Glaciations and High Sea-Level Phases, Black Island and Brown Peninsula.

Moraines and raised marine deposits were investigated on Black Island end Brown Peninsula. Weather and tine permitted a fairly thorough coverage of most of Black Island; the small ice-covered area at the south end of the island was not examined because the part was not sufficiently experienced in work in ice. A long spell of bad weather curtailed work on Brown Peninsula, and only about half of the peninsula was examined for moraines and marine deposits.

Marine deposits named Scallop Hill Formation, with fossils (Zygochlamys, barnacles and others) had been reported previously from Black Island and from morainic debris on sea ice near Brown Peninsula, but it was not known whether these deposits had been formed when the sec extended over parts of the present Black Island and Brown Peninsula, or had been dragged up from the sea by ice. These marine deposits were found by this year's expedition to have been deposited on a terrace-like feature ranging in elevation from about 550 to 700ft on both Black Island and Brown Peninsula. Another terrace-like feature at a loner level (200 to 400 ft) has marine deposits with different fossils (Adamussium colbecki). A third terrace-like feature, higher than the other two, appears to have no marine deposits on it. The marine deposits definitely represent periods when sea-level was higher than at present relative to Black Island end Brown Peninsula. It is not certain that the terrace-like features were formed by the sea, and they might be some kind of sub-aerial or glacial bench that has been flooded by the sea.

Almost nothing was previously known about the moraines of the region. Six distinct groups of moraines were mapped. Three groups represent thick ice-sheets, while the other three represent relatively minor and probably fairly recent phases of ice movement. The highest group of moraines extends up to an elevation of about 2,500 ft. and represents the oldest and thickest ice-sheet that has left a record in the area; it is composed mainly of basalt fragments up to about 4 inches in length and contains many erratic blocks of granite, Beacon Group sediments, dolerite, and c variety of metamorphic rocks, all evidently derived from the mainland on the west side of the Ross Sea, but it is uncertain whether they have been derived from the north-west, west or south-west, of Black Island and Brown Peninsula. The largest erratic blocks are granite and range up to 10 ft. in length. The surface of this oldest moraine is much subdued owing to periglacial action.

Younger moraines are mostly similar in composition, but one important group contains distinctive erratics of the lava kenyite and of concretionary fossiliferous marine sediments thought to be Tertiary in age, and also contains fragments of locally derived marine sediments containing the fossil Zygochlamys.

The sequence of 'terraces', marine formations, and moraines, appears to be as follows:

Direction of ice movement is not certain, hut from erratics, and from land forms probably shaped by ice, was probably mostly from north to south. Only the fifth grown in the above table, the 'trachyte' moraines of Black Island, shows evidence of ice movement from south to north. This group is probably late Holocene in age rid very young compared with the other moraines. The U.S. glaciologist Pewe has previously assumed ice-movement from south to north, but in order to account for the distribution of kenyite erratics has had to make the further assumption that kenyite outcrops extensively towards the head of the Koettlitz Glacier.

P. Vella.