Depositional environment Hell Creek Formation

the dominant plants of hell creek formation flowering plants.

it series of fresh , brackish-water clays, mudstones, , sandstones deposited during maastrichtian , danian (respectively end of cretaceous period , beginning of paleogene) fluvial activity in fluctuating channels , deltas , occasional peaty swamp deposits along low-lying eastern continental margin fronting late cretaceous western interior seaway. hell creek formation, typified exposures in fort peck area of montana, has been interpreted flat, forested floodplain relatively subtropical climate supported variety of plants ranging angiosperm trees conifers such bald cypress, ferns , ginkgos. hell creek formation laid down streams, on coastal plain along edge of western interior seaway. presence of crocodilia suggests climate subtropical; there no cold season , ample precipitation.

the hell creek formation, lance formation , scollard formation represent different sections of western shore of shallow sea divided western , eastern north america during cretaceous. swampy lowlands habitat of various animals, including dinosaurs. broad coastal plain extended westward seaway newly formed rocky mountains. these formations composed largely of sandstone , mudstone have been attributed floodplain, fluvial, lacustrine, swamp, estuarine , coastal plain environments. hell creek best studied of these ancient environments. @ time, region subtropical, warm , moist climate. climate humid, flowering plants, conifers, palmettos, , ferns in swamps, , conifers, canopy, understory plants, ash trees, live oak , shrubs in forests. in northwestern south dakota, strips of black layers deposited in wetland environment rich in coal, , bright band-like layer of sand , mud river floodplain accumulated. many plant species supported, angiosperms, , less commonly conifers, bald cypress, ferns , cycads. abundance of fossil leaves found @ dozens of different sites indicating area largely forested small trees.