust, were likely rooted below the basement massifs because the massifs had been previously detached from autochthonous basement by the two earlier cycles of rift-related faulting.

Abstract The allochthonous Talladega belt of eastern-northeastern Alabama and northwestern Georgia is a northeast striking, fault bounded block of lower greenschist facies metasedimentary and metaigneous rocks that formed along the margin of Laurentia at or outboard of the seaward edge of the Alabama promontory. Bounded by metamorphic rocks of the higher grade Neoproterozoic(?) to Carboniferous eastern Blue Ridge on the southeast and unmetamorphosed to anchimetamorphic Paleozoic rocks of the Appalachian foreland on the northwest, the Talladega belt includes shelf facies rocks of the latest Neoproterozoic/earliest Cambrian Kahatchee Mountain Group, Cambrian-Ordovician Sylacauga Marble Group, and the latest Silurian(?) to uppermost Devonian/earliest Mississippian Talladega Group. Along the southeastern flank of these metasedimentary sequences, a Middle Ordovician back-arc terrane (Hillabee Greenstone) was tectonically emplaced along a cryptic pre-metamorphic thrust fault (Hillabee thrust) and subsequently dismembered with units of the upper Talladega Group along the post-metamorphic Hollins Line fault system. Importantly, strata within the Talladega belt are critical for understanding the tectonic evolution of the southern Appalachian orogen when coupled with the geologic history of adjacent terranes. Rocks of the lower Talladega Group, the Lay Dam Formation, suggest latest Silurian–earliest Devonian tectonism that is only now being recognized in other areas of the southern Appalachians. Additionally, correlation between the Middle Ordovician Hillabee Greenstone and similar bimodal metavolcanic suites in the Alabama eastern Blue Ridge and equivalent Dahlonega Gold belt of Georgia and North Carolina suggests the presence of an extensive back-arc volcanic system on the Laurentian plate just outboard of the continental margin during the Ordovician and has significant implications for models of southern Appalachian Taconic orogenesis.

Abstract The Knox Group in the Black Warrior Basin comprises the southeastern part of the great American carbonate bank (GACB) and consists mostly of carbonates. The Black Warrior Basin is a Carboniferous foreland downwarp developed over a passive margin of early Paleozoic age. Similar to other parts of the GACB, the thick widespread Cambrian–Ordovician Knox Group was deposited as mostly shallow-water, restricted, marine carbonates. The Knox depositional model is that of an extensive regressive tidal flat, made up of shallow subtidal, intertidal, and rare supratidal facies. These facies shallow upward and comprise numerous cycles in the Knox. There exists a tremendous variation in thickness of the cycles that can be as thin as 3 to more than 100 ft (1 to >30 m) thick. These cycles can be further grouped into packages of sequences that are mostly composed of intertidally dominated or subtidally dominated cycles. Large-scale regional changes in relative sea level may have a large influence on the type of cycles and sequences that formed during the Knox. Knox strata, especially within third-order sequence boundaries, are correlatable across the basin. Detailed local to regional correlation of the facies bundles can be made with gamma-ray and resistivity logs; however, facies are commonly obscured by strong diagenetic overprints that make detailed correlation difficult. Numerous unconformities occur within the Knox Group at major sequence boundaries. The super-Knox unconformity is recognized as evidence of a globally eustatic sea level drop and has been used to mark the boundary between the Sauk and Tippecanoe depositional megasequences. Paleokarst is observed regularly within the Knox carbonates, especially along major sequence boundaries with related unconformity surfaces. Paleokarstic features in the Knox Group have been identified in outcrop in central Alabama, with the Knox containing a sinkhole filled with Middle Ordovician strata. Numerous cores contain collapse breccias that are interpreted to have formed in response to karst conditions. With some paleokarst collapse breccias occurring 3000ft (914 m) below the top of the Knox, itislikely that some of these breccias formed in response to intra-Knox unconformities. In the Knox, diagenetic changes are a continuum that begins with early diagenesis, including hypersaline or evaporative, vadose, and phreatic conditions, and followed by deep phreatic to late thermal diagenesis. Evidence exists that porosity formed (some of which may be thought of as karst) during each of these diagenetic phases. Conversely, precipitation events and dolomitization also occurred throughout various levels of the profile. Volumetrically, dolomite is the most abundant mineral. Knox dolomite can be subdivided into early (syngenetic to penecontemporaneous) hypersaline dolomite, shallow burial mixed-water (phreatic) dolomite, and deeper burial to thermal (baroque and xenotopic) dolomite. Reservoir development is typically along sequence boundaries, especially where facies have strong diagenetic overprints from dolomitization and dissolution associated with paleokarstic events. The best reservoirs are structurally related, with strong fracture overprints.

Abstract Tephra deposits in the deep sea can survive undisturbed for long periods of time and, on regional scales, tend to be much better preserved than their subaerial counterparts. In this study, grain size distributions and thicknesses of tephra deposits from the Campanian Ignimbrite (CI) eruption (39 000 yr BP; magnitude c. 7.7) preserved in thirty-three deep sea cores are analysed to infer key eruption parameters. Distal deep sea tephra thickness data show an exponential decrease with distance from source. Such trends are difficult to identify in distal subaerial data owing to reworking and limited exposure. We find that tephra grain size distributions are much less affected by depositional environment than thickness, with trends that are consistent across distal subaerial, lacustrine and deep sea environments. The CI layer exhibits bimodal grain size distributions to distances of c. 1000 km, after which it becomes unimodal. Such trends can be related to different mechanisms of tephra transport in the atmosphere, whereby at proximal to medial distances the Plinian and co-ignimbrite phases produce distinct plumes. Within 150 and 900 km from source, Plinian tephra constitutes 40±5% of the deposit volume. Beyond this region where coarse particles are deposited, the plumes merge and fines derived largely from co-ignimbrite elutriation are spread in the atmosphere at velocities greater than the settling velocities of the particles.

Abstract By the decade of the 1960s, the public was certain that science and technology could provide the answers to most of the world’s problems. To be sure, between 1900 and 1964, the average life expectancy had risen from 49 years to 70 years. In addition, a broad spectrum of new wonders were available—transistor radios, television, jet aircraft, artificial fibers, plastics, unusually high crop yields, and cheap electricity produced from nuclear power and low-priced oil from overseas. Consequently, scientific leaders were proud of their accomplishments and the presence of strong public support. As Dr. Donald Hornig, Science Advisor to President Nixon, observed (Hornig, 1965): Our federal expenditures (for research and development) have increased some two hundred times since the beginning of World War II. Put differently, the size of the effort has doubled every seven years, measured in dollars, or every twelve years, measured in numbers of people engaged. 2 For scientists and engineers, the 1960s were truly a golden age. If you conceived something new, its development was likely to be funded. In sharp contrast to Dr. Hornig’s optimistic report cited above, the economic and technical problems facing the petroleum industry in the late 1950s continued right into the 1960s. In fact, the Society of Exploration Geophysicists (SEG) lost membership (under three percent) between 1960 and 1963. Within the United States, the number of seismic land crews fell from about 380 in 1960 to a low of 190 in 1970. Oil from Venezuela, North Africa, and the Middle East was