Baltica during the Ediacaran and Cambrian: A paleomagnetic study of Hailuoto sediments in Finland

Abstract

We present a new Late Neoproterozoic paleomagnetic pole for Baltica from an inclined 272m deep oriented sedimentary drill core in Hailuoto, Western Finland. The depositional age of the Hailuoto sediments is poorly constrained at 570–600 Ma. Three components of magnetization were isolated with thermal and alternating field (AF) demagnetization treatments. The ChRM (characteristic remanence magnetization) component is a high coercivity/unblocking temperature dual polarity component that passes a reversal test. The combined observed ChRM component of the Hailuoto sediments (D=334.2°; I=44.4°; α95=7.2°; k=16.5) yields a paleomagnetic pole of Plat=48.7°N and Plon=241.1°E with A95=8.1°. The inclination corrected direction (f=0.6) of D=334.4°; I=57.7°; α95=5.8°; k=25.2 yields a paleomagnetic pole of Plat=60.5°N and Plon=247.9°E with A95=7.6°. As it is a dual-polarity ChRM carried by both magnetite and hematite, with no resemblance to younger events, we interpret it as a primary component. A paleolatitude for Hailuoto of 38.3° was calculated from the ChRM. Two secondary components were identified. The first is a low coercivity/blocking temperature component with a remanent magnetization of D=239.0°; I=67.3°; α95=8.7° (N=13 samples), which we interpret as drilling-induced remanent magnetization (DIRM). The second secondary component has a remanent magnetization of D=49.4°; I=34.9°; α95=8.6° (N=5 samples) and is commonly seen in Fennoscandian formations.The ChRM Hailuoto pole adds to the scattered Ediacaran paleomagnetic data of Baltica and indicate large distances between other late Neoproterozoic and early Cambrian paleomagnetic poles. We present reconstructions of Baltica and Laurentia between 616 and 550 Ma which move Baltica from high latitudes (615 Ma), over the polar region, to low latitudes (550 Ma), and Laurentia from low latitudes (615 Ma) to a polar position (570 Ma) and back to an equatorial position (550 Ma). A low to mid latitude position of Baltica determined by the Hailuoto paleomagnetic pole, and the lack of glaciogenic sediments determined in an earlier study of Hailuoto sediments indicate a warm deposition environment.