Characteristics of Marine versus Continental Deposits in the Campanian Arctic: Examples from the Prince Creek–Schrader Bluff Transition, Toolik River, North Slope, Alaska
Peter Flaig, Trystan Herriott, Marwan Wartes, Dolores van der KolkCampanian deposits of the Prince Creek and Schrader Bluff Formations along the Toolik River, North Slope, Alaska provide an ideal example of lithofacies and ichnologic changes recording progradation and retrogradation of deltaic shorelines. Outcrops of strata this age in northern Alaska are rare, providing a unique window into paleo-Arctic ecosystems.
The top <5 m of the middle Schrader Bluff Formation is fortuitously exposed at the study site, comprising low-angle parallel-laminated sandstone with abundant Schaubcylindrichnus representing proximal delta front mouth bar deposits. Contrastingly, the overlying lower Prince Creek Formation comprises trough-crossbedded to current-ripple laminated fine-to medium-grained sand-rich point bar deposits of meandering rivers, current-ripple to parallel-laminated fine-grained sandstones with rare rhizoliths recording deposits of crevasse splays and levees, silty/muddy paleosols evidenced by abundant carbonaceous rhizoliths and rare dinosaur footprints (punch-downs), coals (swamp), and bentonites (ashfall). Rare Teredolities on logs indicates nearshore deposition.
A flooding event and delta retrogradation is evidenced by basal deposits of the overlying upper Schrader Bluff Formation, dominated by swaley to hummocky cross-stratification from the medial to distal delta front, and proximal mouth bar deposits similar to the middle Schrader Bluff. The bulk of upper Schrader Bluff lithofacies and ichnology are highly diverse, including highly bioturbated intervals with 10+ traces of marine affinities. Deposits also contain detailed brittle star impressions, and a single horizon containing abundant glendonites.
Toolik River Prince Creek and Schrader Bluff Formation deposits offer a rare glimpse into the deposystems and paleoecology of high-latitude, deltaic shorelines of Arctic Alaska that developed under a greenhouse climate.