Stratigraphy of Wyoming
Cenozoic Stratigraphy
Pleistocene-----------stream deposits----------16m-------rounded pebbles and cobbles.
Eocene---------------Aycross Fm.---------------200m------fluvial deposits of siltstones and mudstones.
-----------------------Willwood Fm.-------------700m-------variegated mudstones with multicolored paleosols. sublitharenite lenses.
Paleocene------------Fort Union Grp.----------330m-----sublitharenite, drab and carbonaceous shles, lignites and coal seams.
Mesozoic Stratigraphy
Cretaceous---------Lance Fm.---------------200m-------light-colored, drab shales. sandstones with cross- and convolute bedding.
----------------------Meeteetsa Fm.---------200m-------tan sandstone nobs, dark carbonaceous and drab shales with occasional coals. dinosaur fossils.
----------------------Mesa Verde Fm.-------250m-------grey shales and cliff-forming sublitharenites, interbedded shales, siltstones and sparse bentonite beds.
----------------------Cody Fm--------------700m-------dark grey marine shales.
----------------------Frontier Fm.---------150m-------grey shales, siltstones, limestones, and bentonite beds.
----------------------Mowry Fm.-----------150m--------sandy in lower part, but primarily grey to brown shales, interlaced bentonite beds.
----------------------Thermopolis Fm.-----175m--------litharenite with fish and shark teeth fossils, bentonitic black shales.
----------------------Cloverly Fm.--------100m--------rusty quartz arenites, basal conglomerates, fossil wood common.
Jurassic------------Morrison Fm.--------75m---------sparkly quartz arenites, multi-colored shales. kodachrome.
---------------------Sundance Fm.--------125m--------interbedded limestones and shales. contains oyster ridges locally.
Erosional Unconformity\/\/\/\/\/\/\/\
Triassic------------Gypsum Springs Fm.--0-20m-------bedded gypsum, red shales, some limestone.
---------------------Chugwater Fm.-------175m--------red mudstones and siltstones. gypsiforous, edgewise conglomerates, ripple marks, cross-beds, quartz arenites.
---------------------Dinwoody Fm.--------15m---------interbedded pastel shales with limestones and dolomite.
Paleozoic Stratigraphy
Permian-------------Park City Fm.---------20m-------vuggy limestones, bedded cherts and an to grey shales. brachiopods.
Erosional Unconformity/\/\/\/\/\/\/\/\
Pennsylvanian------Tensleep Fm.----------75m-------grey and tan massive quartz arenites, cross-bedding.
----------------------Amsden Fm.------------50m------red and purple shales, siltstones, grey limestones and dolomites.
Mississippian-------Madison Fm.----------300m-----massive grey to tan fine-grained limestones with vugs. crinoids, brachiopods, and orange coral.
Devonian------------Three Forks Fm.-------30m-----brown, grey and yellowish limestones and dolomites, with greyish-green shale and siltstone.
-----------------------Jefferson Limestone----90m-----brown limestones, some shales, and conglomerate at base.
-----------------------Beartooth Butte Fm.----0-25m---buff limy shales with limestone conglomerates at base. upper layers are thinly-bedded.
Erosional Unconformity/\/\/\/\/\/\/
Ordivician-----------Bighorn Fm.------------125m-----mottled grey, massive limestone. sugary in appearance.
Cambrian------------Gallatin Fm.----------130m------grey and green shales, flat-pebble conglomerates in limestone. limestones dominate.
-----------------------Gros Ventre Fm.-------230m-------grey and green shales with trilobites, interbedded limestone conglomerates.
-----------------------Flathead Fm.----------75m--------light-colored, grey quartz arenites, some mudstones at base.
Erosional Unconformity/\/\/\/\/\/\
PreCambrian Basement Complex
granitic gneisses and migmatites intruded by mafic
dikes.
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