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TitleCretaceous clastic basins of southern Yukon: the Alberta-Alaska dinosaur highway?
AuthorHaggart, J W; Ryan, J J; Sweet, A R; Bell, K M
Source12th British Columbia Paleontological Symposium, 2018, Courtenay, abstracts; 2018 p. 18-20
Alt SeriesNatural Resources Canada, Contribution Series 20180159
PublisherBritish Columbia Paleontological Alliance
Meeting12th British Columbia Paleontology Symposium; Courtenay, British Columbia; CA; August 17-20, 2018
Mediapaper; digital
File formatpdf
NTS95C; 95D; 95E; 105; 106B; 106C; 106D; 115; 116A; 116B; 116C
Lat/Long WENS-141.0000 -124.0000 65.0000 60.0000
Subjectspaleontology; stratigraphy; structural geology; sedimentary basins; structural controls; bedrock geology; lithology; sedimentary rocks; clastics; sandstones; siltstones; coal; conglomerates; mudstones; stratigraphic analyses; depositional environment; fossils; vertebrates; trace fossils; flora; microfossils; pollen; spores; Tintina Trench; Indian River Formation; Dinosaurs; Tintina Fault; Western Interior Seaway; Phanerozoic; Cenozoic; Tertiary; Mesozoic; Cretaceous
ProgramGSC Pacific Division
Released2018 08 01
AbstractSiliceous clastic deposits of late Early to Late Cretaceous ages are found widely but in localized exposures across southern Yukon, many within general proximity to the Tintina Trench. Some of these strata have recently been assigned to the Indian River Formation, with type locality based on successions preserved in outcrop and drill core collected from the valley of McKinnon Creek, tributary to the Indian River, which is itself a tributary of the Yukon River. A variety of trace fossil assemblages and palynological data have been documented previously in the McKinnon Creek core samples, suggesting that much of the Indian River Formation in that region is non-marine to marginal marine in nature and of general mid-Cretaceous age (Lowey and Hills, 1988).
We have examined outcrops of coarse clastic strata of southern Yukon assigned previously to the Indian River Formation in order to better qualify their age and depositional environments. No molluscan fossils have been found in these strata, but mudstone intervals within the successions have produced microfossils of pollen and spores indicative of non-marine environments. These fossil flora confirm that Albian-Cenomanian and Campanian-Maastrichtian ages are present within the Indian River Formation at the type area, as well as in lithologically-similar strata found at several other localities of southern Yukon.
Strata similar in age to the McKinnon Creek succession are known from several widely distributed areas of southern Yukon, from the valley of Sixtymile River on the northwest and near the Alaska border west of Dawson City, to Ross River on the southeast side; these strata appear to be localized along the course of the Tintina Trench. Although most of these strata lack any age control, the bulk of them are considered to be of Paleocene age (Hughes and Long, 1980; see Colpron, 2011 for latest summary). Among these "Paleocene" outcrops, the exposures at Ross River were found to be of mid-Cretaceous age, based on the presence of dinosaur tracks as well as palynological analysis (Long et al., 2001). The Ross River strata are thus of slightly older age than Campanian dinosaur-bearing strata of the Denali Park area of central Alaska (Fiorillo et al., 2014, 2018).
The lithologies - sandstone, siltstone, coal, conglomerate - of the "Paleocene" strata mapped along the course of the Tintina Trench between Ross River and Dawson City suggest that at least some of these strata may also be of Cretaceous age and correlative with the Ross River dinosaur track-bearing strata as well as other outcrops of the Indian River Formation. If movement along a proto-Tintina Fault started in Albian (late Early Cretaceous) time, then structural controls along the fault may have produced localized basins for subsequent accumulation of these non-marine strata. We envision a low-level valley system along the proto-Tintina fault, occupied by connected non-marine basins in mid-Cretaceous time, a possible Alberta-Alaska "dinosaur freeway" allowing transit of large vertebrates from the beaches of the Western Interior Seaway to those of central Alaska.
Summary(Plain Language Summary, not published)
This is an abstract of a scientific paper being presented at a paleontology conference. The authors have studied rocks of southern Yukon Territory and the fossils they contain and have established that many of these rocks formed in basins of terrestrial origin during times of equable climate, and possibly at times when the dinosaurs were prevalent in western North America. The authors suggest that dinosaurs may have travelled from Alberta to Alaska via these localized basins.

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