| Summary: | Title: Sedimentology and Allostratigraphy of Falher Memebers A and B of the Lower Cretaceous Spirit River Formation, Northwestern Alberta, Canad, Author: Richard G. Rouble, Location: Thode The 10 to 30m thick coarsening-upward sandbody successions of Falher Members A and B of the Lower Cretaceous (Early Albian) Spirit River Formation in northwestern Alberta are each split by a mudstone tongue at the seaward end. This mudstone tongue can be correlated landward with an abrupt grain size change within the main sandbody succession, where cross-bedded sandstones or conglomerate overlie swaley cross-stratified sandstones. The grain size change can be correlated with the top of a regionally extensive coal landward of the sandbody. The mudstone tongue and grain size change represent a marine flooding surface that splits each existing Falher member into two separate allostratigraphic units. Each of the four allomembers now recognized (A1, A2, B1, B2) was deposited as a barrier-strandplain system. The transgressive systems tract is preserved as barrier sands, transgressive successions consisting of coastal plain to lagoonal deposits, and transgressive lag deposits. The lagoonal and lag deposits were partially preserved seaward of the barrier during shoreface retreat. The transgressive systems tract also includes an estuary fill and onlapping transgressive offshore storm deposits. The highstand systems tract comprises a shoreface succession which prograded as a strandplain formed of sandy and gravelly beach ridges. Backspit lagoons are locally encased in the shoreface sands. In most allomembers, the beach conglomerate trends parallel to the barrier, on the seaward side. In existing Falher member B, a lowstand systems tract is represented by a south-north trending channel incision (Allomember B3) that cuts into shoreface deposits of Allomembers B1 and B2. This channel incision was probably feeding a lowstand wedge to the north. Each transgressive-regressive allomember has an estimated duration of approximately 305,500 years. The changes in relative sea level during deposition of the allomembers may have been controlled by combined allocyclic and autocyclic processes. Thesis Master of Science (MS)
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