Paleomagnetic stratigraphy of younger basalts and intercalated plio-pleistocene tillites in Iceland

Abstract

This paper deals with the Plio-Pleistocene Graue Stufe in Eastern Iceland, which forms the upper part of the islands enormous pile of plateau basalts. A stratigraphy of the Graue Stufe has been established by using both paleomagnetic and petrographic criteria. Also the number and the stratigraphic position of the intercalated indurated moraines, the tillites, has been ascertained. The Graue Stufe embraces the N2, R1 and the lower part of the N1 paleomagnetic period. Petrographically the lava series contains tholeiites, porphyritic basalts and olivine basalts in a fairly irregular succession. Several tillites are intercalated in the lavas. The lowermost tillites are found in the middle part of the N2 series. As the N2 period is of pre-Quarternary age, glaciations in Iceland must have occurred already in the Pliocene. The results from Eastern Iceland have been compared with those of some other localities of the Graue Stufe in Iceland. The paleomagnetic stratigraphy is hampered by the occurrence of some flows, showing inverted remanent magnetization. Such inverted flows are locally found both in the N2 series and in the R1 series. This may be ascribed to extra, short periodical reversals of the geomagnetic field.