Paleoenvironmental interpretation and depositional process classification of allomembers D and E, lower Horseshoe Canyon Formation, Alberta, Canada

摘要

Outcrops of allomembers D and E of the Late Cretaceous, Horseshoe Canyon Formation comprise marginal-marine units deposited on the western margin of the Western Interior Seaway. Associated facies are grouped into seven element complexes (EC; equivalent to facies associations) and 3 larger-scale element complex assemblages (ECA; equivalent to a depositional setting). Allomember D is classified as a tide-dominated, fluvial-influenced (Tf) ECA, and comprises two element complexes: Tf-tidal flat EC and F-onshore EC. Allomember E1 forms a tide-dominated, fluvial-influenced, wave-affected (Tfw) ECA that is composed of four ECs: Twf-tidal flat, Ft-channelized-A, Ft-channelized-B and F-onshore ECs. Allomember E2 forms a wave-dominated, tide-influenced, fluvial-affected (Wtf) ECA that consists of four ECs: Wtf-lobe, Wft-mouthbar, Tf-tidal flat EC and F-onshore ECs. Through classification of the element complexes within the allomembers, lateral and vertical changes in hydraulic processes are recorded and analyzed, highlighting the depositional variability within single parasequences and between parasequence sets in marginal-marine environments.