Abstract The lithological characteristics of wave- and/or storm-dominated delta-front deposits are fundamentally similar to those of facies deposited on the wave-formed shorefaces of strandplain settings. Differentiating ancient shoreface deposits from those that record deposition in proximity to contemporaneous wave-dominated deltas, therefore, is challenging, especially where the facies represent deposits that are intermediate between end-member strandplains and delta fronts. To date, archetypal facies models are inadequate to describe and distinguish between such deposits. The challenge is further accentuated where studies are limited entirely to core and other subsurface data. Depositional processes typical of deltaic settings influence infaunal organisms in subtle but significant ways. The resulting ichnological signatures clearly reflect the innate differences in physicochemical conditions and paleoenvironmental stresses operating in these settings, such as variations in sedimentation rates, substrate consistencies, oxygenation, salinities, energy conditions, increased turbidity levels, and episodic deposition associated with river floods. Lower Permian successions of the Wasp Head, Pebbley Beach, and Snapper Point Formations of the southern Sydney Basin in southeastern Australia are spectacularly exposed in extensive coastal outcrops. The preserved lithologies and many of the primary sedimentary structures are virtually identical to those characteristic of offshore and strandplain shoreface deposits. Integration of the lithological, sedimentological, and subtle ichnological differences, however, demonstrate that these units were deposited under the influence of paleoenvironmental stresses. There is also considerable evidence of very cold climatic conditions and concomitant effects on the depositional environment from ice rafting, which imposed additional paleoenvironmental stresses. For the most part, fair-weather beds closely resemble strandplain shoreface deposits, with trace-fossil suites that are very diverse and contain a mixture of structures that reflect a variety of feeding strategies characteristic of the Cruziana and Skolithos Ichnofacies. Variations in the ichnological signatures, and departures from the archetypal ichnofacies expressions, in the form of sporadic bioturbation levels, reduced assemblage diversities, and reductions in ichnogenera sizes compared to their unstressed counterparts, suggest intermittent physicochemical stresses. Associated storm deposits display many of the sedimentological and ichnological characteristics associated with river influx and deltaic conditions, including: soft-sediment deformation structures and sediment-gravity-flow deposits, recording rapid sediment emplacement; mudstone drapes that are characteristic of hyperpycnally emplaced fluid muds and rapidly flocculated muds that are produced along the zone of mixing at the base of a hypopycnal (buoyant) mud plume; unbioturbated, carbonaceous mudstone interbeds with synaeresis cracks consistent with freshet-induced salinity fluctuations; an abundance of phytodetrital material, and allochthonous wood and large logs; and sandstone beds with “stressed” trace-fossil suites attributable to the Cruziana Ichnofacies, where ordinarily suites representative of the Skolithos Ichnofacies would be expected. These characteristics suggest that fair-weather beds reflect ambient wave shoaling, but during and immediately following storms, increased river discharge strongly influenced the depositional environment and thus the characteristics of the resultant event beds. Overall, the successions are therefore interpreted as wave- and storm-dominated prodelta to proximal delta-front deposits. Variations in storm signature throughout the successions reflect temporal and spatial variations in the preservation and, therefore, abundance of fair-weather beds. Such variations may represent changing storm climates, climatic seasonality, fluctuations in river discharge, increased amalgamation of beds by persistent storm activity, subtle changes in storm tracks with respect to delta-front orientation, and subtle shallowing or deepening along the delta front.

Abstract The Walcott Quarry was discovered in 1909 by the Smithsonian Institute's Charles Doolittle Walcott (1850–1927). The Cambrian Burgess Shale (505 Ma, Miaolingian) crops out in the quarry and the lagerstätte is the nexus of ongoing vigorous debate about fossil preservation (including taphonomy and diagenesis), taxonomy, classification, phylogeny, and the origin of phyla and baupläne. Smithsonian Institute's field crews collected from 1909–24, and the quarry was subsequently expanded by Harvard University (1930), the Canadian Geological Survey (1966–67), and the Royal Ontario Museum (1992–2000). Approximately 250 000 fossils, including soft-bodied forms, have been collected, making the Walcott Quarry with exposures of the Middle Cambrian Burgess Shale, a significant geoheritage site and an important representation of the Cambrian Explosion.

Abstract West of Mississippi River natural gas, in commercial quantities, was first discovered in Miami County, Kansas, in 1877. This and subsequent supply discoveries were from rocks, mostly sandstones, of Pennsylvanian age. As most of these sandstones are lenticular, few gas occurrences are controlled by folding. It is estimated that about 350 square miles of gas-bearing rocks have been discovered since 1900. Occurrences of natural gas in rocks of Pennsylvanian age in eastern Kansas are here, for analytical purposes, divided into post- and pre-Fort Scott. The supply contributed by post-Fort Scott rocks has been small, but pre-Fort Scott rocks have been the major source of natural gas supply. The pre-Fort Scott section of Pennsylvanian rocks is divided into an upper and a lower division. The upper division, consisting of the upper 350 feet of Cherokee formation, covers all of eastern Kansas. In its upper 50 feet are found most of the gas- and/or oil-bearing shoestring sandstone bodies; in the lower part the oil-bearing sandstones of Greenwood and Butler counties. The supply of gas from these formations has not been of major importance. The lower division, with a maximum thickness of about 300 feet, contains many large sandstone bodies (also lenticular) from which natural gas was the dominant product. The important fields, producing gas from the lower division, were located in Allen, Neosho, Wilson, Montgomery, and Labette counties. They are now either abandoned or nearly exhausted. At the contact between the Pennsylvanian and Mississippian systems occurs the Burgess (Hogshooter) sandstone. This sandstone, also lenticular, is extremely erratic in distribution. Where productive, notably at Elk City in Montgomery County, it is very prolific but short-lived. Limestones in the upper 50 feet of the Mississippian system have produced gas in eastern Kansas, notably in Elk and Chautauqua counties on the Longton anticline. Rocks of Ordovician age have yielded very little gas in eastern Kansas. Occurrences of gas in post-Fort Scott rocks are up-dip accumulations, commonly found on plunging anticlines or domes. In pre-Fort Scott sandstones, the entire body may be gas-filled with bottom water, if it parallels isopach lines of the Cherokee formation, but it may be distinctly up-dip with edge and bottom waters where the body pitches with the regional dip. The upper surfaces of pre-Fort Scott sandstone bodies show structural closure (lenticularity) ; the overlying Fort Scott limestones usually show a similar structure, but the underlying Mississippian rocks are usually undisturbed excepting for regional tilting and warping. Gas-bearing areas in rocks of Mississippian age are restricted to anticlines and domes, most of which were folded and partly eroded before deposition of Cherokee sediments. The thickness of Mississippian rocks is everywhere reduced over these folds. Most of the important gas fields in Kansas were discovered and developed prior to the use of surface or subsurface geology. A few important gas fields have been found on surface structure forms, notably at Elk City in Montgomery County; a few were recognized as major subsurface folds before their importance as gas fields was known, notably the Longton anticline.

ABSTRACT Lower to Middle Cambrian strata, well exposed in imbricated westward-dipping thrust sheets of the southern Canadian Rockies, host a range of geologic features from famous fossil lagerstätten to economically important ore deposits. This paper describes six localities in the Front and Central ranges west of Calgary that record tectonic, sedimentologic, and biologic events during deposition of the lower to mid-Sauk Megasequence. At the Mount Yamnuska and Castle Mountain viewpoints, Middle Cambrian platformal carbonate sections are well exposed. These were preceded by thick, siliciclastic-dominated, shallow-marine deposits of the Gog Group, which form a dramatic geologic backdrop to Lake Louise. Farther west, a platform-to-basin facies transition is recorded in the vicinity of Field, British Columbia. Pb-Zn mineralization and dolomitization are evident near or at this facies transition at the Kicking Horse Mine in Yoho National Park, and on Fossil Ridge as seen from the Emerald Lake viewpoint. A hike to the famous Trilobite Beds of Mount Stephen offers opportunity for first-hand examination of the Burgess Shale biota and associated unusual mineralogic and geologic features including anomalously Mg-rich mudstone, carbonate mounds, and apparent syndepositional faulting, dilational cracks, brine seeps, and mud volcanism.

Abstract Bottom sediments of the largest lake of the East African Rift system, Lake Tanganyika (length 650 km; maximum depth 1470 m; volume 18,800 km 3 ) (Fig. 1), were extensively studied between 1983 and 1986 by Project PROBE of Duke University (U.S.A.) and Project GEORIFT (1984-1985) of Elf Aquitaine (France), using a wide range of methods such as reflection seismology, piston coring, and dredging. Interpretation of multifold reflection seismic profiles collected by Project PROBE suggests up to 4 km of sediment has accumulated within local depocenters. In addition, seismic profiles exhibit several seismic discontinuities and associated sequences, interpreted to have resulted from large-scale, temporal changes in local tectonics and/or climate (Burgess and others, 1988; Scholz and Rosendahl, 1988). Our interpretation of Recent and Modern profundal sediments in Lake Tanganyika is based on high-resolution, 5-kHz seismic surveys, along with multiple Kullenberg cores from the north and south basins of the lake collected during the GEORIFT project, and our interpretation of littoral clastic and biogenic sedimentation is based on grab sampling, observations from SCUBA, and gravity cores collected by the University of Arizona (Cohen, 1990; Soreghan and Cohen, 1991). These previous studies were supplemented by gravity cores collected in the Burundian part of the northern basin during a 1992 joint field operation by the University of Arizona (U.S.A.), the INSU-CNRS (France), and the CASIMIR project (Belgium). In this paper, our goal is to illustrate fundamental differences in facies associations within Lake Tanganyika that are, to a large degree, controlled by the basin structure.