Topographical and geological maps of Hall Land, North Greenland. Description of a computer- supported photogrammetrical research programme for production of new maps, and the Lower Palaeozoic and surficial geology

Abstract

Topographical and geological map sheets covering the northern part of Hall Land (81-82°N) are presented – an area of about 3000 km². The maps are the products of a research programme in which newly developed photogrammetric techniques have been used in the interpretation and compilation of the topography and the geology (both solid and surficial). The topographical map has been constructed with a minimum of geodetic ground control. The topographic contours have been calculated from a digital elevation model using computer programmes, and automatically plotted out. The geological map has been hand-drawn from 74 manuscript sheets compiled from aerial photograph models on second-order analog stereo-plotting instruments with computer facilities. The maps, the photogrammetric programme and the solid and surficial geology are described in seven chapters. The first two provide an introductory background that explains the motivation for the research, summarises the history of cartographic, geodetic and geologic work and provides a status of research at the start of the programme. The third chapter discusses the various aspects of the photogrammetric programme, instrumentation and the on-line computer facilities utilised, and is followed by a chapter dealing with compilation method, map presentation and assessment of cartographic accuracy compared to previous maps and modern geodetic ground data. The next chapter describes the topography and geomorphology and relates the three main physiographic provinces to the solid and surficial geology. The penultimate chapter outlines the stratigraphy and structure of the Upper Ordovician-Silurian (Llandovery-Pridoli) section through the E-W trending Franklinian basin. In Ordovician-earliest Silurian time, the map area was part of the carbonate platform; in the Llandovery a major shift southwards of the deep-water basin occurred. The Silurian succession displays a regional facies change from platform carbonates in the south, through a major reef belt on the shelf and upper slope to, in the north, clastic turbidites of the lower slope and trough. Facies transitions and interdigitation of shelf-slope-trough lithologies are complex. The northern part of the map exposes the autochthonous margin of the mid-Palaeozoic North Greenland fold belt characterised by E-W folds. The regional structure is an asymmetric synclinorium; a decollement zone probably occurs in the shale sequence that overlies the Lower Silurian carbonate platform. The final chapter describes eight groups of Quaternary deposits and features: moraine, fluviatile-glaciofluvial, marine, lacustrine, colluvial, solifluction, aeolian and periglacial. Hall Land was formerly entirely ice covered, and deposits of several ice advances are preserved; six major marginal moraine systems are defined. Marine deposits are prominent and terrace levels and raised shorelines are well preserved; the Holocene marine limit is at least 125 m above present sea level. Major events are placed within a Pleistocene-Holocene chronostratigraphic framework. Comments on place names are given in an appendix.