Tecronophysics, 116 (1985) 63-93 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands 63 zyxwvutsrqpo TECTONIC ANALYSIS OF LINEAMENTS NEAR A SPREADING AXIS, NORTHEASTERN ICELAND NED MAMULA’ and BARRY VGIGHT * ’ Center for zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Tectonophysics, Texas A&M University, College of Geosciences, College Station, TX 77843 (U.S.A.) ’ Department of Geosciences, The Pennsylvania State University, College of Earth and Mineral Resources, University Park, PA I6802 (U.S.A.) (Received by publisher December 19, 1984) ABSTRACT Mamula, N. and Voight, B., 1985. Tectonic analysis of iineaments near a spreading axis, northeastern Iceland. In: G.F. Sharman and J. Francheteau (Editors), Oceanic Lithosphere. Tecto~aphysjcs, 116: 63-93. Some aspects of Iceland geodynamics are investigated from Landsat multispectral scanner (MSS) digital data in conjunction with field studies. Lineaments at the 1: 500,000 scale were mapped from computer processed imagery designed to enhance subtle structural fabric elements within the data. The analyses indicate pervasive north and west-nor~west-tren~ng lineaments. These trends are interpreted in terms of alternative complex models involving Riedel shear deformation or thermoelastic contraction adjacent to a spreading center. West-northwest-trending lineaments are concentrated along the Husavik-Flatey fault system. East of Axarfjordur, a 20-km wide band of west-northwest lineaments could mark the onshore continuation of the Grimsey submarine fault proposed on the basis of earthquake distributions. INTRODUCTION As the largest well-exposed landmass along an actively spreading mid-ocean ridge system, Iceland cannot be understood without also looking at the su~ounding seafloor. Conversely, much can be learned about the oceans by studying Iceland because its exposure is more conducive for many kinds of observations (Jacoby et al., 1980). Even so, the linkage of Iceland to plate tectonic theory remains enigmatic. This stems, in part, from the incompletely resolved relationship of active rifts to oceanic fracture zones and tr~sfo~ faults in the vicinity of Iceland. Though evidence for Icelandic fracture zones has been reported (Sykes, 1967; Tryggvason, 1968, 1973; Ward et al., 1969; Ward, 1971; Schafer, 1972; Saemunds- son, 1974; Trifonov, 1978; Einarsson, 1979; and Sigurdsson, 1980, structures in- ~1951/85/$03.30 0 1985 Elsevier Science Publishers B.V.