Early to Late Campanian Palynological Ages of Mudstone and Siltstone in the Sawn Lake area, southern Buffalo Head Hills, Alberta

Palynological results are reported for six mudstone samples cored during an Alberta Geological Survey (AGS) auger-drilling program in the Sawn Lake area of the southern Buffalo Head Hills near the K4 kimberlite complex. Ages for these core samples, collected over an east-west distance of four kilometres, range from Early to Late Campanian (83.5 to 71.3 million years ago). The Late Campanian assemblages are indicative of (i) nonmarine fluvial-lacustrine, (ii) paralic and (iii) nearshore, restricted marine environments, whereas the Early Campanian assemblages reflect open marine conditions.

The Early Campanian ages are consistent with existing geological maps of the region that show the youngest rocks in the Buffalo Head Hills to be marine shales of the Smoky Group. However, the existence and distribution of sedimentary rocks with Late Campanian ages indicate that a significant part of the uppermost southern Buffalo Head Hills is underlain by rocks correlative to the Wapiti Formation. This is consistent with the presence of numerous sandstone units within the Upper Campanian auger core sections and the palynological change to a nonmarine (fluvial-lacustrine) depositional environment.

The Lower Campanian to Upper Campanian boundary occurs at a higher elevation than a bedded kimberlite unit on the flank of the K4 kimberlite complex. The bedded kimberlite is interpreted to be composed of volcaniclastic material derived from the K4 kimberlite complex. The stratigraphic relationships, assuming no major structural offsets, indicate eruption of the K4 kimberlite complex prior to the Late Campanian with subsequent burial of the kimberlite volcano by Late Campanian sedimentation.