A surface of erosional planation, of regional extent in the central Canadian Arctic, was fragmented during the Eurekian Rifting Episode (Miocene-Pliocene) to produce the plateaus, plains, and lowlands of the study area and the rift valleys occupied by the large marine channels. Seven genetic groups of materials - rock, till, and glaciofluvial, glaciolacustrine, glaciomarine, marine, and fluvial sediments - constitute the surface of the map area, but rock and till are predominant. The till sheet exhibits major lateral facies changes which· define two large carbonate dispersal trains. Thick glaciomarine silt and clay extend in a wide belt across the southern part of the map area. Aspects of possible future engineering concern include: scarcity of sand and gravel in much of the area, natural instability of most unconsolidated material on slopes, high ground-ice content of thick till and fine grained glaciomarine sediment, annual thermal contraction and cracking of soil, frost heaving of soil and bedrock, ice push at sea and lake shores, and ice scouring of river beds and banks. Analyses of about 750 till samples provide the initial geochemical data base for this region. Variations in background levels of base metals reflect variations in carbonate content. All surface sediments shown on Map 1570A were deposited during the late Wisconsin glaciation. During the late Wisconsin maximum a major dome of the Laurentide Ice Sheet had a north-south oriented ice divide located over M'Clintock Channel. M'Clintock Dome was contiguous with the main body of the ice sheet to the south and coalesced with the Foxe Dome at the base of the Gulf of Boothia. M'Clintock Dome generated an eastward to east-northeastward flow over Boothia Peninsula and northern District of Keewatin. Important features of this flow regime were two large ice streams at the base of the ice sheet. Deglaciation began more than 9250 years ago and initial retreat was westward, towards the centre of the M'Clintock Dome. Retreat swung gradually to the south as a calving bay along the western side of Somerset Island and Boothia Peninsula penetrated the central parts of the dome. Boothia Peninsula was largely ice free by 8800 years B.P. and the marine-based part of the M'Clintock Dome had completely disappeared by 8700 years ago. A moraine system of regional extent in Arctic Canada, locally named the Chantrey Moraine System, was deposited shortly after 8700 years RP. and could reflect increased accumulation on the Laurentide Ice Sheet brought on by creation of a new moisture source when the sea invaded the region previously occupied by the northern part of the M'Clintock Dome. Emergence during deglaciation exceeded 30 m per century, at least in places, and averaged more than 53 cm per century during the last 4500 years.