Hecla Hoek Rocks of New Friesland (Spitsbergen)

Abstract

(I) In each of the areas examined the transition zone between the Hecla Hoek rocks of Eastern New Friesland and the more highly metamorphosed belt has been observed and the evidence points to a gradual increase in metamorphism westwards with the same general series of rocks involved. The rocks have been isoclinally folded and repetition occurs more especially on the east flank of the intensely metamorphosed zone. Usually only the Lower Murchison Bay Formation appears in the more highly folded belt, but it may well be that in the Stubendorff Mountains other rocks are also included.In the northern area, west of Treurenberg Bay, Blomstrand's recognition of a central core of granitic gneiss giving way on both sides to less highly metamorphosed types still stands as the most important contribution to the interpretation of the structure. Recent examination has revealed that the sequence of events has been a folding of the Lower Murchison Bay Formation followed shortly by igneous intrusion and metamorphism of the whole.In the Gullfaxe area isoclinally folded rocks of the Lower Murchison Bay Formation are associated with a quartz-felspargneiss. We have not been able to decide what this rock was originally. It may be either a metamorphosed igneous rock or an altered arkose. It appears to be concordant with the adjacent altered sedimentaries, but may be igneous material in some way related to the large granitic intrusion which lies farther west in this latitude.In the Lomme Bay area Odell observed the transition zone.(2) In the less altered zone to the east of the Duner Glacier we have been able to recognize the members of the Murchison Bay Formation as defined by Kulling, and the correlation is set out in Table I. The least satisfactory identification is of the Salodd and Raudstup Series. According to Kulling these Series have different characteristics in the Lomme Bay area from those which they show in North-East Land, and it may be that throughout New Friesland they attain neidier the thickness nor the distinctive character which is theirs in the type area. The presence of the other members of the Murchison Bay Formation and of the remarkable Sveanor Formation is well established.