Depositional environments of the Eagle Sandstone, north-central Montana-- an aid for hydrocarbon exploration (modified from a talk presented to the Rocky Mountain Section AAPG-SEPM Meeting, Billings, Montana, March 30, 1976)

1976 ◽  
Author(s):  
Dudley D. Rice
Keyword(s):  
Rocky Mountain ◽  
Depositional Environments ◽  
Hydrocarbon Exploration ◽  
North Central ◽  
Central Montana

Litho- and chronostratigraphic relationships of the Santonian–Campanian Milk River Formation in southern Alberta and Eagle Formation in Montana utilising stratigraphy, U–Pb geochronology, and palynology

2002 ◽  
Vol 39 (10) ◽  
pp. 1553-1577 ◽  
Author(s):  
Tobias HD Payenberg ◽  
Dennis R Braman ◽  
Donald W Davis ◽  
Andrew D Miall
Keyword(s):  
Late Cretaceous ◽  
Depositional Environments ◽  
North Central ◽  
Zircon Age ◽  
Southern Alberta ◽  
Central Montana ◽  
Milk River Formation ◽  
Eagle Formation ◽  
Provincial Park

U–Pb geochronology, palynology, and lithostratigraphy were employed on the Late Cretaceous rocks in southern Alberta and Montana to solve litho- and chronostratigraphic correlation problems. In the outcrop area around Writing-On-Stone Provincial Park, southern Alberta, the Milk River Formation has a Santonian to possibly very earliest Campanian age and was deposited between ~84.5 Ma and 83.5 Ma. In southern Montana, the Eagle Formation was deposited from ~83.5 Ma to 81.2 Ma, and contains different lithologies and depositional environments as opposed to southern Alberta. In north-central Montana, the Telegraph Creek Formation and Virgelle and Deadhorse Coulee members are equivalent in depositional environments and time to those of the Milk River Formation in southern Alberta. The upper Eagle member, however, has no time- or facies-equivalent rocks around Writing-On-Stone Provincial Park, but is time equivalent to the Alderson Member of the Lea Park Formation in southeastern Alberta. A hiatus of ~2.5 Ma is present between the top of the Milk River Formation in the outcrop area and the basal beds of the Pakowki Formation. The Pakowki transgression occurred at around 81.0 Ma based on a U–Pb zircon age of 80.7 ± 0.2 Ma from bentonite beds just above the bottom of the Pakowki Formation in southern Alberta. This age agrees with previous ages of 80.7 ± 0.6 Ma for the Ardmore Bentonite Beds and ~81.0 Ma for the Claggett transgression in southern Montana.

Dwarf Shrew (Sorex nanus) in North-Central Montana

1977 ◽  
Vol 58 (2) ◽  
pp. 248-250 ◽  
Author(s):  
L. S. Thompson
Keyword(s):  
North Central ◽  
Central Montana

Evidence for Picea pungens in north-central Montana and its significance

1978 ◽  
Vol 56 (9) ◽  
pp. 1118-1121 ◽  
Author(s):  
W. L. Strong
Keyword(s):  
Native Species ◽  
The State ◽  
Geographical Range ◽  
North Central ◽  
Picea Pungens ◽  
Central Montana

The analysis of Picea cone scales from the Sweetgrass Hills of Montana substantiates the existence of Picea pungens Engelm. in north-central Montana. These results extend the geographical range of P. pungens and identify a new native species within the state of Montana.

Isotaphonomy in concept and practice: an exploration of vertebrate microfossil bonebeds in the Upper Cretaceous (Campanian) Judith River Formation, north-central Montana

Paleobiology ◽  
2017 ◽  
Vol 43 (2) ◽  
pp. 248-273 ◽  
Author(s):  
Raymond R. Rogers ◽  
Matthew T. Carrano ◽  
Kristina A. Curry Rogers ◽  
Magaly Perez ◽  
Anik K. Regan
Keyword(s):  
Upper Cretaceous ◽  
Statistical Tests ◽  
Sampling Strategies ◽  
North Central ◽  
Wetland Ecosystems ◽  
Future Studies ◽  
Size And Shape ◽  
Definition Of ◽  
Central Montana ◽  
Judith River Formation

AbstractVertebrate microfossil bonebeds (VMBs)—localized concentrations of small resilient vertebrate hard parts—are commonly studied to recover otherwise rarely found small-bodied taxa, and to document relative taxonomic abundance and species richness in ancient vertebrate communities. Analyses of taphonomic comparability among VMBs have often found significant differences in size and shape distributions, and thus considered them to be non-isotaphonomic. Such outcomes of “strict” statistical tests of isotaphonomy suggest discouraging limits on the potential for broad, comparative paleoecological reconstruction using VMBs. Yet it is not surprising that sensitive statistical tests highlight variations among VMB sites, especially given the general lack of clarity with regard to the definition of “strict” isotaphonomic comparability. We rigorously sampled and compared six VMB localities representing two distinct paleoenvironments (channel and pond/lake) of the Upper Cretaceous Judith River Formation to evaluate biases related to sampling strategies and depositional context. Few defining distinctions in bioclast size and shape are evident in surface collections, and most site-to-site comparisons of sieved collections are indistinguishable (p≤0.003). These results provide a strong case for taphonomic equivalence among the majority of Judith River VMBs, and bode well for future studies of paleoecology, particularly in relation to investigations of faunal membership and community structure in Late Cretaceous wetland ecosystems. The taphonomic comparability of pond/lake and channel-hosted VMBs in the Judith River Formation is also consistent with a formative model that contends that channel-hosted VMBs were reworked from pre-existing pond/lake assemblages, and thus share taphonomic history.

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