Fossil birds are relatively rare in Cretaceous deposits of the Northern Great Plains, so the discovery of a large, new diving bird was unexpected. From marine deposits of the Niobrara Formation in Kansas a small diversity of birds was known, but until now the large diving bird, Hesperornis , was the only bird taxon known from the Pierre Shale Group of South Dakota. The new discovery, a partial skeleton of another diving bird, Baptornis , was secured from the Sharon Springs Formation (lower middle Campanian) of the Pierre Shale Group in Fall River County, South Dakota. The specimen is represented by vertebrae, pelvic fragments, and lower leg elements that are similar to but much more robust than Baptornis advenus from the subjacent Niobrara Formation. The new taxon is nearly twice the size of the Niobrara species, principally in robustness rather than in length of elements. Overall, the specimen represents the first occurrence of Baptornis from the Pierre Shale Group, represents a new species, and indicates a greater diversity of birds from the Pierre Shale Group than was previously known.

A zone of intense soft-sediment deformation, with associated spherules and shocked quartz grains, is identified over an area of ∼1000 km 2 in southwestern South Dakota. This Disturbed Zone (DZ) is up to 5 m thick and is preserved within distal deltaic deposits of the Upper Cretaceous Fox Hills Formation. Localized structural development caused thinning and eventual subaerial exposure of several sections within Badlands National Park, whereas sections to the north of the park were unaffected. Although previously interpreted as an intense period of soil formation under tropical conditions, the degree of ancient soil overprinting of these sections is minimal, with the exception of bright coloration of the strata, and appears not to have had any effect on ejecta preservation. Biostratigraphic data suggest a middle to late Maastrichtian age for the DZ. When compared to other Cretaceous impactites, our study sections in southwestern South Dakota are most similar to, and may correlate with, the recently documented 68 Ma impactite within the Vermejo Formation of Berwind Canyon in southeastern Colorado. If this correlation is correct, the size of the ejecta within the Fox Hills and Vermejo Formations suggests that the sections in South Dakota represent distal deposits.

Abstract The southern flank of the Black Hills uplift is characterized by high geothermal gradients, which exceed 40°C/km at many places and attain a maximum estimated value of 84°C/km. Aeromagnetic, gravity, geologic, geothermal, and Na-K-Ca-Mg geother-mometer data are correlated to attempt to understand better the geothermal system of the upper crust of this region. Analyses of the gravity and magnetic fields include compilation of derivative maps to enhance the expressions of lithologic and structural boundaries. In our model of the geothermal system of the southern Black Hills, ground waters in the topographically high areas descend to a depth of roughly 1.6 km along southward- and southeastward-trending fault zones, migrate upward primarily along faults after becoming heated, and spread outward through permeable sedimentary units. Several interpreted gravity and magnetic features appear to be related to the structural control of the thermal convection. For example, fault-formed lithologic boundaries expressed in the gravity and magnetic data may act as conduits for the southeastward-trending ground waters. These boundaries are abruptly truncated at their southeastern edges by northeast-trending features that presumably represent fault zones. Thermal gradients are significantly higher southeast of the northeast-trending fault zones. Of particular interest are two broad structures, an antiform and a basin, that appear to influence the channeling of warm water.

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Abstract One of the most famous and spectacular Tertiary deposits in North America is the White River Badlands. The colorfully banded, fossiliferous, highly dissected landscapes are exposed across much of southwestern South Dakota; a specific landmark is difficult to designate. Most visitors to the Badlands traverse the area in the Badlands National Park between the towns of Interior and Wall in Pennington and Jackson Counties (Fig. 1). Most geological features may be viewed along South Dakota 240, the Badlands Loop; therefore this area has been designated a landmark. Geology is well-exposed along the route at such localities (Fig. 1) as the Pinnacles, Yellow Mounds, Rainbow Overlook, Banded Buttes Overlook, and Cedar Pass. Due to space limitations herein, frequent references are made to the road log, photographs, and bibliographic references of the area by Martin (1985).