Tocito sandstone lentil of Mancos shale. On Chaco and San Juan Rivers near the Hogback, northwestern New Mexico, a notable bed of coarse brown cross-bedded sandstone, about 35 feet thick, occurs 735+/- feet above base of Mancos shale. It contains lenses of pebbles of chert and quartz as much as 0.5 inch diameter and resistant enough to make a cliff. It is known to petroleum geologists as Tocito sandstone, though sometimes also called by them Frontier sandstone. In this report it is called Tocito sandstone lentil of Mancos shale. Fossiliferous (INOCERAMUS UMBONATUS, OSTREA CONGESTA). Age is Late Cretaceous. Report includes columnar section.
Named from outcrops of the sandstone near Tocito Trading Post, San Juan Co., northwestern NM (San Juan basin). Also outcrops near Beautiful Mountain, about 25 mi southwest of type locality.

Source: US geologic names lexicon (USGS Bull. 896, p. 2157-2158); supplemental information from GNU records (USGS DDS-6; Denver GNULEX).

A three-fold division--1) even-bedded marine sandstone at base (correlated with the Gallup sandstone member of the Mesaverde formation), 2) thin irregular sandstone, shale, carbonaceous shale and occasional thin coal seams (correlated with the lower part of the Dilco coal member of the Mesaverde), and 3) coarse-grained, cross-bedded sandstone (probably equivalent to the stray sandstone of the southern San Juan basin and probably also equivalent to the lower part of the Dalton sandstone member of the Mesaverde in the Chuska Mountains)--have all been called Tocito sandstone lentil of the Mancos shale. Name Tocito abandoned.

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

Name Upper Cretaceous Tocito sandstone lentil of Mancos shale replaced by Gallup sandstone of Mesaverde group. [Tocito therefore "not used'; term "abandoned" not applied by authors.] Term Mesaverde raised to group rank throughout San Juan basin of southwest CO and northwest NM. Simplified geologic map. Diagrammatic cross section.

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

Reinstated as Tocito Sandstone Lentil of Upper Cretaceous Mancos Shale. Overlies middle unit and underlies El Vado Sandstone Member, both of Mancos. Name has had continued use since its abandonment (Pike, 1947) by some. Some have preferred to call the unit "transgressive Niobrara sandstones" of the San Juan basin. Tocito is composed of coarse- to fine-grained sandstone that occurs as lenses. Extends across the central San Juan basin.

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