Unit is named the Upsal Hogback Bed of the Carson Desert Formation. Is exposed in the Carson Desert, Lake Lahontan area, NV. Consists of brown, potassium-poor, basaltic tephra containing blocky shards. Eruption may have continued over a considerable time and there may be several beds of similar composition. Some of the tephra included in the Upsal Hogback may be from the younger Soda Lake Bed (new) of the Carson Desert because the two vents may have shared the same magma source and therefore early Soda Lake tephra might resemble late Upsal Hogback tephra. Overlies the lower member of the Sehoo Formation and the Wono and Leter Ranch Beds of the Pyramid Lake Member (all new) of the Mount Mazama Formation. Age is Pleistocene, 35 to 11.5 ka. (B1565)

Source: GNU records (USGS DDS-6; Menlo GNULEX).