Quaternary history of the Falkland Islands
Two episodes of Quaternary glaciation are recognised in the Falkland Islands; a marginal phase characterised by snowpatches and small glaciers terminating at threshold debris ridges (the 'Cirque' glaciation); and an earlier 'Valley Till' phase with glaciers up to 3km in length, terminating at ca 120-410m above sea level. During the 'Cirque' phase snow accumulated in favoured topographic locations under the influence of snowbearing winds with a resultant from due west; direct radiation had little impact upon glacier/snowpatch orientation. Precipitation was probably lower than at present, cloud cover at least as prevalent, and mean annual temperatures at least 2.4° - 3.2°C lower than the contemporary mean of 5.9°C. Broadly similar conditions probably prevailed during the 'Valley Till' phase, but with temperatures at least 3.0° - 3.7°C cooler than in the present-day. Unequivocal evidence for earlier and/or more widespread glaciation is lacking. Head deposits are widespread outside the glacial limits, and possibly derive from chemically rotted quartzite bedrock. At least six phases of mass wasting are recognised, but surface blockfields may be a late Quaternary phenomenon, contemporaneous with the 'Cirque' glaciation. The latter is bracketed between 27ka BP (a possible interstadial) and 6.5/5.9ka BP, though the glacial/postglacial boundary probably lies between l0ka and 9ka BP. 'Valley Till' glaciation probably predates 27ka BP. Two Holocene episodes of relatively higher sea level are postulated, together with three which predate at least one phase of periglacial slope activity. All raised marine levels are apparently horizontal, so that local glacio-isostatic effects are ruled out. Regional tectonic uplift is inferred during at least the Holocene period.