Late Holocene Glacier Fluctuations and Vegetation Changes at Maktak Fiord, Baffin Island, N.W.T., Canada

Abstract

Maktak Glacier is a major distributary of the Penny Ice Cap and thus changes in its frontal position reflect variations in the mass balance of the ice cap. The Neoglacial terminal moraine of this glacier consists of a 20-m thick sedimentary sequence of till, overlain by up to 18 m of sands and gravels which contain a 1-m thick peat bed. These sediments were deformed by glacier pushing and are overlain by a younger till. The basal till and the overlying sands and gravels beneath the peat were deposited during the retreat from the Cockburn Stade. The site was deglaciated at some time after 5000-6000 BP. Peat on a terrace surface was studied using absolute pollen analyses, and clustering routines to distinguish pollen zones. The start of peat growth at 2500 BP (synchronous with such events elsewhere) is attributable to altered permafrost levels and/or increases in precipitation/evaporation budgets, producing wetter conditions locally. The vegetational history began with a moist willow episode, which was followed by a dominantly grass community as local conditions became drier. The initial rapid growth of peak became progressively slower throughout the profile, until by 1500 BP the slow accumulation of humified peat was overwhelmed by windblown sand which inhibited further growth. A subsequent Maktak Glacier advance deposited sands and gravels over the peat bed. Between 350-65 BP, glacial pushing and overriding of the terrace and peat sediments occurred. Exotic tree pollens were identified in the sediments; their changing frequencies may provide some tentative measure of changing airflows into the High Arctic. The eastern part of the Penny Ice Cap, as represented by the Maktak Glacier, may have a relatively simple Holocene history of post-Cockburn decline, growth after 4000 BP and decline in recent decades. This contrasts with more complex response patterns of small cirque glaciers in the same areas. It is stressed that the data used in the paper cannot identify small-scale glacier oscillations.