ABSTRACT Fault–fracture related “hydrothermal” carbonate reservoirs such as Albion–Scipio (Michigan) are prolific hydrocarbon reservoirs producing mainly from secondary porosity formed through hydrothermal leaching and brecciation by warm (~60°C–150°C) basinal brines. This paper, for the first time, shows that hydrothermal reservoirs may exist in the Mississippian age limestones (“Miss Lime”) of the southern midcontinent. The chapter is pivoted on the observation of a structural depression in a 3-D seismic volume from Payne County in north-central Oklahoma. The depression involves Pennsylvanian to Ordovician (and possibly deeper) units and is fully enclosed by normal faults. Overall, the fault-bounded depression appears to be a negative flower structure with its main fault extending into the basement providing a path for fluids to flow into the flower structure. Fluid inclusion studies on nearby calcite cements suggest that high-temperature brines, likely sourced from the deeper Ordovician–basement rock, have invaded the larger study area. Multiattribute inversion suggests presence of high porosity (>10%) zones in the Miss Lime depression, but confirmation of brecciation and leaching requires further studies. Nonetheless, the paper posits that several elements of a viable fault–fracture-type play are visible in the Miss Lime depression and recommends that the concept be tested along other regional basement involved faults.

ABSTRACT A succession of Ordovician and Mississippian carbonates, separated unconformably, is exposed across the southern flank of the Ozark Dome in southwest Missouri. Deposits of both periods exemplify typical facies of the Midwestern United States: carbonate tidal-flat assemblages for the Early Ordovician and carbonate shelf environments for the Early–Middle Mississippian. The basic stratigraphic sequence of these deposits has been known for over a century, but interesting features remain to be addressed. Thin discontinuous sandstones are present within the Early Ordovician Cotter Dolomite, but the informal Swan Creek sandstone member seems anomalous. This sandstone can exceed 5 m in thickness and is fairly continuous across southwest Missouri. Most Ordovician sandstones in Missouri mark major transgressions above regional unconformities, but not the Swan Creek, and there is no obvious source of the sand. Therefore, we hypothesize that the Swan Creek represents reworked eolian dunes blown across the broad peritidal environment. Clastic sandstone dikes, apparently sourced from the Swan Creek, cut across beds of Cotter Dolomite near faults. We propose that these dikes are evidence of local faulting and seismicity during the Early Ordovician. Early and Middle Mississippian limestones comprise a sequence of shelf deposits, although mud mounds and other facies changes near the Missouri-Arkansas line mark the edge of the Mississippian shelf and the transition to a ramp setting. Early Mississippian carbonate deposition was interrupted by a short and localized influx of siliciclastic sediment comprising the Northview Formation. The Northview has additional characteristics consistent with a river-dominated deltaic deposit, which we suggest as its origin. If correct, this hypothesis implies that the history of tectonic features in the Midwest is more complicated than yet known. Finally, facies changes within and between the local Mississippian formations may record an early crustal response to the impending Ouachita orogeny farther to the south.

Mississippian sedimentary facies belts in east-central California, occurring primarily in the autochthon (lower plate) of the Last Chance Thrust, are consistently oriented in a northeast–southwest direction. The boundary of one belt is marked by the depositional limit of the Osagean to Meramecian Santa Rosa Hills Limestone; a second belt farther to the northwest is bordered by the erosional truncation of the Kinderhookian to Osagean Tin Mountain Limestone. Two additional facies belts, both in the Meramecian to Chesterian Kearsarge Formation, also are present in the area; one near Jackass Flats is marked by the presence of limestone and quartzite olistoliths, and the other in the Last Chance Range includes abundant chert–pebble conglomerates. These two facies of the Kearsarge Formation also occur to the southwest at and near Mazourka Canyon in the allochthon (upper plate) of the Last Chance Thrust. The great similarity and near alignment of these facies belts in both the allochthon and the autochthon can be explained by clockwise rotation of ~55° of the allochthon around a pivot point in the west-central Inyo Mountains. In this model, displacement on the Last Chance Thrust increases from zero at the pivot point to 75 km for rocks exposed in the northern White Mountains. Reconstruction of the paleogeography suggests that the Last Chance Thrust is not part of a major fold and thrust belt but is a major structure limited to a relatively small area along the continental margin where the leading edge of an allochthonous terrane (possibly the Northern Sierra Terrane) impinged against the North American plate.