Jökull - 01.12.1982, Page 111

Shallow seismic Stratigraphy and Structure of the
southernmost Part of the Tjörnes Fracture Zone
KJARTAN THORS
Marine Research Institute, Skúlagata 4, 101 Reykjavík, Iceland
ABSTRACT
Sparker projiles show a steep contact between basaltic
basement and sediments parallel to gramty contours ojf the
coast between Gjögurtá and Flatey, northern Iceland. In
the bay oj Skjáljandajlói the basaltic basement rocks have
been modijied by glacial erosion. Modem sediments in the
bay are jaulted in response to movements in the Tjörnes
Fracture Zone.
INTRODUCTION
A steep gravity gradient oíTcentral northern Ice-
land described by Pálmason (1974) indicates a thick
accumulation of sediments in the southern part of
the Tjörnes Fracture Zone and a structural discont-
inuity between the crystalline rocks on land and
lighter rocks offshore. “Crystalline rocks”, in this
instance, refers to flexured tholeiitíc flood basalts
18°00 17°30 17°00
Fig. 1. Index map showing location of profiles. Heavy-lined part of profiles is illustrated in Figs. 2, 3 and
4. Free-air gravity contours after Pálmason (1974).
Mynd 2. Kort, sem synir meelingalínur á svteðinu jrá Gjögurtá að Tjömesi. Bókstajir auðkenna þœr línur, sem syndar
eru á 2., 3. og 4. mynd. Á kortið eru dregnar þyngdarlínur úr mtelingum Gubmundar Pálmasonar (1974).
JÖKULL 32. ÁR 107