. Bulletin of the British Museum (Natural History), Geology. BRYOZOANS FROM UPPER CRETACEOUS OF ALBERTA. CANADA 15 Canyon Formation of the Edmonton Group (Jackson et al., j 1981; Harvey et al., 1982; Irish, 1970; Stelck et al., 1972; Allan & Sanderson, 1945). The tongue is of early Maastrich- tian age, and thus is near (but not exactly at) the top of the Upper Cretaceous series here (Fig. 4). The regional stratigra- phy is characterized by diachronous intertonguing of the major lithofacies. These were deposited along a deltaic shoreline retreating southeastwards, but frequently fluctuat- i
. Bulletin of the British Museum (Natural History), Geology. BRYOZOANS FROM UPPER CRETACEOUS OF ALBERTA. CANADA 15 Canyon Formation of the Edmonton Group (Jackson et al., j 1981; Harvey et al., 1982; Irish, 1970; Stelck et al., 1972; Allan & Sanderson, 1945). The tongue is of early Maastrich- tian age, and thus is near (but not exactly at) the top of the Upper Cretaceous series here (Fig. 4). The regional stratigra- phy is characterized by diachronous intertonguing of the major lithofacies. These were deposited along a deltaic shoreline retreating southeastwards, but frequently fluctuat- ing locally in response to variations in sediment supply, coastal-ground compaction or subsidence, regional tecton- ism, and possibly also eustatic sea-level changes. The great bulk of the Edmonton Group is made up of the Horseshoe Canyon Formation, 275 m (900 ft) thick around Drumheller, and consisting of complexly interlensing and interbedded grey, tan and brown shales, mudstones, and soft sandstones, with scattered thin lenses of concretionary iron- stone and several beds of subbituminous coal. It is overlain by the thin Whitemud Sandstone, Battle Shale, and dinosaur- bearing Scollard Beds. It is underlain by the fully marine, but shallow water, dark-grey Bearpaw Shale, 150 m (500 ft) thick in this vicinity; their contact is an intertonguing transitional . zone, and the Drumheller marine tongue is simply a some- what later and more extensive part of this formational interface on a regional scale (Fig. 4). The Horseshoe Canyon ; Formation has yielded various continental fossils: dinosaurs, small vertebrates, freshwater molluscs, woody plants, and palynomorphs (Allan & Sanderson, 1945; Irish, 1970; Srivas- tava, 1970; Harvey etal., 1982; Gross, 1985). These indicate a humid subtropical climate at the time when Eokotosokum bicystosum inhabited the adjacent bays. Especially in its lower portion transitional into the Bearpaw Shale, the Horse-. Please note that these images are
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