EarthRef.org Digital Archive (ERDA) -- A new study of paleomagnetic directions in the Miocene lava pile...

Description
A new paleomagnetic study has been carried out on basaltic lava flows in the promontories between the fjords ArnarfjÃ¶rÃ°ur, TÃ¡lknafjÃ¶rÃ°ur, PatreksfjÃ¶rÃ°ur and BreiÃ°afjÃ¶rÃ°ur, VestfirÃ°ir peninsula of Northwest Iceland. This area is around 13 m.y. in age. The study involved mapping and sampling of 365 lava flows in 20 profile locations for laboratory measurement of magnetic remanence vectors; data from some 70 flows sampled previously were also available. A tentative scheme of paleomagnetic polarities is proposed for a composite section of 2.0 kilometers cumulative thickness, mostly overlapping with a stratigraphic column drawn up for the major part of the area by J. Preston in the early nineteen-seventies. At least six polarity reversals are encountered in the lava pile, as well as some apparent major excursions of the geomagnetic pole to middle and low latitudes. These are promising markers for stratigraphic correlation within and between the fjords, along with various lithologically distinctive units such as thick clastic sediments and cumulate plagioclase lavas. The rate of buildup of the lava pile is estimated to average 1.4 km/m.y. but it has been somewhat episodic, as nearidentical remanence directions are often recorded in two or more successive lavas. Additional work in the area is required before detailed correlations with previously mapped and sampled composite stratigraphic sections in the peninsula become feasible.