GENERALIZED STRATIGRAPHIC COLUMN NEAR RED LODGE, MONTANA
REGIONAL THICKNESS
EOCENE ABSAROKA VOLCANIC SUPERGROUP 8000' MAINLY ANDESITIC, BASALTIC, AND DACITIC VOLCANICLASTICS (INCLUDING BRECCIAS, CONGLOMERATES, SANDSTONES, SILTSTONES, AND TUFS) INTERBEDDED WITH LAVA FLOWS AND VENT BRECCIAS; PETRIFIED TREES AND LEAF FOSSILS COMMON.
WILLMUD FM 2300' VARIEGATED UNITS OF GRAY, RED AND PURPLE MUDSTONES WITH OCCASIONAL THIN SANDSTONES. MAMMALIAN BONES COMMON. PLANT REMAINS PRESENT IN TABULAR AND LENTICULAR CARBONACEOUS SHALES.
PALEOCENE FORT UNION FM 3,000'-12,000' INTERBEDDED YELLOWISH, LENTICULAR SANDSTONES AND YELLOW-GRAY MUDSTONES; LACUSTRINE BELFRY MEMBER NEAR MIDDLE; COAL-BEARING MEMBER IN UPPER PART; SYNTECTONIC CONGLOMERATES AND BRECCIAS AT TOP OF SECTION ALONG MOUNTAIN FRONT; FOSSIL LEAVES COMMON, BONES RARE.
CRETACEOUS LANCE FM 750-1000' THICK AND LATERALLY EXTENSIVE YELLOW SANDSTONES INTERBEDDED WITH GRAY, GRAY MUDSTONES. OCCASIONAL DINOSAUR BONES.
MEETETESE FM 1200' BANDED GRAY MUDSTONES WITH INTERBEDDED SANDSTONES AND OCCASIONAL THIN LIGNITES. MUDSTONES ARE ROOTED AND CONTAIN PLANTS, FRESHWATER MOLLUSCS, AND DINOSAUR BONES. A SANDSTONE UNIT NEAR MIDDLE CONTAINS A MARINE TRACE FOSSIL ASSEMBLAGE.
JUDITH RIVER FM 500-900' LIGHT-COLORED YELLOWISH SANDSTONES INTERBEDDED WITH YELLOWISH-GRAY SANDY SHALES AND SILTSTONES; FEW BEDS OF DARK GRAY CARBONACEOUS SHALES; OCCASIONAL THIN COAL BEDS; COMMON DINOSAUR BONES AND OCCASIONAL FOSSIL PLANTS
CLAGGETT FM 120-500' BROWN TO GRAY SHALE WITH STRINGER SANDS NEAR TOP, GRADING UPWARD INTO MASSIVE RUSTY SANDSTONE. COMMONLY DARK NEAR BOTTOM AND LIGHTER NEAR TOP - PARKMAN MEMBER: THICK BENTONITE BELOW SHALE, NEAR BASE OF FORMATION,
EAGLE FM 200-550' INTERBEDDED RIDGE-FORMING SANDSTONES WITH INTERBEDDED SHALES; COAL BETWEEN LOWER SANDS; SANDSTONES NOT CONTINUOUS: MASSIVE, RUSTY, PITTED SANDSTONE AT BASE - VIRGELLE MEMBER.
TELEGRAPH CREEK FM 150-400' GREENISH-GRAY SHALE, SOME GYPSUM; SALT AND PEPPER SANDSTONE FORMS SHOULDER-LIKE MOUND IN UPPER PART: TWO PROMINENT RUSTY SANDSTONE RIDGE-FORMERS AT BASE. VERY FOSSILIFEROUS - ELK BASIN SANDSTONE MEMBER.
CARLILE - NIobrARA SH 1000-1600' CODY SH VERY THICK SHALE, GRAY ON FRESH SURFACE, WEATHERS ALMOST WHITE; VERY LARGE CONCRETIONS NEAR TOP AS WELL AS LOWER IN FORMATION: LARGE AMMONITES FOUND IN CERTAIN LOCALITIES - EQUAL TO PART OR ALL OF 'CODY SHALE.
FRONTIER FM 300-600' MASSIVE GRAY, RESISTANT SANDSTONES INTERCALATED WITH THINLY-BEDDED BROWN SANDY SHALE AND BLACK SHALE: LARGE THREE-FOOT CONCRETIONS NEAR TOP: FEW BEDS OF CHERT-PEBBLE CONGLOMERATE.
POWRY SH 350-500' BROWNIISH-GRAY, HARD, RESISTANT SANDSTONE AND SOME BLACK SHALE: NUMEROUS FISH SCALES UP TO ONE AND ONE-HALF INCHES IN LOWER 250 FEET; SIDEITE CONCRETIONS COMMON 150 TO 300 FEET FROM TOP IN BLACK SHALES.
THERMOPOLIS SH 500-600' DARK GRAY TO BLACK, THINLY-BEDDED, SOFT SHALES. NON-RESISTANT, INTERBEDDED WITH SEVERAL BENTONITE BEDS: SANDSTONE UNIT BETWEEN TWO AND THREE HUNDRED FEET ABOVE BASE.
JURASSIC CLOVERLY FM 150-350' BASAL BLACK CHERT CONGLOMERATES OR PEBBLY, YELLOWISH SANDSTONES: REDDISH SHALES INTERCALATED WITH ANDESITIC AGGLOMERATES AND YELLOW SANDSTONE IN MIDDLE PORTION; GRAY-BROWN SANDSTONE AND SANDY SHALES TOWARD TOP.
MORRISON FM 200-350' VARIEGATED REDDISH, GREENISH, PURPLISH, AND GRAY CLAYS AND SHALES INTERBEDDED WITH LIGHT YELLOWISH-GRAY SANDSTONES: RARE OCCURRENCES OF DINOSAUR BONES AND GASTROLITHS.
SUNDANCE FM 350-600' BASAL GREEN-BROWN & RED CLAY; SHALES: THIN BEDS OF GYPSUM AND LS; MIDDLE GRAY CLAYS & SANDSTONE WEATHERING GREEN-BROWN: UPPER RESISTANT SS, GLAUCONITIC: COMMON BELEMNITES, CRINOID STEMS, AND THE MOLLUSCS, CRYPHEA
GYPSUM SPRINGS FM 40-200' THIN-BEDDED GRAY LIMESTONES AND REDDISH SHALES: THINLY TO MASSIVELY BEDDED GYPSUM TOWARD TOP.
TRIASS. PERM CHUGWATER FM 180-600' BRIGHT TO DARK RED SHALES, SILTSTONES, AND SANDSTONES: MUCH GYPSUM SCATTERED IN BASAL TWENTY FEET.
PARK CITY FM 10-70' POROUS, THIN-BEDDED, GRAY LIMESTONES: FEW DOLOMITE BEDS AND THIN CALCAREOUS SANDSTONES ("PHOSPHORIA FM")
MISSISSIPPIAN-PELM TENSLEEP SS 40-280' GRAY TO TAN, MASSIVE, CROSS-BEDDED, MEDIUM TO COARSE SANDSTONES: RESISTANT TO EROSION; UNFOSSILIFEROUS.
AMSDEN FM 80-140' RED SHALES AND SILTSTONES WITH INTERCALATED GRAY LIMESTONE AND DOLOMITE: LOCALLY GRAY, CHERTY SANDSTONE.
CAMBRIAN MADISON LS 700-900' CHIEFLY MASSIVE, LIGHT GRAY TO TAN LIMESTONES, COARSELY CRYSTALLINE TO FINE-GRAINED: SOME DOLOMITE AND LOCAL CHERTY ZONES; A FEW THINLY-BEDDED LIMESTONES; A VARIETY OF MARINE INVERTEBRATE FOSSILS FAIRLY COMMON.
DEVONIAN THREE FORKS FM 70-140' PLATY, LIGHT GRAY AND YELLOW TO BROWN AND REDDISH LIMESTONE AND DOLOMITE: THICKER CALCAREOUS SANDSTONE AT BASE.
JEFFERSON LS 220-375' ALTERNATING THINLY-TO-THICKLY BEDDED LIGHT GRAY TO BROWN LIMESTONES AND DOLOMITES WITH PETID ODOR; FEW FINE BRECCIA BEDS: CALCAREOUS SANDSTONE AT BASE: BRACHIOPODS (AIRYBAS, ETC.) FAIRLY COMMON.
ORD. BEARTOOTH BUTTE FM 0-150' LOCAL LENSES OF THINLY-BEDDED RED AND BUFF CALCAREOUS SHALES AND THICKER BEDS OF YELLOWISH-WEATHERING, GRAY LIMESTONE AND INTRAFORMATIONAL LIMESTONE CONGLOMERATE: VERY COARSE BASAL CONGLOMERATE; FOSSIL FISHES AND PLANTS.
BIGHORN DOLOMITE 150-400' YELLOWISH-GRAY SANDY DOLOMITE, TEN FEET, OVERLAIN BY MASSIVE, CLIFF-FORMING BUFF, ROUGH WEATHERING DOLOMITE MOTTLED WITH GRAY CRYSTALS; THEN LESS RESISTANT, THIN-BEDDED. FINE-GRAINED LIMESTONE WITH RESISTANT DOLOMITE IN MIDDLE, SIXTY FEET THIS UNIT: TOP EIGHTY FEET SAME MASSIVE, MOTTLED DOLOMITE NEAR BOTTOM: FOSSILS RARE.
SNOWY RANGE FM 250-300' INTERCALATED GREENISH-GRAY SHALES AND INTRAFORMATIONAL CONGLOMERATES: LATTER CONTAINS DISTINCT SUB-ANGULAR, FLAT, GRAY PEBBLES; UPPER FORTY TO FIFTY FEET YELLOW TO GREENISH SHALE, GRAY TO BUFF DOLOMITE AND INTRAFORMATIONAL CONGLOMERATE (= GROVE CREEK MEMBER); PEbbles WELL-ROUNDED, GRAY WITH GREEN COATING: STAR-SHAPED FOSSILS IN MATRIX.
CAMBRIAN MAURICE FM 90-150' CLIFF-FORMING, THICKLY BEDDED, CRYSTALLINE LIMESTONE, LIGHT GRAY TO BUFF WITH SOME MOTTLING; OCCASIONALLY OOLITIC: TRILLOBITE REMAINS COMMON IN COQUINA ABOUT THIRTY FEET ABOVE BASE AND IN TOPMOST BED.
PARK SH 350-475' GREENISH TO PURPLE SHALE INTERBEDDED WITH ONE INCH BEDS AND LENSES OF GRAY LIMESTONE; TOP FIFTY FEET CONTAINS DISTINCTIVE EDGWISE CONGLOMERATES WITH CLASTS AT ALL ANGLES TO BEDDING.
MEAGHER LS 40-100' THIN-BEDDED GRAY LIMESTONE, USUALLY IRREGULARLY WAVY-BEDDED: MIDDLE MEMBER, IF PRESENT, MAINLY SOFT, GREEN SHALES.
WOLSEY SH 50-200' GREEN, GRAY, PURPLE, PAPERY SHALES GRADING UP TO GREEN, BROWN, SANDY SHALES & SILTSTONES; TRILLOBITES FAIRLY COMMON.
PRE-C FLATHEAD SS 0-60' LIGHT TAN TO REDDISH TO WHITE, MEDIUM SANDSTONE, QUARTZITE, LOCALLY CGS: SANDSTONE COARSE & ARKOSIC TOWARD BASE.
"BASEMENT" COMPLEX OF GRANITIC GNEISSES AND DARK SCHISTES, INTRUDED BY MAFIC DIKES, ETC.
COMPILED BY KELLING DOF H. S. KAUFMAN A. JOHNSON NOTE: RELATIVE THICKNESSES PROPORTIONAL (APPROXIMATELY TO SCALE) WITHIN EACH ERA BUT NOT BETWEEN ERAS. TOTAL PALEOZOIC ABOUT 3000'; TOTAL MESOZOIC ABOUT 8500'; TOTAL CENOZOIC ABOUT 13,000' FEET. 1989