Paper No. 90-6
Presentation Time: 9:00 AM-5:30 PM
PALAEOZOIC & MESOZOIC TECTONIC EVOLUTION OF NOVAYA ZEMLYA: FROM GEOCHRONOLOGICAL AND THERMOCHRONOLOGICAL EVIDENCE
The Novaya Zemlya archipelago lies on the eastern Barents Sea Shelf and formed near the junction of the paleocontinents of Baltica and Siberia. It is a predominantly NW-verging, early Mesozoic fold-and-thrust belt that exposes Precambrian to early Triassic successions. To better understand the sediment provenance and exhumation history of Novaya Zemlya’s fold and thrust belt, we apply detrital zircon U-Pb geochronology combined with zircon and apatite fission track (FT) analyses to samples from the Precambrian to late Permian siliciclastic successions. The detrital zircon age spectra of all samples contain 2.0 - 0.9 Ga and 700 - 490 Ma zircons in varying proportions. From early Devonian to late Devonian, the 2.0 - 0.9 Ga ages decrease dramatically, whereas the 700 - 490 Ma ages become dominant. Zircons of 336 - 302 Ma ages appear in the early Permian sample and the early Permian sample. Very few zircons of 470 - 420 Ma exist in the early Devonian sample. Zircon FT ages for individual units are older than their stratigraphic ages and consistent with single age population distributions. The ZFT results document no annealing after deposition and therefore preserve provenance information that indicates the source rock(s) of each sample most likely experienced the same thermal event. Integration of these data indicates that Sveconorwegian sources could be eroded, transported and deposited in the Barents Shelf, and then remobilized to Novaya Zemlya during Caledonian orogenesis. Late Carboniferous to early Permian cooling ages from the Neoproterozoic to Cambrian samples may suggest greater proximity to the Uralides or a far-field effect of the Uralian orogenesis to southeastern Novaya Zemlya. Apatite FT ages and thermal modeling identify a rapid cooling event at 220 – 210 Ma, consistent with late Triassic deformation on Novaya Zemlya.