GEOLEX

Summary of Citation: Eagle

Publication:
Weed, W.H., 1899, Description of the Fort Benton quadrangle
   [Montana]: U.S. Geological Survey Geologic Atlas of the United
   States, Fort Benton folio, no. 55, 7 p.

Usage in Publication:
Eagle formation*

Modifications:	Geologic Province:	Dominant Lithology:
Named	Sweetgrass arch	Sandstone

Summary:
Named for exposures along the Missouri River about the mouth of Eagle Creek, Choteau Co, MT on the Sweetgrass arch. No type locality designated. Contrasts with the dark shales of the underlying Colorado formation and the overlying Montana formation. Consists at base of thinly laminated sandstone stained brown by lignitic material that contains concretions and nodular masses of iron. Basal beds grade upward into white sandstone that forms cliffs or steep slopes 75 to 100 ft high. Upper part consists of shaly sandstone with lignite seams. Is 200 ft thick. Fossil plants, fresh water shells. Geologic map. Mapped in northeast corner of map area along the Missouri River.

Summary of Citation: Eagle

Publication:
Hatcher, J.B. and Stanton, T.W., 1903, The stratigraphic position
   of the Judith River beds and their correlation with the Belly
   River beds: Science, new series, v. 18, no. 150, p. 211-212

Usage in Publication:
Eagle formation*

Modifications:	Geologic Province:	Dominant Lithology:
Revised	Central Montana uplift

Summary:
Upper contact of Eagle revised in that it underlies the newly named Claggett formation in the area near the mouth of the Judith River in Fergus Co, MT on the Central Montana uplift. Overlies Colorado shales. Is 250 to 300 ft thick. Consists of coarse, light-colored sandstone with clay shale and lignite. Has a Fox Hills fauna.

Summary of Citation: Eagle

Publication:
Bowen, C.F., 1915, The stratigraphy of the Montana group, with
   special reference to the position and age of the Judith River
   formation in north-central Montana: U.S. Geological Survey
   Professional Paper, 90, p. 95-153

Usage in Publication:
Eagle sandstone*

Modifications:	Geologic Province:	Dominant Lithology:
Revised	Sweetgrass arch Central Montana uplift

Summary:
Revised in that the lower massive persistent sandstone member is named Virgelle sandstone member of Eagle sandstone of Montana group. Overlies Colorado shale. Underlies Claggett formation of Montana group. The Virgelle is 100 to 120 ft thick. The younger parts of the Eagle are designated (in sequence): middle member and upper member. In the southern part of study area, the Virgelle is gray to brown, massive, ledge-forming sandstone about 100 ft thick; the middle member is thin-bedded, shaly sandstone; and the upper member is thick-bedded, resistant sandstone that locally has large rusty-brown concretions. In the northern part of the study area, the middle member becomes carbonaceous and has thin streaks of coal. Eagle ranges from 200 ft thick in south to 300 ft thick on the Missouri River. Mapped (geologic map) between North Moccasin Mountains in Fergus Co south to Musselshell in Musselshell Co, MT on the Central Montana uplift. Virgelle named for locality on the Sweetgrass arch. Late Cretaceous age. Stratigraphic table.

Summary of Citation: Eagle

Publication:
Thom, W.T., Jr., 1923, Oil and gas prospects in and near the
   Crow Indian Reservation, Montana, IN Contributions to economic
   geology, 1922; Part 2, Mineral fuels: U.S. Geological Survey
   Bulletin, 736-B, p. B35-B53

Usage in Publication:
Eagle sandstone*

Modifications:	Geologic Province:	Dominant Lithology:
Revised	Central Montana uplift

Summary:
Revised in that Eagle sandstone overlies the newly named Telegraph Creek formation. Telegraph Creek occurs at the head of Telegraph Creek, T2S, Rs28 and 29E, Yellowstone Co, MT on the Central Montana uplift. Is of Late Cretaceous age.

Summary of Citation: Eagle

Publication:
Knechtel, M.M. and Patterson, S.H., 1956, Bentonite deposits in
   marine Cretaceous formations, Hardin district, Montana and
   Wyoming: U.S. Geological Survey Bulletin, 1023, 116 p.

Usage in Publication:
Eagle sandstone*

Modifications:	Geologic Province:	Dominant Lithology:
Not used

Summary:
Not used in report area of Big Horn Co, MT, northwest Powder River basin. Rocks assigned to Eagle by earlier workers are here assigned to unnamed sandy shale member in upper part of Cody shale. Reason for change in nomenclature is the predominance of shaly material in strata rather than thick, massive sandstones typical of Eagle that occur elsewhere in MT.

Summary of Citation: Eagle

Publication:
Fraser, G.D., Waldrop, H.A. and Hyden, H.J., 1969, Geology of
   the Gardiner area, Park County, Montana: U.S. Geological
   Survey Bulletin, 1277, 118 p.

Usage in Publication:
Eagle Sandstone*

Modifications:	Geologic Province:	Dominant Lithology:
Revised Overview	Montana folded belt province

Summary:
Upper contact revised in that Eagle Sandstone underlies the newly named Everts Formation. Study area is within southwest quarter of Gardiner 15-minute quad, Park Co, MT, Montana folded belt province. Overlies Telegraph Creek Formation. Geologic map, cross section. Can be divided into the lower bluff-forming Virgelle Sandstone Member at base and an upper coal member. Mapped in south-central part of quad. Measured sections. Virgelle is 163 ft thick and the coal member is 614 ft thick on west slope of Mount Everts (located south of Gardiner quad in Park Co, WY) where a complete section was measured. Appears massive but has many thin beds or laminae that are cross stratified. In report area, Virgelle is gray (stained yellow by limonite), fine- to medium-grained, angular, arkosic, calcareous sandstone that includes local coarse-grained lenses, and scattered granules or pebbles of chert. The coal member consists of interbedded calcareous, lenticular sandstone, carbonaceous shale, and coal. Pelecypod fossils (listed). Considered to be a regressive sandstone of early Late Cretaceous age.

Summary of Citation: Eagle

Publication:
Roberts, A.E., 1972, Cretaceous and early Tertiary depositional
   and tectonic history of the Livingston area, southwestern
   Montana, IN Geology of the Livingston area, southwestern
   Montana: U.S. Geological Survey Professional Paper, 526-C,
   p. C1-C120, (incl. geologic map, scale 1:62,500)

Usage in Publication:
Eagle Sandstone*

Modifications:	Geologic Province:	Dominant Lithology:
Overview Reference	Montana folded belt province Central Montana uplift Powder River basin	Sandstone Siltstone Coal

Summary:
Composed in Montana folded belt province, Central Montana uplift, Powder River basin, of lagoonal, estuarine, deltaic, swamp, and beach deposits that interfinger with marine near-shore and offshore deposits (east) and continental deposits (west). Ranges from 515 to 860 ft thick. Gradationally overlies Telegraph Creek Formation; gradationally overlain by Cokedale Formation, a conspicuous deposit containing andesitic detritus. Reference section measured north side, Miner Creek, NW1/4 sec 26, T2S, R8E, Park Co, where Virgelle Sandstone Member and upper part present. Virgelle 110 ft thick is composed of gray, coarse- to fine-grained, noncalcareous, thin- to medium-bedded to massive, cliff-forming sandstone that may be arkosic indurated to platy, poorly sorted and olive-gray thin-bedded siltstone. Upper part 645 ft thick includes: 1) sandstone that ranges from very fine grained, thin to thick bedded, calcareous, arkosic, poorly indurated to indurated, poorly sorted, slabby, platy; 2) light-gray to olive-gray siltstone that ranges from green-, olive- to dark-gray and gray-brown, very fine grained, tuffaceous, carbonaceous thin- to thick-bedded coal; and 3) dark-gray, microlitic, medium-bedded, very fine grained, andesitic, calcareous tuff. Composite section measured in NE1/4 sec 27, T2S, R9E (surface) and SW1/4 sec 11, T2S, R9E. Petrographic descriptions. Of early Campanian, Late Cretaceous age. Correlation chart. Geologic map.

Summary of Citation: Eagle

Publication:
Skipp, Betty and McGrew, L.W., 1977, The Maudlow and Sedan
   Formations of the Upper Cretaceous Livingston Group at the
   west edge of the Crazy Mountains basin, Montana, IN Contributions
   to stratigraphy: U.S. Geological Survey Bulletin, 1422-B, p.
   B1-B68

Usage in Publication:
Eagle Sandstone*

Modifications:	Geologic Province:	Dominant Lithology:
Revised	Montana folded belt province

Summary:
Upper contact revised. Underlies, in parts of Gallatin, Park, and Meagher Cos, MT in the Montana folded belt province, the newly named Sedan Formation of Livingston Group. Is of late Santonian and early Campanian age.

Summary of Citation: Eagle

Publication:
Tysdal, R.G., in press, Revision of Cretaceous Slim Sam Formation,
   Elkhorn Mountains area, Montana: U.S. Geological Survey
   Bulletin, __

Usage in Publication:
Eagle Sandstone*

Modifications:	Geologic Province:	Dominant Lithology:
Areal limits	Montana folded belt province

Summary:
Use of name extended into Elkhorn Mountains, Jefferson and Broadwater Cos, MT (Montana folded belt province). Eagle replaces uppermost part of lower part of Slim Sam Formation (revised) of Klepper and others (1957, USGS PP 292). Only lower part of Eagle is present and it occurs only locally; exposed 1 km southeast of top of Big Mountain and along road directly south of Weston Creek; best exposure is in a bulldozer trench west of Big Mountain. Correlates with Eagle in Livingston, MT, area. Conformably overlies Telegraph Creek Formation (which is also extended into Elkhorn Mountains); unconformably underlies Slim Sam. Correlation chart with fossil zones (fig. 3). Late Cretaceous (Santonian) age.