Abstract The Triassic Fundy rift basin in Nova Scotia is a large (>70 km wide) half-graben filled with alluvial, lacustrine and aeolian deposits. A major lithospheric lineament, the Cobequid–Chedabucto Fault Zone (CCFZ), which forms the tip of the Newfoundland–Gibraltar Fault Zone, occurs within the Fundy Basin. The timing of early movement on this important fault zone is poorly constrained. We present data from the alluvial and aeolian units that crop out adjacent to the CCFZ in the Minas sub-basin to determine the initiation of fault movement. We use the onset of alluvial fan deposition to infer when the fault became sufficiently active to create the intrabasinal topography and document the influence of fault activity on the intrabasinal drainage. The occurrence and preservation of aeolian deposits immediately adjacent to the CCFZ and concomitant with alluvial fan development suggests a wind shadow effect associated with the fault-generated topography. The onset of alluvial fan deposition associated directly with the fault occurred during Norian times, following an earlier phase of sedimentation in the Fundy Basin, and records a potentially important phase of plate reorganization during early Atlantic rifting.

ABSTRACT Hydrovolcanic eruptions occur when rising magma violently fragments while mixing with shallow surface water or groundwater. These eruptions, among the most violent on Earth, generate hundreds to thousands of explosions throughout the course of an eruptive event. Each of these explosions ejects a mixture of juvenile and accidental clasts, gas, and water droplets. The solid materials either fall to the ground from tephra jets or collapse to form pyroclastic density currents (PDCs). The deposits of these eruptions build up rings of bedded tuff around the vent, recording both a wide variety of pyroclastic depositional mechanisms, and important changes in the eruptive style with time. This field trip will explore the deposits of basaltic, hydrovolcanic eruptions in the Fort Rock–Christmas Valley basin, the location of an intermittent, fluctuating, widespread Pleistocene lake (Fossil Lake). Basaltic volcanoes erupted in the center of the lake basin are characterized by Surtseyan eruptions (standing water), along the lake basin margins by maar eruptions (groundwater), and beyond the lake margin by scoria cones. The focus of the trip will be Fort Rock (Surtseyan) and the Table Rock Complex (large Surtseyan-tuff cone, large maar, and seven minor craters). This trip offers the opportunity to examine (1) settings under which explosive hydrovolcanic eruptions occur, (2) depositional characteristics that infer eruptive conditions, (3) a wide variety of pyroclastic deposits (i.e., fallout through air or a body of water, eruption-fed subaqueous sediment gravity current deposits, PDC deposits), and (4) mega-dunes (200 m wavelength dunes associated with large scale, dilute, PDCs from an energetic, mafic hydrovolcanic eruption).

Abstract This field trip covers sedimentological and paleontological research being conducted on the Jurassic Aztec Sandstone and Lower Cretaceous Willow Tank Formation in Valley of Fire State Park. Valley of Fire State Park is located in southern Nevada, just outside of the town of Overton. The Jurassic Aztec Sandstone is equivalent to the Navajo and Nugget Sandstones; these formations together record an aerially large erg complex along the western margin of North America during the time of deposition. Invertebrate and vertebrate ichnofossils are not uncommon in portions of these Jurassic formations. The Willow Tank Formation is composed of the deposits of both a braided and anastomosed fluvial system. This system drained off the paleohigh of the Sevier fold and thrust front to the west, during Early Cretaceous time. Recently a diverse vertebrate assemblage has been discovered from this formation. The fauna of the Willow Tank Formation are similar to other Early Cretaceous faunas from western North America. The vertebrate remains recovered include three taxa of fish, three to four taxa of turtle, crocodilian, iguanodontian, thyreophoran, dromaeosaur, tyrannosauroid, two theropod ootaxa, and a titanosauriform. In addition to the vertebrate elements, two fern morphotypes have been found. Through the course of this field trip participants will see extensive exposures of Aztec Sandstone, including vertebrate ichnofossils. Participants will also hike to vertebrate bearing-beds of the Willow Tank Formation.