The Ironside Mountain batholith consists of the 170-Ma Ironside Mountain pluton, the quartz diorite of Happy Camp Mountain, the 167-Ma Denny intrusive complex, and the West China Peak intrusive complex. The contact aureole of the Ironside Mountain pluton is present in both the western and eastern Hayfork terranes, which indicates that emplacement followed regional thrusting along the Wilson Point thrust. The batholith marks the beginning of a 15-m.y.-long episode of arc magmatism. Al-in-hornblende barometry suggests emplacement at ∼4 kb. The Denny and West China Peak complexes are predominantly gabbro to olivine pyroxenite characterized by calcic plagioclase. Along with the quartz diorite of Happy Camp Mountain, these plutons have calcic bulk compositions, abundant amphibole, and low FeO/(FeO + MgO). Their chemical and petrographic features suggest oxidized, H 2 O-rich parental magmas. In contrast, the Ironside Mountain pluton has higher FeO/(FeO + MgO), shows K 2 O enrichment with increasing SiO 2 to ultrahigh-K compositions, and is typified by 2- and 3-pyroxene assemblages in which hydrous mafic silicates are sparse or absent, except in the most evolved rocks. The elements Rb, Zr, and Ba all behave incompatibly. Initial Nd and Sr isotope ratios (170 Ma) are uniform at 87 Sr/ 86 Sr ϵ Nd of ∼5.2 and of ∼0.7037. These data suggest that the pluton lacks significant crustal input, unlike younger Middle Jurassic plutons, and that it evolved primarily by fractional crystallization of a reduced, H 2 O-poor arc tholeiite. Enrichment of K 2 O is interpreted to result from differentiation at relatively high pressure (≥8 kb), under conditions in which augite fractionation predominated over olivine fractionation. High-P fractionation without appreciable crustal input is probably related to the thermal structure of the crust. Emplacement immediately after regional thrusting placed parental magmas into cool, nonreactive host rocks. Succeeding Middle Jurassic magmatism encountered progressively hotter crust, with consequent crustal melting and assimilation.

Abstract Alluvial fans accumulate at the base of a mountain front or other upland area where an emerging mountain stream deposits a sediment body whose sloping surface forms a segment of a cone (Blissenbach, 1954; Bull, 1972a, 1977; Fig. 1). The slope of alluvial fans averages about 5º, ranging from less than a degree to as much as 25º, although rarely exceeding 10° (Denny, 1965; Bull, 1977). Where the mountain front is relatively straight, a series of adjacent alluvial fans will coalesce to form a bajada or piedmont slope (Fig. 2). The term clastic wedge has been applied to these deposits, especially where the mountain front is uplifted along faults. Ancient fan deposits may form thick complexes, are indicative of a mountainous paleogeography, and are most commonly redbeds, especially where deposited under arid conditions (Fig. 3). As channels shift laterally through time, the sedimentary body develops a characteristic fan shape in plan view, a convex-upward cross-fan profile, and concave-upward radial profile (Fig. 4). Radial profiles permit subdivision of fans into upper, middle, and lower segments (Fig. 5). Small bodies more steeply sloping that were deposited by small streams may be referred to as alluvial cones rather than fans; these may grade into scree or talus cones deposited by falling debris rather than stream transport. Fan-deltas are alluvial fans deposited into standing bodies of water (Fig. 1F); their distal facies,

Abstract Dennis Curry was a most successful businessman and a generous philanthropist. He also led a double life as a geologist and palaeontologist. This appreciation of the man and the scientist is supported by recollections of two of his former colleagues at University College London, where he was Visiting Professor of Marine Geology. This is followed by a bibliography of approximately 130 geological papers on a range of topics - mirroring his wide interests - that he published either singly or co-authored over a 62-year period.

Abstract The central Piedmont of South Carolina includes two terranes derived from Neoproterozoic peri-Gondwanan arcs and one that preserves the Cambrian Series 2–Series 3 Carolinian Rheic rift-drift sequence. These are the Charlotte, Silverstreet and Kings Mountain terranes. The central Piedmont shear zone juxtaposes each of these terranes against the Late Silurian Cat Square paragneiss terrane. The Kings Mountain terrane is composed of meta-epiclastic rocks with distinctive metaconglomerate horizons, manganiferous formation, meta-sandstones, and dolomitic marbles. One of the lower metaconglomerate horizons yields detrital zircons of latest Middle Cambrian age. This stratigraphy is interpreted to record the Rheic rift-drift sequence on the trailing edge of an Ediacaran-Cambrian arc terrane as it pulled away from the Amazonian craton in Middle Cambrian–Furongian time. The Charlotte terrane records magmatic activity from before 579 ± 4 until ∼535 ± 4 Ma. Mafic-ultramafic zoned intrusive complexes intruded mafic-ultramafic volcanic piles. Ultramafic dikes cut the volcanic rocks and are interpreted as feeders to stratigraphically higher levels of volcanism. These mafic to ultramafic rocks record arc rifting resulting from subduction of a spreading ridge or bathymetric high. These rocks were metamorphosed to amphibolite facies at about the time of the Cambrian–Precambrian transition. The Silverstreet terrane preserves relict medium temperature eclogites and high-pressure granulites in the lower plate (Charlotte terrane) of an arc-arc collision. Relict high-pressure assemblages record 1.4 GPa, 650–730 °C conditions. High-pressure mineralogy and textures are best preserved in the cores of boudins derived from dikes with Ti-V ratios of 20–50 (i.e., MORB). High-pressure metamorphism may have occurred in Ediacaran-Cambrian time, and must have occurred prior to the intrusion of the 414 ± 8 Ma Newberry granite. The Cat Square basin contains detrital zircons as young as 430 Ma, accepted detritus from both Laurentia and Carolinia, and so is interpreted as a successor basin. The Cat Square terrane underwent peak (upper amphibolite-granulite) metamorphic conditions at the time of the Devonian–Mississippian transition while it was at the latitude of the New York Promontory. The peri-Laurentian-Carolinian suture is either buried under the Blue Ridge Piedmont thrust sheet or was thrust up and eroded away. The central Piedmont shear zone is a younger feature, no older than Visean.

Abstract Eight stops on a one-day field trip along the Savannah River corridor between Plum Branch, South Carolina, and Augusta, Georgia, review the Ediacaran–Cambrian and Pennsylvanian–Permian history of several terranes that comprise Carolinia in the eastern Piedmont. The foliation of ca. 550 Ma andesitic metatuffs of the Persimmon Fork is isoclinally folded. This event may be related to other recognized events in Carolinia at the Cambrian-Precambrian boundary or the folding of the sub–Asbill Pond angular unconformity before the intrusion of the Clouds Creek pluton. Three stops illustrate features of the Modoc zone in the eastern Piedmont. Variably mylonitized Modoc zone orthogneisses were intruded between 300 and 310 Ma. Mylonitic Modoc zone orthogneisses are parasitically folded around the northwest-vergent Kiokee antiform. Monazites from the core of the Kiokee antiform yield TIMS (thermal ionization mass spectrometry) U-Pb ages of ca. 306–308 Ma, and hornblende yields 40 Ar/ 39 Ar plateaus of ca. 288 and 296 Ma. Favorably oriented near-vertical segments of the steeply dipping to overturned limb of the Kiokee antiform are reactivated with dextral strike-slip sense and locally preserve spectacular composite planar fabric. The serpentinites at Burks Mountain include serpentinized orthopyroxene and chromite. The origin of these ultramafic rocks may have been at the base of an ophiolite or an ultramafic layered intrusion in the lower continental crust. The ca. 294 Ma Appling granite is undeformed and intrudes the trailing limb of the Kiokee antiform. The Augusta fault frames the southeastern margin of the Kiokee belt schists and gneisses. The fault is known from a single quarry exposure that places low-grade metavolcanics and epiclastic rocks in the hanging wall against footwall gneisses and schists of the Kiokee belt. The most distinctive rocks in the quarry are K-silica-metasomatized mylonites interleaved with chlorite schists. The origin of K and Group I cations is thought to be the retrogression of biotite. Furthermore this metasomatism is thought to have accompanied Triassic rifting. These metasomatic effects are heterogeneously developed in the footwall Kiokee belt gneisses, and are well known in the footwall of the Triassic border fault of the Dunbarton basin, underlying the U.S. Department of Energy (DOE) Savannah River Site. It is thought that no differential rotation of the eastern Piedmont in this area occurred after ca. 275 Ma. A final stop is made to observe the low-grade metavolcanic rocks of the Belair belt south of the Augusta fault.