A postglacial plant macrofossil record of vegetation and climate change in southern Saskatchewan

Catherine Yansa and J.F. Basinger

        The Andrews site is a small closed-drainage basin on the Missouri Coteau of southern Saskatchewan that has been filled with postglacial sediment.  Plant macrofossil analyses of 67 sediment samples and 6 14C ages were used to reconstruct 6 phases of environmental changes that followed deglaciation in southern Saskatchewan.  Fossil remains of 42 taxa of vascular plants have been recognized and are illustrated.  Sparse macrofossils recovered from the basal diamicton (Phase 1) are likely redeposited.  Abundant fossils indicate establishment of an open white spruce forest by ca. 10.2 ka BP (Phase 2), followed by development of a pond and replacement of the spruce forest by deciduous parkland vegetation (Phase 3) that persisted until ca. 8.8 ka BP.  The pond shallowed at the end of this period.  Prairie fires are evident between ca. 8.8 and 7.7 ka BP (Phase 4).  Water levels rose between ca. 7.7 and 5.8 ka BP and a semi-permanent prairie pond was established (Phase 5).  After 5.8 ka BP this wetland became ephemeral (Phase 6) and no longer conducive for fossil preservation.