GeoNotes Cypress Hills and area
THE CYPRESS HILLS STRATIGRAPHIC SEQUENCE
the significance of the K-T boundary (65 Ma) and a major extinction event
The generalized stratigraphic sequence of the Cypress Hills (Fig. 1) consists of six formations beginning with the oldest; Eastend, Whitemud, Battle, Frenchman, Ravenscrag, and Cypress Hills resting on the marine Bearpaw shales that dominate the southern prairie region around the Cypress Hills. The shales were named after where they were first discovered near the Bearpaw Mountains in Montana.
The town of Eastend, Maple Creek, and Piapot, and the once hamlet of Ravenscrag and South Fork are built on the Bearpaw Formation. Dollard is situated on the Eastend Formation, and Shaunavon is built on the Eastend/Whitemud/Battle Formation.The warm shallow Bearpaw Sea (77-68 Ma) extended down the entire length of western North America from the Arctic Ocean to the Gulf of Mexico. This resulted in the deposition of the Bearpaw Formation. The formation is 250 m thick and was deposited during a relatively quiet geological time when mechanical erosion was low and rivers were carrying mainly finer suspended silts and clay minerals into the sea. There are also layers of volcanic ash deposits from the western Cordilleran orogeny that have been altered to the clay mineral bentonite. The shale and clay of the upper Bearpaw Formation in this area of the Cypress Hills contains more sand indicating an increase in mechanical weathering from geological activity in the west and southwest. The upper Bearpaw Formation also contains abundant gypsum (selenite) and clay iron concretions. Selenite, an evaporative mineral, can form crystals after a rain as the muddy clay dries.
Overall, the shallow sea life of the Bearpaw Formation consists of a variety of reptiles, vertebrate, and invertebrate marine fossils including gem-quality ammonites found in some areas, and a diversity of marine mollusks.
With the Bearpaw Sea starting to disappear after 69 Ma, and with continued periodic orogenic activity in the southwest, courser material was being intermittently deposited as sandstone. The Eastend Formation overlies the Bearpaw Formation and consists mainly of 125 m of sandstone, green-gray shale, and lignite coal seams. The lower portion of the Eastend Formation is made up of marine deposits containing marine mollusks while the upper part of the formation consists of non-marine sand, silts, and clays. The formation also has round and ovoid concretionary layers.
The non-marine deposits are an indication that the Bearpaw Sea has more or less disappeared from the area, and the low gradient rivers and streams are now depositing their load into a low-lying coastal plain containing swamps and marshes that are today thin lignite coal seams and the silts are the shale beds. Shallow lakes and ponds are also characteristic of a low-lying coastal plain geomorphology.
Lithic grain analysis of the non-marine Upper Eastend Formation revealed rapid mechanical weathering of newly extruded volcanic rocks. In contrast, the lithology of the overlying Whitemud Formation reveals a very quiet orogenic period resembling old worn down mountain ranges predominated by chemical weathering that altered the feldspar-rich volcanic tuffs, flows, and intrusive materials, and the feldspar-rich metamorphic rocks and clasts into kaolinitic clays at the source, and during and after the deposition of source materials. The lithic analysis also suggests the source material for both the Upper Eastend and Whitemud Formations came from Upper Cretaceous volcanic rocks, Precambrian rocks, Paleozoic metamorphic, and carbonate rocks all situated in Montana. These rocks are thought to come from the Late Cretaceous (81-74 Ma) igneous uplifts of the Elkhorn Mountains, 35 km SSE of Helena, MT predating the Eocene (55-50 Ma) Bearpaw Mountains and Sweetgrass Hills igneous intrusive uplifts.
The Whitemud Formation is 8 m thick and is characterized by white kaolinitic refractory clay that was commercially mined around Eastend and Ravenscrag in open pits during the early to late 20th century and is still mined today (quarry seen along Bench Road) by Plainsman Clays Ltd of Medicine Hat, AB. The clay is used in the manufacture of a wide range of products from pottery to sewer pipes. Refractory clay materials have the commercial advantage of being resistant to decomposition by heat, pressure, or chemical attack, and they retain their strength and form at high temperatures. The Whitemud Formation also contains brown fissile carbonaceous shales, siltstones, and thin beds of lignite coal. Plant fossils in the carbonaceous shales consist of aquatic plants such as water lilies, and trees and shrubs related to figs, hickories, and redwoods. Microfossils of spores and seed cuticles are also found. Indirect evidence of vertebrate fossils are scattered coprolites (fossilized feces) ranging in size from 2-23 cm representing fish feces, terrestrial reptiles, and fossilized unexpelled intestinal remains. The coprolites are well preserved as siderite (iron carbonate mineral) and iron hydroxides.
The Whitemud sediments are non-marine deposits on a floodplain overlain by the marine Battle Formation. It appears the Bearpaw Sea hadn’t completely left the area and periodically transgressed onto the low-lying marshlands depositing the 10 m thick distinctive mauve grey to purplish-brown mudstone or shale of the Battle Formation. The shale contains volcanic ash that has been altered to bentonite and montmorillonitic clay that forms a popcorn-like crust upon weathering.
The Battle Formation is thought to be marine because it contains foraminifera, single-cell shelled marine organisms. The formation is poorly fossilized containing spores, bone fragments, algal remains, and carbonized wood. After the regression of the Bearpaw Sea, there was a period of erosion, and the missing stratigraphy of the Battle Formation created an unconformity. The erosion ended with the deposition of the Frenchman Formation.
The Frenchman Formation is an olive green to brown 75 m thick alluvial floodplain deposit (Fig. 2) consisting of two non-marine facies of sand and clay that look similar to the Eastend Formation suggesting a return to an alluvial floodplain environment. The source rocks for the Frenchman Formation are thought to have come from fast mechanical weathering of Late Cretaceous volcanic rocks in SW Montana that were extruded before or during the deposition of the Frenchman Formation. These same rocks are also thought to be the source of the overlying Ravenscrag Formation. The boundary between the two formations created the well-known, and somewhat mysterious Cretaceous-Tertiary (K-T), known today as the Cretaceous-Paleogene (K-Pg), a boundary which in this area has preserved a continuous sequence of time before, during, and after the controversial mass extinction event.
Figure 2: Example of an alluvial floodplain deposit with braided stream channels 66 Ma. The mountainous area represents the north-central Montana uplifts. Image: University of Notre Dame.Fossilized plant remains are common in the Frenchman Formation, but remain mostly unidentified. Fauna of the Frenchman are crocodiles, lizards, snakes, turtles, champsosaurs, a few birds, and 14 dinosaur species. Champsosaurs fossil discoveries continue with the newest find made in August of 2020 near Climax, SK just above the K-T boundary. The Triceratops (65 Ma) account for 70% of the dinosaur fossil material in the formation. In recent years the Frenchman Formation has become world-famous with the 1991 discovery of a significant 65.5-65 Ma megafauna, Tyrannosaurus rex, or T. rex (Scotty) at Chambery Coulee, 27 km SE of Eastend, SK along the Frenchman River valley near Hwy 37.
Scotty, possibly the largest T.rex uncovered so far, was found 28.3 m below the iridium-enriched K-T boundary buried in the sand of a once gently meandering river channel point sand bar. The disarticulated skeleton is 75% complete, a rarity for T. rex skeletons. The cause of death is unknown, and the reptile died at or near the burial site. There is degradation on the bones indicating extensive aerial exposure before the gradual final burial.
Scotty’s skeletal discovery was associated with other bones and plants, another rarity, revealing the paleoenvironment at the time of burial. Embedded with the skeleton are a few fossils of ferns, gymnosperms, and angiosperms along with fish scales, and shells of gastropods and clams.
The T. rexes roamed in a broad valley with abundant deciduous flora. Since Saskatchewan was farther north 65 Ma ago than today, with reduced daylight, the vegetation entered into seasonal dormancy dropping its leaves in fall colour style. This left the herbivorous with a shortage of food, and in turn, left the T. rexes also without food. There is some speculation the T. rexes followed the migrating herbivores to new food sources. The regional climate was subtropical-warm temperate without winter or frost but had a seasonal drought. A regional study showed that the stratigraphy and biodiversity were maintained by local environmental conditions of less than 200 km. The annual mean temperature was 12 C with annual precipitation of 1120 mm. Compared with today’s annual mean temperature of 2 C and 380 mm of average annual precipitation.
The Frenchman Formation underlies the Ravenscrag Formation which is a 70 m thick non-marine alluvial floodplain deposit interbedded with sands, silts, and clays with an eastward thickening of sediment. Found throughout the Ravenscrag Formation are abundant well-preserved plant remains, coal seams, and scattered carbonaceous material. Megaflora fossils indicate marked seasonality in a subtropical-warm temperate environment. Channeling, scouring, and filling are present. Also within the formation are several cycles similar to the Whitemud Formation indicating a quieter geological time where chemical weathering predominated over mechanical weathering at the source. Within the Ravenscrag Formation is the Willowbunch Member which is also similar to the Whitemud Formation consisting of fine-grained sand, silts, and clays.
An interesting feature of the Ravenscrag Formation and other exposed coal-bearing formations is the rusty orange colour in the baked clay near coal seams that have caught fire during lightning strikes. On rare occasions, coal seams were intentionally set on fire by individuals.
The Ravenscrag Formation has economically low sulfur coal used to fuel Saskatchewan’s electric power stations, and the clays are used to make a variety of brick products. Coal mining is done in eastern Saskatchewan near Estevan close to the electric power plants. According to local accounts, small-scale limited lignite coal mining has occurred along the Frenchman River valley and South Fork, SK for personal use; however, there were and are no major commercial coal mining operations in the area. The first commercial coal mining operation began in SE SK near Roche PercĂ©e in 1880.
The Ravenscrag Formation was exposed to erosion creating an unconformity for some time before the Eocene orogenic phase in north-central Montana produced the igneous intrusive uplift complex which resulted in the emergence of the Bearpaw Mountains and the Sweetgrass Hills. Rivers carrying the mechanically weathered rock from this intrusive complex ended the erosion of the Ravenscrag Formation with the fluvial deposition of coarse gravel, and sand creating the youngest formation in the stratigraphic sequence of the Cypress Hills, the Cypress Hills Formation.
The Frenchman-Ravenscrag (K-T) boundary is at the base or within the basal Ravenscrag lignite/anthracite coal seam and represents a regional and global paleoclimate change along with what is perceived as a major extinction event. The local site “Hwy 37”, south of Shaunavon, SK below the 1.5 m Ferris No.1 coal seam offers one of the best exposures of the K-T boundary in North America.
The 1-2 cm wide K-T boundary clay deposits first came to light in 1980 when a team of researchers, led by Luis Alvarez, traveled the world investigating this unusual boundary. The shocked quartz and high amounts of iridium in the boundary clay suggested the anomaly is associated with an impactor. Iridium is rare in the earth’s crust and is found with heavier elements along with iron near the earth’s core. Asteroids and comets have a higher abundance of iridium that can be used as an indicator element to determine whether the source of an event is terrestrial or extraterrestrial.
Sample of the 1 cm K-T boundary clay line at the T.rex Discovery Centre, Eastend, SK. Photo: Charles Kuss A large impact crater from an extraterrestrial source was discovered in the Gulf of Mexico during the late 1970s by geophysicists looking for oil. It wasn’t until 1991 when the impactor site was confirmed using commercial offshore oil drilling data and drill core analysis that this may be the possible cause of the K-T boundary anomaly, and that the impactor may have had a global paleoenvironmental significance. The large buried crater is located on the northern tip of the Yucatan Peninsula in the Gulf of Mexico near the town of Chicxulub, Mexico. At the time of the impact (65 Ma), the northern tip was underwater creating a massive tsunami with tsunami deposits discovered all around the gulf. Since then, ejecta deposits have been found at multiple land-based sites in North and Central America (Fig 3).
Figure 3: The Chicxulub impact site 65 million years ago. The white area is submerged land, from Kring (2019) Lunar and Planetary Institute.The impactor is believed to have been 10 km in diameter coming in at an angle of 45-60 degrees from the NE traveling 20+ km/sec creating a 240 km wide crater that’s 25-30 km deep. It’s believed the impact created a superheated plasma pulse of 10,000 C lasting a few minutes that created a shock wave and airburst sending material and steam high up into the atmosphere and around the globe. This material eventually settled down on the surface creating the K-T boundary clay deposit. Soot in the form of a black carbon layer is also common near and at the boundary suggesting massive global grass, brush, and forest fires.
The Chicxulub impact theory is the one most often cited as a possible cause of the massive K-T extinction where 75% of species disappeared because of severe environmental degradation. The earth has experienced a total of five mass extinction events with similar consequences, and now possibly a sixth (Fig. 4) may be underway in the last 100,000 years. The sixth event has an additional threat to life, past and current anthropogenic activities, including overhunting, pollution, and deforestation that have and are attributing to species habitat destruction leading to many species disappearing permanently.
Figure 4: A generalized geologic time scale. ‘Ma’ is an abbreviation for millions of years. The asterisks indicate major extinction events and the question mark asterisk is a possible major extinction event currently underway. Image modified after USGS.The impact theory which usually mentions an asteroid is popular but controversial. It’s not known whether the impactor was a comet or asteroid. The timing of the impact and the mass extinctions are also in question with evidence supporting possibly two impacts, one predating the K-T boundary by 400,000 years, and the other 100,000 years after the K-T boundary. Detailed stratigraphy and biotic analysis also seem to indicate the impactors themselves were not the cause of the mass extinctions. There is evidence of large amounts of soot worldwide before the K-T boundary that show signs of renewed vegetation growth. There is also the question of whether the dinosaurs died out suddenly at the K-T boundary or were already reduced in numbers and had died out long before the K-T boundary event.
Large cosmic impactors have upset the earth’s geological stability, disrupted numerous sensitive environments and ecosystems, and destroyed the food chain making it difficult for some species to survive. Species with a low tolerance to environmental change and a very narrow geographical distribution are the first to disappear. Those with higher tolerance and broader geographical range will survive until their tolerance threshold is reached and they too will disappear. Some species may become locally extinct, but survive elsewhere. There are hints of another cosmic disruptor in addition to comets and asteroids and for this, we need to look at a more recent event, the Younger Dryas event of 13,000 years ago.
To clarify a previous statement, there is no difference between the K-T and K-Pg boundaries. In 2008 the Tertiary Period was replaced with the Paleogene and Neogene periods (Fig. 4). Any articles written before 2008 use K-T, and articles written after 2008 use K-Pg. Since most of the articles in the sources are older than 2008, K-T is used and, when needed, can be substituted for K-Pg.
Sources:
Adatte, Thierry; Kramar, Utz; et al; https://www.academia.edu/8937549/More_evidence_that_the_Chicxulub_impact_predates_the_K_T_mass_extinction?auto=download&email_work_card=download-paper; Meteoritics & Planetary Science;Vol 39, No. 7; Pgs 1127-1144; 2004
Bamforth, Emily L.; (PDF) Log Jams and Juveniles: Unusual deposits at the K-Pg Boundary in the Frenchman Formation (66 Ma) of Saskatchewan, Canada (researchgate.net); Royal Saskatchewan Museum, T.rex Discovery Centre; Eastend, SK; September 2019
Bamforth, Emily L.; (PDF) The Triceratops 'Baby Book': An Update on Juvenile Ceratopsians from the Frenchman Formation (66 Ma) of Saskatchewan, Canada. (researchgate.net); Canadian Palaeontology Conference, Preceedings Vol No 15; Saskatoon, SK; September 2018
Bamforth, Emily L; Local environmental conditions drove vertebrate biodiversity immediately prior to the K/Pg Extinction: Evidence from Central Canada. | Request PDF (researchgate.net); Journal of Vertebrate Paleontology 72nd Annual Meeting, Programs and Abstracts: 59; October 2012
Binda, Pier L., et al; AAPG Datapages/Archives: STRATIGRAPHY, PALEONTOLOGY, AND ASPECTS OF DIAGENESIS OF THE WHITEMUD FORMATION (MAASTRICHTIAN) OF ALBERTA AND SASKATCHEWAN (Abstract); Sixth International Williston Basin Symposium, SP11; Pgs 179-192; October 7, 1991
Byers, P. N.; Mineralogy and origin of the upper Eastend and Whitemud Formations of south-central and southwestern Saskatchewan and southeastern Alberta (cdnsciencepub.com); Canadian Journal of Earth Sciences; Vol 6, No 2; Pgs 317-334; 1969
Corliss, William, R.; Anomalies in Geology. Physical, Chemical, Biological : A Catalog of Geological Anomalies (archive.org); The Sourcebook Project; Glen Arms, MD; 1989
Firestone, Richard; West, Allen; et al; The Cycle of Cosmic Catastrophes; Bear & Company; Rochester, VT; 2006
Furnival, G.M; Cypress Lake Map Area, Saskatchewan; GEOSCAN Search Results: Fastlink (nrcan.gc.ca); Geological Survey of Canada; Memoir 242; 1946
Geology - Cypress Hills Provincial Park | Alberta Parks; Government of Alberta; Edmonton, AB; June 28, 2017
Keller, Gerta, et al; Chicxulub impact predates the K-T boundary mass extinction | PNAS; The National Academy of Science; Vol 101, No 11; Pgs 3753-3758; March 16, 2004
Keller, G,; et al; Multiple Impacts Across the Cretaceous-Tertiary Boundary; doi:10.1016/S0012-8252(02)00162-9 (redciencia.cu); Earth-Science Reviews; Vol 62, Issues 3-4; Pgs. 327-363; Sept 2003
Kring, David A.; Chicxulub Impact Event; Chicxulub Impact Event (usra.edu); Lunar and Planetary Institute; Houston, TX; 2019
Kolaceke, Anezka; Velez, Maria I.; et al; (PDF) Lithostratigraphy of Sections in the Vicinity of the Excavation Site of a Nearly Complete Tyrannosaurus rex Skeleton (Scotty) in Southwestern Saskatchewan, Canada (researchgate.net); Saskatchewan Geological Survey; Summary of Investigations; Vol 1; Miscellaneous Report 2018-4.1, Paper A-6; 2018
Kupsch, W. O.; Geology of Eastern Cypress Hills (Knollys and Dollard Quadrangles); Publications Saskatchewan; Saskatchewan Geological Survey; Report 20; Regina, SK; 1956
Marsh, Arden; Berenyi, Jason; An Overview of Coals in Saskatchewan; Saskatchewan Ministry of Energy and Resources; Government of Saskatchewan; Regina, SK; https://www.bing.com/ck/a?!&&p=7741299d73ec00b5JmltdHM9MTY3MzY1NDQwMCZpZ3VpZD0yYTNiMmNmNC02YWUzLTYwNjUtMmJkMS0zZTljNmI0YjYxYzMmaW5zaWQ9NTE2OQ&ptn=3&hsh=3&fclid=2a3b2cf4-6ae3-6065-2bd1-3e9c6b4b61c3&psq=95116-OH2008_TS4_Marsh%2520%2520coal%2520reserves%2c%2520mines%2520sk.pdf&u=a1aHR0cHM6Ly9wdWJzYXNrZGV2LmJsb2IuY29yZS53aW5kb3dzLm5ldC9wdWJzYXNrLXByb2QvOTUxMTYvOTUxMTYtT0gyMDA4X1RTNF9NYXJzaC5wZGY&ntb=1 (downloads PDF); Site accessed 1-14-2023
McIver, Elisabeth E.; The paleoenvironment of Tyrannosaurus rex from southwestern Saskatcheewan, Canada; https://cdnsciencepub.com/doi/10.1139/e01-073; Canadian Journal of Earth Sciences; Vol 39, No 2; Pgs 207-221; 2002
O’Dale, Charles; CHICXULUB IMPACT STRUCTURE – Crater Explorer; Ottawa, ON
Plainsman Clays Ltd; Medicine Hat, AB; Plainsman Clays; Site accessed 1-12-2023
USGS; File: Geologic time scale; https://commons.wikimedia.org/wiki/File:Geologic_time_scale.jpg; Washington, DC; July 2010
Robin, C.M.I.; et al; NAD83v70VG: A New National Crustal Velocity Model of Canada; GEOSCAN: More Report (nrcan.gc.ca); National Resources Canada; Geometrics Canada Open File 0062; Ottawa, ON; 2020
Water Deposits; www.3.nd.edu/~cneal/PlanetEarth/Lab-Deserts/Depositional.html; University of Notre Dame; Notre Dame, IN, USA
Wikipedia, The Free Encyclopedia; Washington, DC; 2020
The
perpendicular joints of the Ravenscrag Formation 4 km SSW of Fort
Walsh, also known as the “Mystery Rocks”. The main structural
features in the Cypress Hills are joints. What causes joints to form
in rock is somewhat debatable, but in the Cypress Hills they may have
been created by the isostatic rebound related to erosional unloading
of the Cypress Hills Formation and/or the isostatic adjustments from
the many glaciations during the past 2.6 Ma. Today, northern Canada
that is still rebounding 5-8+ mm/year from the Wisconsin deglaciation
and the Cypress Hills and area is subsiding 2-3 mm/year. Photo:
Charles Kuss
Display of T. rex (Scotty) at the T.rex Discovery Centre. Photo: Charles Kuss
Triceratops display at the T.rex Discovery Centre. Discovered in the Frenchman Formation near Hwy 37. Photo: Charles Kuss
Large
well cemented concretionary “log” structures in the Frenchman
Formation along the Frenchman River valley. Photo: Charles Kuss
Chocolate Peak, approximately 2 km NW of Eastend, SK on grid road 614. According to local accounts, the red baked clay visible on the hillside is from a coal seam fire set by a Whitemud clay miner in the 1930s to get access to the clay. Apparently, the seam burnt for many months before extinguishing itself. Image: Charles Kuss
