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Eocene shelf-slope clinoforms on Spitsbergen reflect asymmetric basin infill across the coastal plain, shelf, slope, and deepwater segments of a foreland basin. Although four main types of clinoforms are recognized in the basin, this study focuses on clinoforms generated by a storm-wave regime on the shelf margin. The key aspect of this type of clinoform (Type 3) is that only modest volumes of sand were delivered across the shelf edge onto the slope, and little or no sand onto the basin floor, despite the sand-prone nature of the sediment delivery system, right to the shelf edge. The sedimentology and geometry of a series of such clinoforms are documented along a continuously exposed outcrop transect, some 800 m high and 4 km long. Sandstone units of individual clinoforms are 2-12 m thick, and are separated by thicker shale. Clinothems have subhorizontal ''topset'' and ''bottomset'' segments and steeper mid-portions, and are up to 150 m high, nearly an order of magnitude higher than the deltas and shorefaces that constructed them. This clinoformal configuration is thus interpreted to reflect shelf, shelf-edge, slope, and base-of-slope depositional environments, and water depths at least as great as the decompacted clinoform amplitudes. Exposed shelf segments dip up to 0.4 degrees whereas slope segments (some 2150 m wide) dip up to 4 degrees. The shelf and upper-slope reaches of clinothems consist of hummocky and swaly cross-stratified sandstone units without any significant interbedded shale. On the middle slope and below, these sandstone units become finer grained, are ripple-and plane-parallel laminated, and separated with interbedded shale. Individual ''topsets'' of clinothems are interpreted to have formed by strandplain or wavedominated delta progradation across the morphological shelf platform during short periods of sea-level stillstand or slight fall. The shale units immediately above sandy clinothems developed during longer intervals of relative sea-level rise, when the wave-dominated shoreline retreated back across the shelf platform. The long-term trajectory of shelf-margin growth shows a significant aggradational component during overall progradation. Compared to other clinoforms in this same basin where the sediment-delivery system was fluvially driven and brought great volumes of sand onto the basin floor and slope, respectively, stormwave-generated clinoforms brought only limited sand to the upper slope and little or no sand to the basin floor.

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New geologic mapping and tephrochronologic assessment of strata in extensional basins surrounding Knoll Mountain (Nevada, USA) reveal a geologic history linked to tectonic development of the Yellowstone hotspot and Snake River Plain to the north, and to the Ruby-East Humboldt-Wood Hills metamorphic core complex to the south. Data from these areas are utilized to present a paleogeographic reconstruction of northeastern Nevada-southcentral Idaho depicting the architecture of extensional faulting and basin development during collapse of the Nevadaplano over the past 17 m.y.Knoll Mountain is a northeast-trending horst along the southern margin of the Snake River Plain and track of the Yellowstone hotspot. The horst is bounded on the east by the Thousand Springs fault system and basin, and on the west by the Knoll Mountain fault and basin, where streams currently drain north into the Snake River Plain. The Knoll and Thousand Springs basins form half-grabens that are filled with the ca. 16 Ma to ca. 8-5 Ma Humboldt Formation, which was deposited in alluvial, eolian, and lacustrine environments during slip along range-bounding faults and a series of late-stage synthetic intrabasin faults. Structural, chronologic, and sedimentologic assessment of the Humboldt Formation in the Knoll basin indicates that it records overall southward fluvial drainage with slip along the Knoll Mountain fault beginning ca. 16 Ma and continuing to at least 8 Ma, and that between 8 and ca. 5 Ma, a west-dipping intrabasin fault system had developed. Between ca. 8-5 Ma to ca. 3 Ma, several fundamental changes took place, beginning with the cessation of faulting followed by widespread erosion that in turn was followed by deposition of older alluvium. The reversal of drainage direction from south to north flowing in the Knoll basin also took place during this time period, but its age relative to the widespread erosion or older alluvium is unknown.An integration of our work with previous studies north of Knoll Mountain reveal that the Knoll Mountain and intrabasin faults terminate to the north in the vicinity of the Jurassic Contact pluton, and that this area forms an accommodation zone separating broadly coeval and colinear faults bounding the ca. 10-8 Ma north-trending Rogerson graben, the northern end of which merges with the Snake River Plain. Furthermore, an integration of our work with previous work south of Knoll Mountain reveals that the Knoll Mountain fault formed part of a >190-km long, west-dipping fault zone that included the Ruby-East Humboldt detachment. This fault zone, which we refer to as the Knoll-Ruby fault system, had an extensive hanging-wall basin, the KnollRuby basin. The Knoll-Ruby fault system was a prominent structure facilitating collapse of the Nevadaplano in northeastern Nevada between ca. 16 and ca. 8-5 Ma, and its central part produced partial exhumation of high-grade, mid-crustal metamorphic rocks in the Ruby-East Humboldt-Wood Hills metamorphic core complex. By 8-5 Ma, during the waning stages of extension a...

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