Where: Alberta, Canada (49.0° N, 110.6° W: paleocoordinates 56.1° N, 75.4° W)
When: Baculites eliasi ammonoid zone, Unit 6 Member (Bearpaw Shale Formation), Campanian (83.6 - 72.1 Ma)
• The majority of the specimens described are
•from the Bearpaw Shale of eastern Montana
•which forms the upper part of the Montana
•Group and which was deposited in the Cre-
•taceous epeiric seaway (Gill & Cobban, 1966).
•The Bearpaw Shale is a westwardly thinning
•marine tongue of shale that interfingers with
•the subjacent Judith River Formation and the
•superjacent Fox Hills and Hell Creek Forma-
•tions (Text-fig. 1). The biostratigraphy of the
•Western Interior Cretaceous rocks has been-
•summarized by Gill & Cobban (1966). This
•ammonite zonation has been used by Gill &
•Cobban (1973) to map the position of strand
•lines for the time represented by the Bearpaw
•Shale.
•Most of the specimens were collected in the
•area around Ft. Peck Reservoir in northeast-
•ern Montana. The stratigraphy of the Bear-
•paw Shale in this area was investigated by
•Jensen & Varnes (1964). The lobster-bearing
•concretions were collected from "unit 6" of
•Jensen & Varnes (Text-fig. 3). This interval
•consists of 78 m (255 ft) of gray shale beds and
•contains gray weathering fossiliferous lime-
•stone concretions. The underlying interval (unit
•5) is bentonitic and, upon weathering, forms a
•hard surficial crust 0.3 m (1 ft) thick and con-
•tains abundant clay-ironstone concretions.
•Baculites associated with the lobsters were
•collected by Bishop at localities B-29 and
•B-30. They were submitted to W. A. Cobban
•of the U.S. Geological Survey who identified
•them (Cobban, personal commun. 1973) as
•Baculites eliasi (seven specimens from B-30)
•and Baculites eliasi or B. jensensi (one speci-
•men each from B-29). Both of these forms are
•latest Campanian in age (Gill & Cobban, 1966,
•p. A35) and have an estimated absolute age of
•71 my BP (Gill & Cobban, 1973, p. 4).
Environment/lithology: offshore; concretionary shale
•fossiliferous concretions was observed at sev-
•eral places. Locality B-29 occurs at an eleva-
•tion of 758 m (2,500 ft), high on a ridge west of
•Ft. Peck Reservoir. Specimens from the Pines
•Recreation Area B-22 occur above lake level
•at 663 m (2176 ft) and those at locality B-30 on
•the east side of the lake occur at lake level. A
•three point solution demonstrates that these
•three localities lie in a surface that very closely
•approximates the regional dip as shown by the
•structure contour map of Jensen & Varnes
•(1964). Although it could not be demonstrated
•conclusively that it is a single horizon, at least
•the horizon(s) is confined to the lower part of
•the upper unit (unit 6) of Jensen & Varnes
•(1964).
•At both localities the interval of small gray
•concretions was overlain by numerous larger
•concretions up to 1 m in diameter scattered
•through the shale. A few lobsters were found
•at each locality in the larger concretions.
Size class: macrofossils
Preservation: concretion
Primary reference: R. M. Feldmann, G. A. Bishop, and T. W. Kammer. 1977. Macrurous Decapods from the Bearpaw Shale (Cretaceous: Campanian) of Northeastern Montana. Journal of Paleontology 51(6):1161-1180 [M. Clapham/D. Sammanna]more details
Purpose of describing collection: taxonomic analysis
PaleoDB collection 235837: authorized by Matthew Clapham, entered by J Fearon on 09.08.2024
Creative Commons license: CC BY (attribution)
Taxonomic list