DIGITAL GEOLOGICAL MAPS USING MICROGRAFIX DESIGNER 4.0®: AN EXAMPLE FROM STEIGEN-ENGELØYA, NORTH-CENTRAL NORWAY

A computer generated 1:50,000 geological map of the Steigen-Engeløya area is presented.  Geological investigations in the area were conducted to address the following problems: (1) the relationship between two distinct Precambrian basement terranes in this region; (2) how nappe sequences evolved and were juxtaposed; and (3) what types of structures developed following amalgamation of the nappe stack. 

The structural position of the Lofoten basement relative to the Tysfjord basement remains speculative despite general agreement between workers that it is a western continuation of the Baltic shield and it had occupied a deep-crustal level during the Caledonian orogeny.  In Steigen-Engeløya, Lofoten basement lies directly above the Tysfjord basement and its associated cover.  Similar relations are known to occur further north on Hinnøya where the Austerfjord thrust separates the two terranes. 

The Bogøy and Jarstakkinden nappes of Steigen-Engeløya share many lithological, structural, and metamorphic similarities to the Bogen and Niingen nappes, respectively, of the Ofoten-Troms region.  This miogeoclinal sequence, therefore, is interpreted to continue southward across the Efjord-Tysfjord orogenic culmination and is a major component of the nappe stack at this latitude. 

Two episodes of extension were recognized in the study area, (1) a late-orogenic, tops-east ductile normal fault has down-dropped the structurally highest Jarstakkinden nappe into contact with the structurally low Lofoten basement, and (2) post-orogenic tops-west brittle extensional shears cross-cut the regional foliation in the Tysfjord basement.      

The computer generated map was developed in three stages: (1) the hand-drawn map was scanned as a jpeg file using an IDEAL FSC 8010, 85cm width, color scanner at Auburn University; (2) the scanned image was then imported into Micrografix Designer 4.0^â software and digitized using a Compaq^â Presario Notebook (333 Mhz and 92 MB RAM) and a Wacom^â pad and pen; and (3) the digitized map was exported as a windows metafile (wmf), imported into Corel^â Draw, and printed on an HP Designjet 2500 CP plotter at Auburn University.