Quaternary geology, Cape Breton Island, Nova Scotia

Abstract

Tertiary planation and uplift exhumed two unconformities (paleoplains) and produced two peneplains into which Quaternary glaciation excavated submarine basins and channels. The last interglaciation deposited organic beds and cut an intertidal rock bench and littoral gravel, now emerged 2-7 m. The nonglacial period spanned 126-47 ka BP according to 30 Th/U and 14C wood ages at 16 sites. Two temperate cycles climaxed 125 and 86 ka BP and are correlated to oxygen isotope substages 5e and 5a; the first had hardwood forest reflecting a warmer than present climate; the second had boreal forest like today. Early-Middle Wisconsinan time is recorded by three tundra/boreal forest alternations, reflecting climatic deterioration until Wisconsinan glaciers arrived 62-47 ka BP. Several ice flow phases left crosscutting striations, superimposed drumlins and fluting, and three main till sheets of differing lithology, colour, texture, and provenance. An ice cap began on the highlands, then an ice sheet from mainland Nova Scotia advanced eastward and deposited a red foreign till on the lowlands. South-flowing regional ice (Laurentide?) crossed the island; it was cold-based on the highlands and preserved preglacial soil and landforms. Weathered striations beneath fresh till suggest an ice free interval. A northward flow from Scotian Shelf which introduced shell fragments may have signalled an ice rise, a flow reversal due to drawdown, or a new ice dome on the emergent shelf. The ice divide shifted onshore forming a Bras d'Or Lake centre. Gulf of St. Lawrence ice on the west coast dammed lakes that drained northward. Climatic cooling 11-10 ka caused glacial readvance and renewed solifluction. Highland ice lasted until 8-9 ka and Neoglacial cirque glaciers may have formed. Neotectonics tilted the bench southward and displaced it 15 m at Aspy Fault. Submerged features, geodetic relevelling, and tide gauging show a relative sea level rise of 20-70 cm/100 a due glacial forebulge collapse. Unstable slopes have landslides and sagging cliffs.

The North structure: evidence for a second possible impact event at the Bloody Creek site, Nova Scotia, Canada

“…Both the North structure and nearby Bloody Creek structure are located on the Atlantic Uplands Peneplain. Late Cretaceous to Pliocene erosion of the peneplain is thought to have resulted in the offshore deposition of 1500 m of sand and gravel implying very significant erosion at both sites (Grant 1994;Stea and Pullen 2001;Wade and MacLean 1990). Peneplanation, therefore, likely pre-dated the formation of both structures because such large-scale erosion would have destroyed basin morphometry.…”

Sea-cliff Erosion with Rising Sea-Level along Shores Exposing Glacial Material in Atlantic Canada: The Effect of Bedrock Slope and an Example from Isle Madame, Nova Scotia

“…1), commonly as undulating 'whalebacks', locally still showing glacial striae (Stea et al 1992;Grant 1994). Indeed, the position of the shore generally depends on the protection provided by this bedrock in a stable state of temporary equilibrium relative to wave erosion, but rapid retreat of some adjacent shores show that even this apparent stability is fragile and transient.…”

Geology and Hydrogeology of Faults on Cape Breton Island, Nova Scotia, Canada: an overview

“…Although all of these processes have been ongoing to varying extent throughout the Quaternary, Grant (1990Grant ( , 1994 noted that evidence of Cenozoic crustal movement in Atlantic Canada is limited to rare, small, stepwise displacements of glaciated outcrops. The largest was an abrupt offset with 15 m upthrow along the south side of the Aspy Fault in Cape Breton Island sometime in the last 125 000 years.…”