(a) Cape Barne

The ice-free area adjacent to this Cape is situated 33 kms NNW of Scott Base. Cape Barne forms a right angle in the coastline. Along the southern side are three partially dissected basalt cones, the most westerly exposed to the interior where two dykes and associated agglomerates have resisted marine erosion to form the Cape Barne Pillar. To the north, kenyte lavas have flowed westwards from sources high on Mt. Erebus. During Pleistocene times ice is considered to have cut two parallel arcuate valleys, concave to the west, within the kenytes, each about 100 ft. deep. These valleys now possess three lakes, and adjacent to them are steep cliffs which display a complex of polygonal joints radiating outwards from the centres of the kenyte lava flows. To the east, most of the bedrock outcrops are mantled with moraine, forming a hummocky topography with many distinctive debris cones.

Within the inner eastern valley a small pass of moraine separates two of the lakes. It is at this site, within and upon the surface of the moraine, that the fossils have been located. Consisting of three beds, alongside a prominent mirabilite deposit, the fossils consist mostly of molluscs, bryozoans, sponge spicules and foraminifera.

The kenyte forms an undulating topography with bedrock cropping out on the higher levels to form small tors which display well developed polygonal jointing. Within the hollows coarse sands have accumulated which are considered to represent the end product of salt weathering out the individual crystals within the bedrock to form 'lag gravels'. A thin morainic cover may be located in a few places which often contains diagnostic pale green kenyte erratics.

The moraine to the east extends northwards to form the coastline of Backdoor Bay and southwards to the Barne Glacier. Kenyte erratics are to be found on the basalt cones to the south, whilst two moraine mounds a little to the north are composed almost entirely of basalt with a few granite erratics. On steeper slopes only the coarse angular blocks remain as a scree, the fines presumably winnowed away by the wind. In contrast, the gentle lower slopes form more typical morainic lithologies of unsorted, chaotic masses of blocks, sands and silts which frequently form solifluction deposits.

Marine sands and gravels have accumulated at the seaward ends of the outer, western coastal valley. Here four raised beaches were levelled for height and distance from sea level.

The basalt cones to the south have been denuded to expose central dykes and breccias with interdigitating steeply dipping lava flows. A curved fault plane was discovered within the eastern cone, which is considered to represent a fault of similar structure to a cone-sheet dyke. Considerable controversy surrounds the age relationships between the basalts and kenytes. Smith (1954) draws no conclusions, whilst Treves (1962) considered the basalts were older. Our field observations were not conclusive, but there is a strong suggestion that kenyte overlies basalt at one locality. Between the two eastern basalt cones is a low saddle with an outcrop of kenyte bedrock, which we consider must be younger than the basalt. Furthermore, no basalt scoria or lavas were found upon the kenyte lavas.

Thus from our work the geological history of Cape Barne could be summarised into the following series of events:

(a)	Eruption of basalt cones;
(b)	Outpouring from flanks of Erebus of kenyte lava flows (at least three successive flows are visible near Cape page 16 Royds.
(c)	The cutting of the two arcuate valleys by an enlarged ice sheet, which occupied McMurdo Sound, with erosion of the seaward portions of the basalt cones.
(d)	The deposition of moraines over extensive areas of land behind the cape, less than 32,000 years ago.
(e)	The deposition of beach gravels and sands at both ends of the seaward valley prior to the postglacial rise in sea level. This is assumed because the present lake within the valley is beneath present day sea level, and there is no indication of a former, larger lake which has decreased in size to its present form.

Detailed petrological and geochemical examination of the rock types is proceeding at present, together with identification of fossil molluscs and bryozoans collected from within the inner valley, and also at two localities within moraine along the coast of Backdoor Bay.