Geomorphology and sedimentology of the lower delta plain and subaqueous delta plain of the Athabasca River Delta, N.E. Alberta

• Main Author: Gorecki, Richard C.
• Other Authors: Smith, Derald G.
• Format: Master Thesis
• Language: English
• Published: University of Calgary 1990
• Subjects: Geomorphology - Alberta - Athabasca River; Sedimentation and deposition - Alberta - Athabasca River; Deltas - Alberta - Athabasca River; Athabasca River
• Online Access: http://hdl.handle.net/1880/101410; https://doi.org/10.11575/PRISM/409

Bibliography: p. 182-195. The Athabasca lower delta plain and subaqueous delta plain (lower Athabasca Delta) are mainly a product of fluvial influence and a shallow receiving basin. The geomorphology of the lower Athabasca Delta reflects these conditions, and is characterized by bifurcating, low-sinuosity distributary channels, muddy interdistributary basins, distributary mouth bars and a gently sloping offshore profile. The major sandy bodies within the lower Athabasca Delta are the product of deposition within the distributary mouth bar, the crevasse-splay and the infilling distributary channel. Distributary mouth bars form thin (less than 4 m), lenticular bodies which tend to coalesce and produce a semi-continuous sandy sheet along the delta front. Crevasse-splays similarly form lenticular bodies of coarse material, however, they are smaller in scale than distributary mouth bars and tend not to merge laterally with each other. Distributary channel-fills tend to consist of very clean sands, and may exceed 5.5 m in thickness. They form a bifurcating to anastomosing network, and display a broad Ushaped cross-section which may be up to 600 m wide. Channel infilling occurs due to vertical aggradation as well as through the process of limited lateral accretion. Vertical aggradation is due to bedfonn migration along the channel thalweg, and produces a uniform sand sequence. Limited lateral accretion involves the process of step-wise bar formation, and occurs diagonally as opposed to strictly vertically or laterally. This style of infilling produces three types of vertical sequence: rhythmic sand, mud and heterolithic.