A chronological framework for the Clyde Foreland Formation, Eastern Canadian Arctic, derived from amino acid racemization and cosmogenic radionuclides

Abstract

The most extensive terrestrial outcrops of glacial and glaciomarine deposits in the Eastern Canadian Arctic are exposed in sea cliffs along the Clyde Foreland and Qivitu Peninsula of Baffin Island. Collectively known as the Clyde Foreland Formation (CFF), these stacked deposits record at least seven glacial advances. Despite having been the focus of numerous investigations spanning nearly 50 years, no numerical chronological framework for the age of the deposits has been established. Previous studies relied on biostratigraphy and amino acid racemization (AAR) geochronology and postulated that the oldest units were Late Pliocene to Mid-Pleistocene in age. In this paper, we use a cosmogenic radionuclide isochron approach to determine a minimum age for the burial of a paleosol preserved within the CFF. Abundant palynomorphs in the paleosol are dominated by cool-climate taxa. Combining the paleosol burial age with a compilation of published and new CFF AAR data for marine bivalves Hiatella arctica and Mya truncata, we statistically define seven CFF aminozones and develop a piecewise isoleucine AAR calibration model for Baffin Island. From this, we estimate the minimum age of each aminozone, although the propagation of errors through all calculations produces large uncertainties for each age estimate. The youngest three CFF units, known as the Kogalu, Kuvinilk, and Cape Christian members, were most likely deposited during glaciations in the Mid- to Late-Pleistocene. The paleosol formed prior to 1.15 ± 0.20 Ma, and the underlying aminozones represent sedimentation during Early Pleistocene or latest Pliocene glaciations and record early advances of Laurentide ice across Baffin Island.

Introduction

The most extensive outcrops of superposed glacial and glaciomarine deposits in the Eastern Canadian Arctic are found along the northeastern coast of Baffin Island on the Clyde Foreland and Qivitu Peninsula (Fig. 1A). Exposed in wave-eroded cliffs are cyclical sedimentary facies deposited on coastal lowlands during successive glaciations (Miller et al., 1977; Nelson, 1981) collectively comprising the Clyde Foreland Formation (CFF; Feyling-Hanssen, 1976a; Andrews et al., 1985; Miller, 1985). During an individual sedimentation cycle, the growth of the Foxe Sector of the Laurentide Ice Sheet (LIS; Fig. 1A) isostatically depressed Baffin Island, and the resulting marine transgression inundated these lowlands. The deposition of silts and sublittoral sand continued until ice advances deposited distal- to proximal glaciomarine sediment, followed by till. As ice retreated, this sequence reversed, and pedogenesis began following a marine regression and reemergence of the coastal lowlands.

Exposures of Plio-Pleistocene sedimentary deposits are found throughout the North American Arctic and at locations around Greenland (Feyling-Hanssen et al., 1983; Funder et al., 2001; Bennike et al., 2002, 2010), northern Alaska (Brigham-Grette and Carter, 1992), and scattered sites across the Arctic Archipelago (Brigham-Grette et al., 1987; Matthews, 1989; Vincent, 1990; Devaney, 1991; Fyles et al., 1998). However, the majority of previously studied marine sediment deposited during eustatic marine transgressions and provides only limited information about past glacial advances and marine conditions during glaciations. Additionally, most of these deposits span only brief intervals of time and interpretations are hampered by ambiguous chronologies. In contrast, the CFF contains a sedimentological succession of seven distinct major Quaternary continental glaciations, as well as a paleontological record of conditions during each of these intervals.

Since Goldthwait (1964) first described these deposits, the CFF has been the subject of investigations of micropaleontology (Feyling-Hanssen, 1976b, 1980, 1985; Feyling-Hanssen et al., 1983), aminostratigraphy (Miller et al., 1977; Mode, 1980; Nelson, 1982; Miller, 1985), sedimentology and stratigraphy (Løken, 1966; Mode, 1980; Nelson, 1981), facies changes (Nelson, 1981), and palynology (Miller, 1976; Mode, 1980). These studies were all limited by the inability to reliably apply any absolute dating tools to the CFF. Absolute dating efforts, some of which were ineffective (Kaufman et al., 1993), have only succeeded in placing minimum-limiting age estimates on some of the deposits using radiocarbon and U-series methods, the results of which suggest the oldest deposits are >300 ka (Szabo et al., 1981). Using amino acid racemization (AAR) measurements and a range of probable effective diagenetic temperatures (EDTs), Miller (1985) suggested that the oldest aminozone is likely 1.6 to 7.9 Ma, and Feyling-Hanssen (1985) inferred a latest Pliocene or Early Pleistocene age for the oldest CFF sediments from tentative biostratigraphic correlations to dated Plio-Pleistocene deposits elsewhere in the Arctic.

Despite the prodigious body of prior CFF research, the resulting detailed micropaleontological record, and the presence of some of the oldest deposits from major LIS advances, we still lack a reliable chronological framework for these sediments. In an effort to make headway into this problem, we apply a cosmogenic radionuclide (CRN) isochron burial dating technique (Balco and Rovey, 2008) to a newly identified paleosol preserved within one of the oldest aminozones of the CFF (Fig. 1B). By using the resulting minimum age to calibrate AAR, we present a refined chronology for the CFF. We also analyzed the palynomorphs within the paleosol, which provide a glimpse into the climate during an Early Pleistocene interglaciation and coastal sediment recycling during preceding glaciations.