Late Wisconsinan McConnell glaciation (ca. 24-11 ka) occurred in four phases in the Pelly Mountains of southern Yukon. Phase 1 marked the onset of ice accumulation in cirques above 1524 m above sea level (a.s.l.). These local glaciers expanded and fed valley glaciers that extended into the surrounding lowlands (after 26.3 ka). At glacial maximum or phase 2, the development of ice-divides to the east and south of the Pelly Mountains permitted Cordilleran ice lobes to invade the lesser glaciated Pelly Mountains, which resulted in up-valley ice-flow. This ice-flow arrangement continued into early deglaciation (phase 3), a period characterized by re-advances of the invading ice lobes. Following retreat of the ice lobes from the Pelly Mountains, some local cirque glaciers above 1600 m a.s.l. resumed limited down-valley flow (phase 4). For drift prospecting purposes, the dominant glacial dispersion trajectory in these high relief areas is controlled by the last phases of ice-flow (either phase 3 or 4).

Glacial history reconstructions and geomorphic mapping in the North McQuesten River, Dublin Gulch, and Keno Hill map areas indicate a succession of less extensive glaciations. From oldest to youngest, the main glacial episodes are the pre-Reid (multiple glacial episodes), Reid and McConnell glaciations. The surficial geology of the study area is dominated by deposits of the Reid and McConnell glaciations. Pre-Reid glacial deposits are mostly confined to infrequent erratics on plateau areas above the Reid glacial limit. Glacial limit mapping indicates that ice flow patterns were similar in both the Reid and McConnell glaciations. Valleys aligned parallel with glacial ice flow are broad and U-shaped with significant glacial deposits in valley bottoms. In contrast, valleys aligned transverse to glacial ice flow are narrower and have a more V-shaped morphology. This relationship appears to be a controlling factor on the distribution of placers in the study area. Numerous drainages were analyzed for their placer potential in each of the three map areas. Their potential was based on geomorphic evaluations, glacial history, geochemistry, bedrock geology, and historic records. A concentration of potential placer creeks were identified in the Keno Hill/Mayo Lake area. Fewer prospective creeks were identified in the Dublin Gulch and North McQuesten River map areas.

Uplands in west-central Yukon supported alpine ice centres during the pre-Reid glaciations (Early Pleistocene). Subdued cirque forms are thought to be glacial cirques that have undergone degradation by nivation. The paleo-equilibrium line altitude (ELA) dropped as low as 1054 ± 96 m in the Crag Mountain upland (CMU). A pre-Reid age for the CMU cirques is based upon the presence of an Early-Middle Pleistocene paleosol in a moraine feature. Cirques in the Ogilvie Mountains provide proxy ELAs for the Reid (mean 1391 ± 132 m) and McConnell (mean 1488 ± 103 m) glaciations. Cirque glaciers did not form in CMU and most of Dawson Range during these later glaciations due to a decrease in precipitation. It is suggested that the progressive marginality of cirque glaciation through the Middle and Late Pleistocene may be related to the progressive enlargement of precipitation-diverting continental ice sheets east of the Cordillera.

The late Wisconsinan McConnell glaciation of the Big Salmon Range in the Pelly Mountains consisted of a four-phase ice-flow history. Phase 1 ice-flow consisted of local alpine glaciers advancing to the mountain front. During phase 2, or glacial maximum, the Cassiar lobe of the Cordilleran ice sheet advanced to the northwest and overtopped the range. Retreat of the Cassiar lobe during phase 3 of the glaciation resulted in ponding of meltwater in eastern drainage basins. The meltwater spilled over into western basins and caused significant erosion of surficial sediments. Phase 4 of the glaciation is marked by a limited late-glacial readvance of local alpine glaciers. This glacial history has several important implications for mineral and placer exploration in the area.

Preliminary investigation of surficial geology in northern Kluane Range has resulted in new interpretations of Pleistocene ice cover including extensive unglaciated terrain and restricted glaciation during the Last Glacial Maximum. Two glacial limits are identified: a higher limit recording the most extensive glaciation of the area; and a lower limit that records younger, less extensive glaciation. This paper describes Pleistocene limits of the Donjek Glacier and the distribution of surficial materials in the upper Quill, Maple, and Wade creek drainages. The source and transport mechanism of surface materials has particular significance for surficial geochemistry sampling programs and implications for mineral exploration are addressed.

Llewellyn Glacier contributes glacial meltwater to runoff entering the Yukon River, which flows through the hydroelectric power dam in Whitehorse, Yukon. An examination of lateral moraine stratigraphy, and radiocarbon and dendrochronological dating of in situ and detrital subfossil wood provide a record of fluctuations of Llewellyn Glacier over the past two millennia. Our data indicate the north lobe advanced sometime between AD 260 and AD 505, and reached within 70 m of its Little Ice Age maximum limit as early as the 17th century. The main lobe advanced as early as AD 1035, possibly between the First Millennium and Little Ice Age advances of the last two millennia, when glaciers have traditionally been considered more restricted. Results provide new information on the timing and frequency of fluctuations of Llewellyn Glacier, and can be used to assist with modelling the future impacts of climate change on glacial meltwater contributions to rivers and hydroelectric security in Yukon.

The nature and extent of past glaciations are depicted on the glacial limits map of Yukon.

Previously unrecognized glacial erosional landforms (i.e. cirques, u-shaped troughs, truncated spurs and arêtes, in order of increasing doubt), and glacial depositional landforms (i.e. end moraine and possibly ground moraine) occur in the Fifty Mile Creek area, west of the pre-Reid Cordilleran glacial limit. The cirques and end moraine, representing the best evidence of glaciation, are similar to landforms in the adjacent Yukon-Tanana uplands of Alaska and formed during the Eagle glaciation (>40 ka, or Reid in age). Glaciation caused climate-controlled variations in runoff and cycles of aggradation and incision in the Fifty Mile Creek drainage. This resulted in the formation of upper- and lower-level terraces along Fifty Mile Creek and its tributaries. The terraces are composed of slightly muddy, sandy gravel of locally derived lithologies, and are fluvial in origin. Placer gold occurs along Fifty Mile Creek and several of its tributaries, as well as in the lower-level terraces. The upper-level terraces are potentially placer-gold bearing.

Yukon Territory has been glaciated by Cordilleran and montane glaciers at various times throughout the Pleistocene, as well as by continental ice, the Laurentine Ice Sheet in the Late Pleistocene. Throughout the Late Cenozoic, each successive glaciation appears to have been less extensive than the previous one. In west-central Yukon the earliest glaciation occurred between 2.6 and 2.9 Ma. ago (Duk-Rodkin and Barendregt, 1997). This glaciation was the most extensive and formed a continuous carapace of ice covering all the mountain ranges, except for a small area of Dawson Range and a more extensive area in northern Yukon. The Mid Pleistocene Cordilleran glaciation was less extensive than older glaciations but it formed an extensive ice sheet covering most of the northern Cordillera. The Late Pleistocene glaciation was the most restrictive and formed a continuous carapace of ice from the continental divide to the Saint Elias Mountains, but only restricted ice caps formed on the Ogilvie Mountains. During the last glaciation, the Laurentide Ice Sheet, flowing from the east, reached the northeast part of the Yukon Territory ca. 30 ka ago. Distributed from [GeoYukon](https://yukon.ca/geoyukon) by the [Government of Yukon](https://yukon.ca/maps) . Discover more digital map data and interactive maps from Yukon's digital map data collection. For more information: [geomatics.help@yukon.ca](mailto:geomatics.help@yukon.ca)

Throughout the Pleistocene epoch, Yukon was repeatedly influenced by glacial ice originating from the Cordilleran Ice Sheet and independent alpine glaciers. The penultimate limit in Yukon has garnered controversy in recent years, as moraines in the central region of the territory were found to be older (MIS 6) than moraines in the southwest part of the territory and Alaska (MIS 4). The Ogilvie Mountains, located east of Dawson City, have proven especially problematic for chronological studies. This study will attempt to test a relatively new dating method on penultimate surfaces in the Ogilvie Mountains; Chapman Lake is the primary study area. Using a vertical sampling method to construct a cosmogenic depth versus concentration profile in outwash gravel, this research will determine whether Marine Isotope Stage 4 or 6 provided the conditions necessary for ice nucleation to build the penultimate glacial surface. The age calculated by the depth profile is supported by radiocarbon ages and macrofossil samples, optically stimulated luminescence ages, TCN boulder dating, as well as detailed stratigraphy of significant sites near the Chapman Lake moraine. The results will help determine the effects of climate forcing in this region and its relationship to the existing glacial framework of the territory.