Holocene sedimentary environment of Cambridge Fiord, Baffin Island, Northwest Territories

Abstract

The Holocene sedimentary environment of Cambridge Fiord in northeastern Baffin Island is interpreted from six piston cores. Distinct sediment types represent three sedimentary processes. (1) Muds deposited from suspension from fluvial sources at the fiord head and glacial sources near the mouth are the dominant components of the sediments. The rate of accumulation in mid-fiord based on a radiocarbon date on dispersed organic material indicates an average rate of sedimentation of 1.24 mm/a since about 5800 BP. Upper portions of the cores are bioturbated, although bands of well-preserved fine rhythmites indicate the sudden loss of the benthos, perhaps caused by oxygen depletion associated with reduced circulation. Rhythmites near the sediment surface have a mean thickness similar to the calculated annual accumulation, indicating that they probably are varves; those at depth average 8.1 mm thick. Fine sediment at depth in several cores was not bioturbated for long periods, indicating reduced effectiveness of the benthos during periods of higher rates of sedimentation. Graded muds and sandy muds are interpreted as deposits from weak underflows generated in the sediments on the fiord walls. (2) Massive sands deposited near the head of the fiord are the result of cohesionless debris flows from sources of fluvial and littoral sand widely distributed along the fiord floor. (3) Single sand- and pebble-sized particles found everywhere in the muds are interpreted as ice-rafted debris.

Glacial-Marine Sedimentation, Canadian Polar Margin, North of Axel Heiberg Island

“…Where bioturbation occurs, it reaches 'downsection' from a depositional disconformity, which indicates intervals of rapid deposition (or deposition under anoxic conditions) stopped burrowing activity, which resumed when environmental stressors were reduced {Cf. Andrews and Jennings, 1987;Gilbert et al, 1990). Detailed textural analysis of this faciès suggests that most of the lamination arises from fine-grained turbidity currents, alternating with suspension fall-out (Hein et al, 1990).…”

Geomagnetic secular variations (inclination) of high latitude fiord cores: eastern Canadian Arctic

“…2) (cf. Gilbert et al 1990;Eyles et al 1987). Such sediments reflect deposition in quiet water where conditions should, theoretically, be suitable for the acquisition of a stable, post-depositional remanent magnetization (PDRM) (Verosub 1977).…”

“…Sand-size particles have been contributed from ice rafting and eolian transport (cf. Gilbert et al 1990). The uppermost unit in the fiords is acoustically transparent; it represents reworking of the glacial marine sediments and focused deposition of suspended sediment.…”

“…In most cores there is evidence of ice-rafting and sediment gravity flows (cf. Andrews et al 1986;Gilbert et al 1990) (Fig. 21, both of which have the potential for imprinting a strong depositional remanent magnetic (DRM) signature.…”

“…1; Table 1); hence inclinations should be slightly steeper. The single 14-C date of 3.5 ka (Table 2) suggests that the sedimentation rate has been c. 1 m/ka, or about twice the late Holocene rates in cores TI3, IT2.3, MC4.1, and MC7 (see also Gilbert et al 1990). A rate of 1 m/ka was used to produce Fig.…”