P. F. Karrow’s research while affiliated with University of Waterloo and other places

We present a multi-proxy study of environmental conditions during and after the recessional phases of pro-glacial Lake Algonquin in the vicinity of the North Bay outlet, Great Lakes Basin. Data presented comes from a new sedimentary profile obtained from the Balsam Creek kettle lake c. 34 km northeast of the city of North Bay. This site lies close to the northeast margin of the maximum extent of the post-Algonquin lake sequence, which drained through the Ottawa-Mattawa valley system. Our data are presented against a Bayesian age-depth model, supporting and extending regional understanding of vegetation succession in this part of northeast Ontario. The core profile provides a minimum age for the formation of the glacial outwash delta in which the kettle is set, as well as tentative timing for the Payette (post-Algonquin) lake phase. We highlight two discrete intervals during the Early Holocene, with modelled mean ages of: 8475-8040 cal. BP (332-316 cm) and 7645 cal. BP (286 cm), when climatic aridity affected the growth of vegetation within the kettle vicinity. Association with volcanic activity is posited. Cryptotephra dating to 7660-7430 cal. BP (mean age: 7580 cal. BP) is chronologically and geochemically assigned to the Mazama climactic eruption, while an earlier ash accumulation 8710-7865 cal. BP is tentatively sourced to an unknown eruption also in the Cascades region of Oregon. Outside of these periods, the Balsam Creek sequence shows considerable habitat stability and a character akin to that seen at more southerly latitudes. On this evidence we propose that access to reliable resources within kettle features could have aided the initial colonisation of northern Ontario's environmentally dynamic early post-glacial landscape.

Detailed studies of coastal cliff exposures through two end moraines form the basis for a model of ice-marginal sedimentation in large ice-contact glacier-fed lakes. The input to the ice-marginal environment directly from the glacier included subglacial till and subaquatic flow tills. The subaquatic flow till (thinly bedded diamicton) was deposited in an apron (up to 1 km wide) along the ice margin. An upward gradient of pore-water pressure immediately beyond the ice margin, causing heaving and dilation of the sediments, initiated debris flows of glacially derived debris (subaquatic flow tills). Most of the stratified sediments in the ice-marginal zone entered the lake by way of a large proglacial stream. Sedimentation was dominated by quasi-or near-continuous density underflows that resulted in the deposition of a sequence of thick rhythmites. The glacier in the Lake Erie basin most likely behaved like an ice stream, with its movement controlled predominantly by a deforming bed of glacial debris, separating the glacier sole from underlying predeposited sediments. The deforming bed is preserved as a massive diamicton layer, interpreted here as subglacially deposited till.

Nonglacial deposits of Middle Wisconsin age are being discovered with increased frequency across a broad region of southern Ontario, Canada, and provide strong evidence for a time of significant ice withdrawal from the lower Great Lakes region. With each new discovery, a refined understanding of regional climatic and paleoecological environments is emerging. In this paper, we present the results of a sedimentological and paleoecological study of a subtill organic deposit in Zorra Township, southwestern Ontario. The organic deposit, which lies beneath Nissouri Phase Catfish Creek Till (Late Wisconsin), has been dated by accelerator mass spectrometry at between 50.5 and 42.914C ka BP. The organic remains are contained within slack water pond deposits infilling a channel incised into till either of Early Wisconsin or Illinoian age. The fossil assemblage appears to be strongly influenced by taphonomic processes, including degradation due to oxidation, bacterial and fungal decay, and glacial overriding. Reworking and (or) recycling and selective sorting as well as long-distance transport has also influenced the composition of the fossil assemblage preserved. Nonetheless, meaningful paleoecological information is still obtained from this record. Collectively, the pollen and plant macrofossils indicate a boreal-type pine–spruce forest with temperatures cooler than present. The absence of arctic tundra plants, as are found in many other deposits of similar age in the lower Great Lakes basin, is notable. A pond or wetland inhabited by shoreline herbs, shrubs, and trees was present at or proximal to the site. The freshwater mollusc and ostracode assemblages are consistent with a shallow water habitat with dense submerged vegetation. The terrestrial mollusc assemblage suggests a taiga or transitional taiga–tundra fauna. Together, these fossil groups provide one of the most comprehensive environmental reconstructions of Middle Wisconsin time (oxygen isotope stage 3 or OIS3) in southern Ontario and serve to build on the ever-increasing database of paleoecological information accumulating for this episode of the late Quaternary. © 2015, National Research Council of Canada. All Rights Reserved.

The exposures at the St. Marys Cement Inc. quarry at St. Marys, Ontario, have been studied by geologists since the mid-1950s. This paper summarizes previous and new information collected in 2009, 2010, and 2012 and discusses the record of sediments resting on the bedrock surface that have been exposed during quarry operations. The exposed sediments illustrate the dynamic behavior of the Laurentide Ice Sheet in this area during the Late Wisconsin. Evidence for subglacial meltwater activity, shifting ice-flow directions during till deposition, a local or regional erosion event, possible subaerial exposure, and ice-marginal sedimentation is observed in the sequence of tills and stratified sediments exposed in the quarries. It also highlights how rapid lateral facies changes, complex contact relationships, and steep erosional contacts can prove to be challenging for correlation and extrapolation of subsurface units into three-dimensional stratigraphic models. Fourteen units were identified of which the lower six were deposited during the Nissouri age (Catfish Creek Drift). This included five layers of till deposited by a glacier that alternated from flowing out of the Lake Huron basin to that of a regional flow to the south-southwest. An angular unconformity cuts into these sediments and separates them from a finer-grained sediment sequence (primarily of Port Bruce age) consisting of glaciofluvial gravel, two fine-textured till layers, and rhythmically bedded glaciolacustrine sediments, all overlain by the uppermost till, the Rannoch Till, and Mitchell Moraine ice-marginal fan sediments.

Northern Grey and Bruce counties are situated centrally in the Lake Huron basin of the Great Lakes area of North America and are similarly central to the area of glacial Lake Algonquin, the largest glacial lake of the Great Lakes area. Ten survey traverses at sites in northern Grey and Bruce counties have documented the continuation of Lake Algonquin and Nipissing phase shorelines onto the Bruce Peninsula from previous work to the east. The Algonquin shoreline near 240 m ASL (above sea level) rises northward above land high enough to record it near Lion's Head. The Nipissing shoreline at 191 m ASL defines a shallow strait across the Bruce Peninsula near Ferndale, which was flooded temporarily at the maximum of the Nipissing transgression, separating northern Bruce Peninsula from the mainland. Uplift and Port Huron outlet downcutting later rejoined the island to the mainland as it is today. Raised beaches define Algonquin and Nipissing regressions by uplift using the Port Huron outlet. Paleobiotic records in a sand dune at Oliphant (molluscs), a Nipissing shorebluff along Sucker Creek (molluscs) and several sites in the former Nipissing shallow water strait near Ferndale (molluscs, ostracodes, plant macrofossils), provide paleoenvironmental data and supplement prior pollen studies at Lake Charles, Slough of Despond, and Hope Bay. Lake Algonquin deep water rhythmite clays are barren of fossils, whereas Nipissing shallow water silts are fossiliferous.

The occurrence of abandoned shoreline bedrock erosional features at the edge of the Niagara Escarpment at Cabot Head indicates the existence of a group of islands in glacial Lake Algonquin during early postglacial time, referred to herein as the Cabot Head Archipelago. The abandoned shoreline features are situated as much as 80 m above the level of contemporary Georgian Bay. The range of abandoned shoreline bedrock erosional features, including shoreline cliffs, adjacent wave-cut platforms, wave-cut notches, shore stacks, shore caves, and other features, are described. The occurrence of these features is thought to be the result of the interaction between wave action in glacial Lake Algonquin and two distinct lithological facies representing the Wiarton – Colpoy Bay and Lions Head members of the Amabel Formation. The exceptional development of the abandoned shoreline bedrock erosional features in massive reefal dolostone between elevations of 250 and 255 m above sea level (asl) is interpreted as representing the relatively long-lived and stable Main stage of glacial Lake Algonquin (11 000–10 200 years BP). Shoreline erosional forms at elevations between 240 and 250 m asl may be indicative of declining lake levels partially controlled by bedrock structural factors. The final abandonment of the glacial Lake Algonquin shoreline in this area occurred when the eastern outlets of the lake became ice-free and its level dropped rapidly some 10 200 years BP. The Cabot Head Archipelago and the associated suite of raised and abandoned shoreline bedrock erosional features represent a rare assemblage of landforms within the Great Lakes basin, and possibly within Canada.

Remains of single individuals of a juvenile gray fox (Urocyon cinereoargenteus), an eastern chipmunk (Tamias striatus), and a meadow vole (Microtus pennsylvanicus) have been recovered from a buried soil horizon at Scarborough Bluffs, Toronto, Ontario. These have been dated on associated charcoal fragments at 5550 ± 70 C14 years ago. The charcoal has been identified as being derived from white pine (Pinus strobus), hard maple (either Acer saccharum or A. nigrum), and probably beech (Fagus grandifolia). This faunal evidence is considered approximately contemporaneous with a fauna from Hamilton Bay containing the pine vole (Pitymys pinetorum) and the presence of the pine vole and gray fox is adduced as support for a climatic optimum some 5000 years ago. Remains of the muskrat (Ondatra zibethicus) have also been recovered from the Hamilton Bay faunal site, adding another mammal to this faunal list.

When Lake Iroquois drained between 11.7 and 11.4 ka BP, lake level in the Ontario basin fell from a high of more than 40 m above present lake level to a minimum close to the then-existing sea level, which was approximately 40 m below present sea level. Since that time, lake level has been rising at an exponentially decreasing rate in the western portion of the basin as a result of postglacial and neotectonic uplift of the outlet near Kingston, at the eastern end. The published lake level history has been combined with other less well-known parameters (the post-Iroquois regional topography, erosion – deposition rates, and distribution of resistive shore materials) to reconstruct the evolution of the western Lake Ontario shoreline. Borehole, long piston core, and other subsurface data sources, primarily from the western portion of the lake near Hamilton Harbour, provide most of the physical constraints. Time references were provided by radiocarbon dates on shallow-water organics in the subsurface sediments. A computer program was designed to calculate and contour the changing elevations of the rebounding post-Iroquois topographic surface, allowing the time-dependent water-plane elevation to be superimposed. Semiquantitative allowance was made for differential erosion and deposition along the advancing shoreline. The reconstruction provides a perspective on past and future shoreline evolution in the basin and possibly on the location of potentially commercial offshore deposits of aggregate.

A sand pit at Leamington, Ontario, in southeastern Essex County in the southernmost part of Canada, has yielded many taxa of fossil animals and plants that are dated over 13 000 BP. The fossils are of both terrestrial and freshwater origin, and comprise a surprisingly diverse but coherent assemblage of molluscs, ostracodes, Chironomidae, Coleoptera, Turbellaria, Trichoptera, and a few fish bone fragments. This is the oldest known postglacial occurrence in Ontario for all animal groups. Paleoenvironments indicated by the taxa range from boreal forest to tundra; taxa are an in situ assemblage with little transport or reworking. Although this site has yielded the richest fossil record of this age yet found in Ontario, previous finds at a few sites on the north edge of the eastern Erie basin and in the southern Huron basin indicate plants were well established in southwestern Ontario by the time of the Mackinaw Phase interstadial when lowered lake levels likely facilitated their arrival from land areas to the south. This discovery greatly improves the prospects of finding fossils of this age even though the known record is still extremely limited. The site represents fortuitous preservation and discovery, and amply demonstrates that glacial lakes of this time, when much of the last ice sheet was still in existence, were far from barren of life and that the migration of biota into the area was quite rapid during ice retreat.