Sailor Canyon Formation and associated units
Sailor Canyon Formation and associated units
Middle Jurassic to Late Triassic
In the type area northwest of Lake Tahoe, the Sailor Canyon Formation is chiefly black slate, volcaniclastic sandstone, tuff, siltstone, and minor limestone. Fossils here range from late Sinemurian ammonites near the base to early Bajocian ammonites near the top (Clark and others, 1962; Imlay, 1968; Harwood, 1992). In the Mount Tallac roof pendant, it is made up of marine sedimentary rock; tuffaceous sandstone overlying feldspathic sandstone overlying quartzose sandstone, with a basal unit of laminated sandstone, siltstone, and calcarenite. The basal unit here contains probable late Pleinsbachian ammonites (Fisher, 1989). This part of the unit extends southeast to the roof pendants near Hope Valley, which are made up of metamorphosed graywacke, calcareous sandstone and siltstone, limestone, and andesite flows and tuffs (Armin and others, 1984).
The Sailor Canyon Formation is underlain in the type area northwest of Lake Tahoe by a relatively thin unit of conglomerate overlain by limestone and limestone breccia overlain by volcaniclastic sandstone, tuff, and andesite lapilli tuff, which pinch out to the north, and are in turn overlain by sandstone and conglomerate (the Big Valley sequence of Christe and others, 2018). The basal conglomerate lies in angular unconformity on the underlying Paleozoic rocks, and clasts in the basal conglomerate reflect local detritus derived from them. The limestone has yielded late Carnian through Norian conodonts (Harwood, 1983), whereas the uppermost sandstone unit has yielded a detrital zircon MDA of ~187 Ma (Christe and others, 2018). This entire sequence pinches out to the north, and the Sailor Canyon Formation rests directly on Paleozoic rocks north of the Emigrant Gap intrusive complex.
East of Talbot fault, correlative units in the Lake Tahoe sequence (Harwood, 1992) are the Early Jurassic Blackwood Creek Formation and the gradationally overlying Ellis Peak Formation, but these are too small to depict on this compilation and are included in the Tuttle Lake Formation and upper Lake Tahoe sequence (unit NSTT).
The formally accepted age of this unit is Early and Middle Jurassic, but we extend the age range to Late Triassic based on ages of conglomerate and limestone units described above.