Montana Group

Geology

Formations: unnamed (2), Bearpaw Shale (38), Claggett (1), Eagle Sandstone (4), Fox Hills (25), Hell Creek (98), Horsethief (1), Judith River (89), Lance (2), Lewis Shale (1), Pierre Shale (129), Two Medicine (73), Virgelle Sandstone (1)

Lithologies: not reported (162), "siliciclastic" (9), claystone (17), mudstone (41), "shale" (113), siltstone (16), sandstone (107), conglomerate (6), marl (1), lime mudstone (1), "limestone" (17), "carbonate" (3), amber (1), coal (2), lignite (1), ironstone (1), ash (2)

Paleoenvironments: marine indet. (137), terrestrial indet. (177), offshore indet. (1), marginal marine indet. (12), coastal indet. (8), estuary/bay (1), paralic indet. (1), delta plain (2), deltaic indet. (4), offshore (26), basinal (siliciclastic) (6), deep-water indet. (14), fluvial indet. (10), channel lag (7), coarse channel fill (7), fine channel fill (6), "channel" (8), "floodplain" (10), crevasse splay (11), levee (1), mire/swamp (2), fluvial-lacustrine indet. (1), fluvial-deltaic indet. (1), lacustrine - large (1), lacustrine - small (4), pond (3), lacustrine indet. (3)

Age range: base of the Campanian to the top of the Late/Upper Maastrichtian or 83.60000 to 66.00000 Ma
Collections

Time interval Ma Country or state Original ID and collection number
Late/Upper Cretaceous100.5 - 66.0USA (Wyoming) (203423)
Late/Upper Santonian85.8 - 83.5USA (Montana) (100168)
Late/Upper Santonian - Early/Lower Campanian85.8 - 70.6USA (Montana) (133330)
Campanian83.6 - 72.1USA (Wyoming) (1619 105717)
Campanian83.6 - 72.1USA (Kansas) (71830 71831 71832 71833 71834 71835 71836)
Campanian83.6 - 72.1Canada (Manitoba) (36754)
Campanian83.6 - 72.1USA (South Dakota) (28367 52084 107673 107779 107781 142359 142414)
Campanian83.6 - 72.1USA (Montana) (52873 57142 187419 64789 87725 107426 167793)
Campanian83.6 - 72.1USA (Colorado) (217722)
Campanian - Maastrichtian83.6 - 66.0USA (Colorado) (123398)
Early/Lower Campanian83.5 - 70.6USA (Wyoming) (1737 77348 94650 117858 117859)
Early/Lower Campanian83.5 - 70.6USA (South Dakota) (35333 39388 94635 94636 94637 94638 94639 94641 94643 94644 94645 94646 94647 94648 213531)
Early/Lower Campanian83.5 - 70.6USA (Montana) (33435 100163 178886 187420)
Early/Lower Campanian83.5 - 70.6Canada (Manitoba) (23307 23321 23323 23337 23338 23339 23366 36446 96685 193920)
Early/Lower Campanian - Middle Campanian83.5 - 70.6Canada (Manitoba) (78226 127632 193928)
Early/Lower Campanian - Middle Campanian83.5 - 70.6USA (Kansas) (71829 77321 114240)
Early/Lower Campanian - Middle Campanian83.5 - 70.6USA (Wyoming) (1743 1742 77312)
Early/Lower Campanian - Middle Campanian83.5 - 70.6USA (South Dakota) (77316 101100 102092 107642 107676 117861)
Early/Lower Campanian - Middle Campanian83.5 - 70.6USA (Nebraska) (116621)
Late/Upper Campanian83.5 - 70.6USA (Colorado) (88453 90153 90154 90155 90156 90158 90159 178348 178349 178350 178351 178352 178353 178354 178527 178529 178531 178532 178533 178539 178540 178541 178542 216750)
Late/Upper Campanian83.5 - 70.6Canada (Alberta) (53051)
Late/Upper Campanian83.5 - 70.6USA (Montana) (13282 14447 22652 22689 22690 22692 22693 22694 25658 26766 26767 36934 45680 45681 45682 50083 52435 53042 53043 53044 53045 53046 53047 53048 53052 53996 55274 55324 55386 59373 61843 62541 62723 68045 69931 70051 90189 102069 107428 107718 111375 138980 142498 156538 175762 177980 178029 178316 178317 178318 178319 178320 178321 178323 178324 178325 178326 178327 178328 178329 178330 178331 178332 178333 178334 178335 178336 178337 178338 178339 178340 178341 184945 190394 196407 219740 220335 230098 230102 231025 232277 236765)
Late/Upper Campanian83.5 - 70.6USA (South Dakota) (78181 107704 107780 123581 123582 212982 212993 212994)
Late/Upper Campanian83.5 - 70.6USA (North Dakota) (179297)
Late/Upper Campanian - Middle Campanian83.5 - 70.6USA (Montana) (142496 150896 150977)
Middle Campanian83.5 - 70.6USA (South Dakota) (85236)
Middle Campanian83.5 - 70.6Canada (Manitoba) (84462 84463 84464 84465 84466)
Middle Campanian83.5 - 70.6USA (Montana) (13281 14437 14453 14482 22653 22691 26775 26779 36608 46121 47101 53055 53056 53057 53058 69152 69281 73891 100851 120363 142497 167804 216964 227264 228490 229345 236763 236764)
Middle Campanian83.5 - 70.6USA (Wyoming) (117860)
Middle Campanian83.5 - 70.6USA (Kansas) (25692 49039 106060 132509)
Middle Campanian - Late/Upper Campanian83.5 - 70.6USA (Montana) (14432 14434 14435 14445 14446 14448 14449 14450 14457 14459 14460 14461 14462 14468 14470 14483 14490 14491 14492 23549 23551 32404 34016 46122 46123 46124 48620 49001 50825 50826 50827 50828 50829 50830 50906 50907 50909 51682 51683 53999 54000 58156 59217 60518 61452 62539 62540 64643 64785 64788 69213 69624 122333 128455 128560 138573 140916 142328 142495 142499 142506 142510 142511 142512 167800 167801 167802 177027 177030 177498 194654 206062 219741 219742 219743 222122 223339 231393)
Middle Campanian - Late/Upper Campanian83.5 - 70.6USA (South Dakota) (142509)
Middle Campanian - Late/Upper Campanian83.5 - 70.6Canada (Saskatchewan) (14493 14494 75030)
Late/Upper Campanian - Early/Lower Maastrichtian83.5 - 66.0USA (Colorado) (90157 90160)
Late/Upper Campanian - Early/Lower Maastrichtian83.5 - 66.0USA (South Dakota) (134955)
Maastrichtian72.1 - 66.0USA (South Dakota) (90228 90229 90230 90926 124207 135805 225317 225924 229369 229573 233264)
Maastrichtian72.1 - 66.0USA (Wyoming) (1576 87746 176023 225318 225319)
Maastrichtian72.1 - 66.0USA (North Dakota) (231457 231458 231461 231462 231463 231466 231467 231469)
Maastrichtian72.1 - 66.0Canada (Alberta) (72265)
Maastrichtian72.1 - 66.0USA (Montana) (87747 237407)
Early/Lower Maastrichtian70.6 - 66.0USA (South Dakota) (88513 88514 178587)
Early/Lower Maastrichtian70.6 - 66.0USA (Wyoming) (1575 1577 78177 191855)
Early/Lower Maastrichtian - Late/Upper Maastrichtian70.6 - 66.0USA (Kansas) (71837)
Early/Lower Maastrichtian - Late/Upper Maastrichtian70.6 - 66.0USA (Colorado) (71838)
Lancian70.6 - 66.0USA (North Dakota) (14610 14620 14621 53234 137706 137728 183291)
Lancian70.6 - 66.0USA (Montana) (14506 14507 14508 14509 14515 14534 14535 14536 14548 14549 14574 14582 14615 14653 14654 144500 144502 192245 223935)
Lancian70.6 - 66.0USA (South Dakota) (14537 14571 14604 14612 223934)
Late/Upper Maastrichtian70.6 - 66.0USA (Montana) (45879 217183 52903 52904 59374 72143 99441 123099 123683 157187 173842 206797 206798 221004 221005 221006 221007 224286 225035 238642)
Late/Upper Maastrichtian70.6 - 66.0USA (South Dakota) (24790 45388 45389 45390 47034 88512 97798 156591 157189 174241 179294 179296 206554 216603 221943 224370 224483 224484 224486 224487 224488 224489 224490 224491 224492)
Late/Upper Maastrichtian70.6 - 66.0USA (North Dakota) (24851 33437 45123 57919 118381 122903 122904 127733 137718 137720 179279 179280 179281 179282 179283 179284 179285 179286 179287 179288 179289 179292 179293 179295 191374 231459 231464 231465)
Late/Upper Maastrichtian70.6 - 66.0USA (Wyoming) (46117 175972)