Rudolph R. Stea

The appalachian glacier complex in maritime canada

Large, local ice centers, collectively termed the Appalachian Glacier Complex, developed in Maritime Canada during the Wisconsinan glaciation, effectively barring Laurentide ice from the region. These ice centers shifted in time and space producing palimpsest glacial landforms including cross-striated bedrock outcrops and lobate drumlins. The glacial flow history of the region was deciphered from erosional glacier features (erosional stratigraphy) and till sheet provenace (depositional stratigraphy). Based on provenance, offshore glacial sediments were correlated to their terrestrial counterparts, establishing crucial links between ice flow patterns on land and ice margins offshore. From these empirical data five major flow patterns or ‘phases’ were defined along with their offshore margins. During the Caledonia Phase in the Early to Middle Wisconsinan, eastward to southeastwardflowing ice from Appalachian upland sources crossed Nova Scotia and extended out to the continental shelf edge where a calving margin was established. Submarine mass-wasting at this margin produced wedge-shaped bodies of diamicton that interfingered with glaciomarine sediments. The Caledonia Phase glacier retreated during the Middle Wisconsinan to the inner Scotian Shelf. During the Escuminac Phase in the Late Wisconsinan (22–19 14C ka) an ice centre formed over the Magdalen Shelf (Escuminac Ice Centre) and transported large quantities of local red bed material southward to the outer shelf/slope margin. Just after 18 14C ka, (∼21 CAL) the Escuminac Phase glacier configuration was re-organized by northward-flowing ice streams into marine channels bordering the Magdalen Shelf and an ice stream draining the Bay of Fundy into a divide over Nova Scotia (Scotian Ice, Divide-Scotian Phase). The Scotian Phase glacier margin offshore is marked by the Scotian Shelf End Moraine Complex dated between 17 and 14 14C ka (∼20 and 16.7 CAL). Between 13.5 (∼16 CAL) and 12.0 14C ka (∼14 CAL) the Scotian Ice Divide segmented into local terrestrial ice centers (Chignecto Phase) as a calving bay developed in the Bay of Fundy. These local centers advanced and retreated, responding to mass balance changes during a time of rapidly changing Northern Hemisphere climates. Responding to increasing climatic warming after 12 14C ka (∼14 CAL), the Chignecto Phase glaciers dissipated and their margins retreated landward. Isolated marine and terrestrial remmants of the Chignecto Phase glaciers re-advanced significantly during the Collins Pond Phase (Younger Dryas) ca. 10.8 14C ka (∼13 CAL).

Age of the five islands formation, Nova Scotia, and the deglaciation of the Bay of Fundy

Abstract Three atomic mass spectrometry (AMS) dates have been obtained for shell material from the bottomset beds of a glaciomarine delta at Spencers Island, Nova Scotia, near the head of the Bay of Fundy. The sediments in the delta are part of the previously undated Five Islands Formation, and are the first direct indictaion of the age of deglaciation in this region. The dates range from 14,300 to 12,600 yr B.P. and record the duration of deposition of a diamicton under the deltaic deposits and of the delta itself. The diamicton may have formed around 14,000 yr B.P. under ice-shelf or calving-bay conditions, or by a readvance of grounded ice. The Spencers Island delta is part of a prominent ice-marginal stand marked by numerous deltas along the Minas Basin. The time of formation of the deltas and the inferred ice margin is between 13,500 and 12,000 yr B.P. based on the Spencers Island dates and palynologically confirmed dates on the base of lake-sediment cores from the delta surface. Ice-marginal glaciomarine deposits near St. John, New Brunswick, record a range of radiocarbon dates similar to the Spencers Island dates. This implies that the Bay of Fundy became virtually ice free about 14,000 yr B.P.

Chapter 48 – The Appalachian Glacier Complex in Maritime Canada

Large, local ice centres, collectively termed the Appalachian Glacier Complex, developed in Maritime Canada during the Illinoian and Wisconsinan glaciations (MIS 6, 4-2), effectively barring Laurentide ice from much of the region. These ice centres shifted in time and space, producing palimpsest glacial landforms including cross-striated bedrock outcrops and lobate drumlins. Major flow patterns or ‘phases’ linked with ice divides termed the Caledonia, Escuminac, Scotian Chignecto, Shulie Lake and Collins Pond phases were defined along with their offshore and terrestrial margins.