Subsequent to the Last Glacial Maximum (LGM), complex coastal response
resulted from deglaciation, eustatic sea-level change, and a relatively thin, flexible
lithosphere in the Queen Charlotte Islands (QCI) region of northwestern Canada.
Presented here is an interdisciplinary study that combines the methodologies and schools
of thought from geology, biology, and geography to address a research problem that
spans these disciplines, specifically to illustrate the environment, temporal and spatial
dimensions of isostatic crustal adjustment and the Late Quaternary coastline of the
northeast Pacific continental shelf. Molluscan distribution, lithology, and published sub-bottom
profiles are used to deduce sea-levels, outline the influence of glacially-induced
crustal displacement, and reconstruct the paleoenvironment of the northeast Pacific Late
Quaternary coastline, including the absence of ice and the presence of emergent coastal
plains. These data are used to ascertain the region's suitability as a home for an early
migrating coastal people.
A series of paleogeographic maps and isostatic crustal displacement maps chart
the sequence of evolving landscapes and display temporal changes in the magnitudes and
extent of crustal flexure as a forebulge developed. The wave-length and amplitude of the
glacially-induced forebulge supports thermal and refraction modeling of a thin (~25 km
thick) lithosphere beneath Queen Charlotte (QC) Sound and Hecate Strait. Glacial ice at
least 200 m thicker than present water depth began retreating from Dixon Entrance after
14,000 and prior to 12,640 14C years BP, generating 50 m of uplift in northern Hecate
Strait. The position of the forebulge remained essentially constant after 12,750 14C years
BP, implying a fixed ice-front and continued ice presence on the British Columbia (BC)
mainland until ~10,000 14C years BP. A 3-dimensional model shows two ice-free
terrains emerged: one extended eastward from the QCI, the other developed in QC
Sound. By ~11,750 14C years BP a landbridge connected the BC mainland and QCI.
Malacological evidence indicates a paucity of Arctic molluscan faima subsequent
to glaciation, perhaps a consequence of shallow, narrowed straits, and the presence of ice
sheets that interfered with ocean currents. Water temperature, sedimentation rates,
turbidity, and photoperiod are factors that limited invertebrate colonization during the
Late Pleistocene - Early Holocene. The oldest dated mollusc to colonize QCI region
subsequent to LGM was Macoma nasuta at 13,210 14C years BP. Once habitat and sea-surface
temperatures were conducive, rates of recolonization appear to be limited only by
the availability of ocean currents to bring temperate pelagic larvae into the region from
outlying areas. Between ~11,000 and 10,000 14C years BP the appearance of
Clinocardium ciliatum and Serripes groenlandicus, concurrent with the disappearance, or
significant reduction in number and productivity of temperate intertidal molluscs,
indicates the onset of a short interval of cool sea-surface temperatures coincident with the
Younger Dryas cooling event. Five molluscan species: Macoma incongrua, Musculus
taylori (cf), Mytilimeria nuttallii, Tellina nucidoides, Mytilus edulis/Mytilus trossulus
previously categorized as possessing a Recent geologic range were collected in sediments
dating older than 10,000 14C years BP. Fossil mollusc shells indicate edible intertidal
biomass densities well within commercially harvested levels on southern Moresby Island
by 8,800 14C years BP, and on northern Graham Island by 8,990 14C years BP.
The presence and productivity of nutritious intertidal molluscs indicates the QCI
region had a suitable climate, possessed open ocean conditions, and provided subsistence
resources for potential early humans subsequent to at least 13,210 14C years BP. Three-dimensional
modeling shows subaerially exposed land that could have been inhabited by
plants, animals, including coastal-migrating early humans. Early coastlines that have not
been drowned, and which may harbour early archaeological sites, are identified along the
western and northern coasts of QCI and the BC mainland. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/10296 |
| Date | 13 November 2018 |
| Creators | Hetherington, Renée |
| Contributors | Smith, D.J., Barrie, J.V. |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | Available to the World Wide Web |
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