WebNov 18, 2024 · Consists of more or less sandy shale and siltstone with iron-stained concretions. Persistent thin beds of sandstone, locally conglomeratic and phosphatic and containing abundant shark teeth, in lower part. Marine fossils. Forms a minor scarp. A distinct faunal break and possible unconformity at base. WebDuring the late Cenomanian and early Turonian, the Greenhorn transgression floodedtheNorthAmericanforelandbasin to form a relatively shallow seaway (Fig. 1 ). This allowed for the deposi- tion of rhythmically bedded sequences, including organic-rich strata of the Greenhorn Formation and its equivalents.
Stratigraphic Framework of Lower and Upper …
WebGreenhorn Formation (Upper Cretaceous) at surface, covers 0.3 % of this area Gray shale, mudstone, marl, calcarenite, and shaly limestone grading upward into light-gray to tan, alternating marl and thin-bedded, fossiliferous limestone. Thickness up to 40 ft (12 m). Spearfish Formation (Triassic to Permian) at surface, covers 0.3 % of this area WebCretaceous rocks (Greenhorn Formation to Niobrara Formation). Table 1 lists the wells shown on the sections plus 22 additional wells used for greater mapping control. On the … knowledge consortium of gujarat ahmedabad
U.S. DEPARTMENT OF THE INTERIOR U.S.
WebThe lower Greenhorn Formation is characterized by dark-colored thinly laminated shale with rare biogenic and current-formed structures. It was deposited by pelagic settling in relatively quiet waters in anaerobic conditions. Rare storms reworked the sediments producing thin bioturbated intervals and thin limestone beds. WebNov 18, 2024 · Named as top formation of Lower Cretaceous series, top of Lower Cretaceous. Formerly called "formation No. 3" (Meek and Hayden, 1857). Type not designated. Named for Niobrara River, Knox Co, NE in Salina basin, where formation forms 90-100 ft cliffs near mouth along Missouri River. redbus tracking location