Sulfuric Acid Speleogenesis of Carlsbad Cavern and Its Relationship to Hydrocarbons, Delaware Basin, New Mexico and Texas (1)
CAROL A. HILL
AAPG Bulletin
Volume 74, Issue 11. (November), Pages 1685 - 1694 (1990)

Sulfur-isotope data and pH-dependence of the mineral endellite support the hypothesis that Carlsbad Cavern and other caves in the Guadalupe Mountains were dissolved primarily by sulfuric acid rather than by carbonic acid. Floor gypsum deposits up to 10 m thick and native sulfur in the caves are significantly enriched in {32}S; (isotope){34}S values as low as -25.8 per mil (CDT) indicate that the cave sulfur and gypsum are the end products of microbial reactions associated with hydrocarbons. A model for a genetic connection between hydrocarbons in the basin and caves in the Guadalupe Mountains is proposed. As the Guadalupe Mountains were uplifted during the late Pliocene-Pleistocene, oil and gas moved updip in the basin. The gas reacted with sulfate anions derived from dissolution of the Castile anhydrite to form H[2]S, CO[2], and "castile" limestone. The hydrogen sulfide rose into the Capitan reef along joints, forereef carbonate beds, or Bell Canyon siliciclastic beds and there reacted with oxygenated groundwater to form sulfuric acid and Carlsbad Cavern. A sulfuric-acid mode of dissolution may be responsible for large-scale porosity of some Delaware basin reservoirs and for oil-field karst reservoirs in other petroleum basins of the world. "

ABSTRACT
Hypogene speleogenesis is widespread throughout the Delaware Basin region as evidenced by intrastratal dissolution, hypogenic caves and suites of diagenetic minerals. The world famous carbonate caves of the Capitan reef facies of the Guadalupe Mountains have long been associated with sulfuric acid processes and recently have been associated with semi-confined, hypogene dissolution. However, evaporite karst within Permian
backreef and basin-filling facies has been traditionally associated with surficial, epigene processes. On the eastern edge of the Delaware Basin cavernous porosity associated with
oil reservoirs in Permian carbonates have been attributed to eogenetic karst processes. Interbedded (evaporite / carbonate), backreef facies within the Seven Rivers Formation exhibit characteristics of hypogene dissolution associated with semi-confined dissolution controlled by the eastward migration and entrenchment of the Pecos River. Coffee Caves is a classic example of hypogene dissolution, forming a multi-storey,
rectilinear maze with abundant morphologic features suites (i.e. risers, channels and
cupolas) indicative of hypogene speleogenesis. Other caves within the Seven Rivers and Rustler Formations show similar patterns, yet often less developed. Within the Delaware Basin, Castile Formation evaporites have been extensively modified by hypogene processes. Field mapping coupled with GIS analyses clearly shows karst development and evaporite calcitization are highly clustered throughout the outcrop area. Individual caves commonly exhibit complex morphologies, including
complete suites of morphologic features indicative of intrastratal dissolution. Clusters of hypogene caves are commonly associated with clusters of evaporite calcitization and often occurrences of secondary selenite bodies, suggesting all three are genetically
related. Brecciated cores and associated native sulfur deposits indicate that calcitized occurrences are the result of semi-confined sulfate reduction in the presence

A lost arc–back-arc terrane of the Dunnage oceanic tract recorded in clasts from the Garin Formation and McCrea mélange in the Gaspé Appalachians of Québec
Céline Dupuis1,{dagger}, Michel Malo1,*, Jean Bédard2,§, Bill Davis3 and Mike Villeneuve

Upper Ordovician Garin conglomerates (base of the Gaspé belt, Québec Appalachians) contain three igneous clast populations. (1) Calc-alkaline intermediat-felsic rocks resemble Exploits (New Brunswick, Maine) and Notre Dame (Québec, Newfoundland) subzone lavas. Clasts (monzonite-rhyodacite) give U-Pb zircon ages between 465 and 466 Ma, precluding correlation with Exploits rocks. We suggest that the suite represents peri-Laurentian continental arc magmas coeval with the Red Indian Lake Group of Newfoundland. Correlation of lavas from a Gaspé well with the Popelogan arc implies that the Red Indian Line passes through southern Gaspé. (2) Mafic tholeiitic-to-alkaline clasts resemble New Brunswick and Maine (Exploits subzone) alkaline lavas. We interpret them as magmas associated with initiation of a back-arc basin, possibly on the Laurentian margin. (3) Mafic-intermediate tholeiitic to calc-alkaline clasts have an oceanic subduction component and correlate with Notre Dame subzone lavas (Québec, Newfoundland). They are interpreted as products of spreading and off-axis magmatism of a peri-Laurentian back-arc basin. We correlate McCrea mélange lavas to the calc-alkaline intermediat-felsic and mafic-intermediate suites and interpret them as samples of a Notre Dame subzone terrane coeval with the Red Indian Lake Group of Newfoundland during initiation of a successor arc–back-arc, a terrane which is no longer preserved in New Brunswick and Maine but that provides some evidence for possible extensions of Newfoundland's geology into the Gaspé Appalachians of Québec. A mid-ocean-ridge basalt–like intrusion in the McCrea mélange (Ar-Ar age: 471.2 ± 11.2 Ma) is coeval with peri-Laurentian ophiolites in Newfoundland and may record a back-arc opening event.

Key Words: igneous clasts • cal

The study of lake sediments as recorders of past climate change has been a major focus of the Geologic Division's Global Change and Climate History Program. In particular, lakes of the Upper Mississippi Basin (UMB) provide some of the most detailed records of climate and environmental change during the Holocene (last 10,000 years). The UMB is particularly sensitive to climate change because the three airmasses that control the climate of North America (fig. 1) intersect here.