The Bisoni-McKay area, a structurally isolated, fault-bounded horst, offset eastward at the south end of the Fish Creek Range, displays a geologic terrane that is previously unrecorded in Nevada, and perhaps elsewhere in North America. This unique terrane is an olistostrome that was shed eastward by listric faulting from the east side of the migrating Antler orogenic forebulge in Late Devonian (early Famennian, ca. 373 Ma) time. Stratigraphic identification of Devonian olistoliths and enclosing matrix that constitute the olistostrome, as well as overlying postemplacement units, is supported by correlation to formations in the main part of the Fish Creek Range and to the northwest in the northern Antelope Range. Precise zonal dating of map units and revised dating of Antler orogenic events are provided by 38 conodont collections recorded in the Devonian/Carboniferous (D/C) Conodont Database and by small collections of conodonts embedded in siltstone and mudstone. Our revision of regional geologic history uses Devonian conodont zones to measure “deep time” to circa millions of years before present. The upper Upper Devonian (Famennian) tongue of the Woodruff Formation was deposited directly on the olistostrome and is overlain by clastic Mississippian synorogenic deposits. These deposits were shed eastward from the evolving Antler highland and related Roberts Mountains allochthon into the Antler foredeep. We propose the following revised dates for important Devonian tectonic events in Nevada: initiation of Antler orogeny, ca. 385 Ma; downwarping of Pilot backbulge basin, ca. 382 Ma; initial uplift of the Antler highland, ca. 373 Ma; third, major pulse of highland uplift, ca. 364 Ma. A summation of regional geologic history indicates that the elapsed time from start of Antler orogeny to start of Roberts Mountains thrusting was ~30 m.y.

The King Ridge Road mélange is a unit of the Franciscan Complex, cropping out in an area of at least 50 km 2 around the town of Cazadero, coastal California. This unit is an olistostrome with a massive, unfoliated sandstone matrix, containing >232 large meta-igneous and chert blocks of greatly varying size, lithology, and metamorphic history within the study area. This sandstone matrix is litharenite or arkosic arenite and exhibits prograde prehnite-pumpellyite facies and retrograde zeolite facies metamorphism. It is devoid of megascopic textures except for rare simple bedding. No fossils have been found, and no Bouma units or other graded beds are present. Detrital zircon geochronology has established the maximum age of deposition of the sandstone matrix at 83 Ma, whereas apatite fission-track data indicate cooling of the olistostrome below 100 °C at ca. 35–38 Ma. The 232 exotic blocks sampled in the study area are dominantly low- to medium-grade greenstones and cherts, together with fewer high-grade blocks partly composed of blue amphibole and/or omphacitic pyroxene, and some amphibolites. Thus, many of the blocks have higher grade metamorphic assemblages than the matrix. All block types are well mixed together, so none greatly predominate anywhere. Blocks of oceanic-island-arc plutonic rocks, including granitoids and recemented breccias, are particularly distinctive for this mélange. One granitoid block has a zircon U-Pb age of 165 ± 1 Ma. The massive sandy matrix of the olistostrome formed by accumulation of hyperconcentrated sedimentary density flows (grain flows) sourced primarily from the Klamath-Sierra continental magmatic arc. Many of the blocks record a pre-mélange history of metamorphism and exhumation, followed by partial subduction and reburial with the matrix after 83 Ma. Cooling below 100 °C took place at 35–38 Ma, probably associated with partial exhumation of the unit, with subsequent removal of ~10 km of cover.