A palaeomagnetic study and age determinations have been performed on Ediacaran basalts from the northwestern Ukraine. Whole-rock 40 Ar/ 39 Ar age determination revealed plateau ages at 590–560 Ma and 393 Ma, the latter probably reflecting a resetting of the radiometric system. Palaeomagnetic poles have been calculated from five basalt flows, two of which (A poles) are considered reliable with ages that range from 580 to 560 Ma. Tentative poles (B poles), calculated from most probably primary magnetizations, have ages estimated at 580–545 Ma. Secondary magnetizations, possibly of late Ediacaran or Devonian age, have also been isolated (C poles). Based on the new poles, Baltica drifted together with Laurentia from an equatorial position at c . 750 Ma to occupy high southern latitude positions at c . 580 Ma. Baltica during that time period was joined to Laurentia in a similar relative position to that at 750 Ma. The two shields then split up from each other and from c . 550 Ma Baltica drifted at moderately high latitudes and rotated some 180° during the final opening of the Iapetus ocean. This reconstruction suggests that during the Ediacaran glaciation Baltica occupied high-latitude positions, which contradicts the high-obliquity model to explain low-latitude Neoproterozoic glaciations.

No abstract

No abstract

We report on a palaeomagnetic study from Mesozoic sedimentary and volcanic rocks from the conjugate areas of the Western Black Sea Basin; that is, the Crimean Peninsula in the north and the Western and Central Pontides in the south, to better constrain their palaeogeographic relationships within the southern margin of Eurasia.From the study of 87 sites in Crimea, we found that Triassic to Lower Jurassic sandstones and siltstones from the Tavric series, and Middle-Upper Jurassic sandstones, siltstones and limestones exhibit remagnetization. Both fold and conglomerate tests confirm a widespread remagnetization in Crimea. Comparison of palaeopoles with the expected reference apparent polar wander path (APWP) of Eurasia and results from conglomerate tests suggest that the remagnetization occurred in the Early Cretaceous. In the Central Pontides, no reliable palaeomagnetic results can be obtained from Triassic-Upper Jurassic rocks, however, a negative fold test in Upper Jurassic-Lower Cretaceous rocks from the Western Pontides shows that the palaeolatitude agrees with Lower Cretaceous data from Crimea. Our new palaeomagnetic results indicate a pervasive remagnetization in Crimea and the Western Pontides that could be attributed to the rifting phase of the Black Sea Basin during Lower Cretaceous.

No abstract