First published use as an unranked local dolomite in lower part of Minturn Formation. Original use was for a dolomite 600 ft below the Wearyman Dolomite Member in the Minturn area. Recognized in this report in outcrops near mouth of Gore Creek of the Eagle River, Eagle Co, CO in the Eagle basin. Is covered west of Gore Creek except for area near Avon. Pinches out to west or changes facies. Small bioherms present. Cross section. Overlies and underlies unnamed parts of Minturn. Pennsylvanian age.

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

Revised (mentioned on 2 pages) as Lionshead Member, a lower carbonate, one of eight, assigned to Minturn Formation in central CO, Eagle basin. [Intent to name, designation of a type, description of lithology and contacts, areal limits, thickness regionally not stated; a very casual introduction of a name.] Shown on a generalized column as a 10 to 30 ft thick unit of 3 dolomite beds separated by, underlain and overlain by clastic rocks about 1700 to 1800 ft above base [?] of Minturn. Minturn is Atokan and Desmoinesian, Middle Pennsylvanian age; [Lionshead is older than Robinson and could be either Atokan and/or Desmoinesian.]

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

Name was taken from a prominent feature known as the Lionshead in cliffs above town of Minturn south of the Gore River along U.S. Hwy 24, Eagle Co, CO in the Eagle basin. Consists entirely of dolomite. Is one of several bioherms in the Minturn Formation (of Des Moines age) that are concentrated in, but not limited to, an area in the transition zone between evaporite-bearing sediments in the central part of the Eagle basin and normal marine sediments in a marginal trough. The bioherms are localized upgrowths on algal biostromes; they developed in shallow marine water. Contemporaneous detrital sedimentation kept pace with algal growth that formed close to alluvial fans that prograded the Eagle basin. When influx of detritus was high, the biostromes were buried; when influx of detritus was low, algae flourished. Bioherms occur as isolated mounds rather than a continuous barrier.

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

First good published lithologic description of dolomite in measured type section of Minturn, sec 22, T5S, R80W, Eagle Co, CO, Eagle basin. Forms the top zone of clastic unit C of Minturn Formation. Consists in measured section of: dark gray (brown weathering), fine- to medium-grained, medium- to thick-bedded, slabby or flaggy dolomite 48 ft thick; is irregularly vuggy; contains poorly preserved fossils; calcite crystals in the vugs; conglomeratic grit butts against side of reef 20-35 ft above base; dolomite above the grit contains abundant quartz pebbles; overlies unnamed sandstone, siltstone, and grit of clastic unit C; upper surface of reef dolomite is irregular; underlies dark gray shale and interbedded dark gray limestone of clastic unit D of Minturn. Reef dolomite of Lionshead consists of discrete reefs strung at intervals along a thin, inconspicuous bed of dark dolomite. Abruptly pinches laterally from measured section to become 2 thin dolomite beds separated by several ft of grit. Figures Middle Pennsylvanian age.

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