Open File Report 2015-01

Open File Report 2015-01

OFR 2015-01

Synthesis of a Post-Laramide Stratigraphic Framework of the South Saskatchewan River Basin, Alberta, in Support of Hydrostratigraphic Modelling

Author(s) Hartman, G. Date 2015-05-20

An extensive literature review has enabled the synthesis of a post-Laramide stratigraphic framework of the South Saskatchewan River Basin (SSRB) in Alberta. This stratigraphy is the product of nearly continuous tectonic-fluvial processes (uplift, incision, and lateral planation) that have been punctuated by glacial events of both montane and continental provenance. The broad architecture of the landscape itself is a series of nested planation surfaces, including older remnant uplands and younger incised valleys, that represent an inverted stratigraphic column by which the relative stratigraphic position of the nonglacial deposits that mantle the surfaces may be assessed. The distribution and age determinations of glacial deposits that are intercalated among the planation surfaces complement the nonglacial stratigraphy such that both glacial and nonglacial stratigraphies can be integrated in a single post-Laramide stratigraphic framework for the region.

Conceptualization of the post-Laramide stratigraphic framework as an integrated product of nonglacial and glacial processes and recognition of the stratigraphic significance of the landscape architecture is shared between recent stratigraphers (post-1985) and pioneering geologists who first described the study area (pre-1955). In the intervening period, however, a radically different stratigraphic framework became the paradigm. In this alternate stratigraphic framework, tectonic-fluvial development of the study area was complete prior to the first glaciations. Consequently, the nonglacial and glacial stratigraphies are not integrated and cannot provide geometric or chronological references for one another.

This literature review shows that stratigraphies based on the alternate, non-integrated stratigraphic framework have not withstood scrutiny. Remarkably, however, stratigraphies developed prior to 1955, which are based on an integrated stratigraphic framework, are broadly similar to the current (post-1985) stratigraphies. The accomplishment of the earliest period of stratigraphic investigation is attributed to conceptualization of the stratigraphic framework of the SSRB as an integrated product of tectonic-fluvial development punctuated by glaciation.

The Alberta Geological Survey (AGS) intends to develop three-dimensional (3D) hydrostratigraphic models of the subsurface within the SSRB . It is anticipated that an integrated stratigraphic framework in which the stratigraphic significance of the landscape architecture is recognized will help constrain interpretation of post-Laramide sediments and corresponding hydrostratigraphic units in these models.