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[1] The interpretation of tectonic and sedimentary structures in the northern Chukchi region, Arctic Ocean, is important to enhance our understanding of the tectonic evolution of this region. Therefore, multichannel seismic lines as well as seismic wide-angle reflection and refraction data were acquired in the northern Chukchi region during the RV Polarstern ARK-XXIII/3 summer expedition in 2008. These data have been processed and interpreted for the three main geological provinces (Chukchi Plateau, Chukchi Abyssal Plain, and Mendeleev Ridge) to describe the sedimentary and basement structures of the northern Chukchi region. Furthermore, using the age control of five exploration wells drilled near the coast of Alaska in combination with additional seismic reflection lines located on the Chukchi Shelf, we were able to date sediment horizons within the research area. In total, six sediment horizons with ages between Barremian/Hauterivian and the Top Miocene were identified. Especially, the Top Oligocene horizon forms a pronounce unconformity on the Chukchi Plateau and on the Mendeleev Ridge flanks. The origin of this unconformity can be associated with the opening of the Fram Strait indicating a significant change in the Arctic Ocean current system.

[1] Relative sea level (RSL) variations are a result of tectonic activity, changing of the water volume in ocean basins (e.g. due to increasing/decreasing of ice volume, evaporation) and variations in regional to global climate, which influence erosional processes and material transport. We present multi-channel seismic data combined with dated sediment horizons from the Chukchi Shelf, Arctic Ocean. Based on a series of prograding sequences in the upper 4 km of sediments and the method of seismic sequence stratigraphy, we introduce the first RSL curve for the Chukchi region, beginning in the late Eocene (40 Ma). The comparison of the Chukchi RSL curve with the global RSL curve shows that RSL lowering events in the Chukchi region do not correlate with global events for the Eocene/ Oligocene -early Miocene. Between the Eocene/Oligocene and the late Oligocene, the Chukchi RSL variations were small (< 100 m). Since the late Oligocene the Chukchi RSL increased until the opening of the Fram Strait in the early Miocene. We show that the Chukchi RSL variations are representative for the Arctic Ocean, and conclude that the Arctic Ocean was an isolated basin for the Eocene/ Oligocene -early Miocene. Citation: Hegewald, A., and W.Jokat (2013), Relative sea level variations in the Chukchi regionArctic Ocean -since the late Eocene, Geophys. Res. Lett., 40,[803][804][805][806][807]

[1] Gravity records include a wide spectrum of signals based on mass changes in the Earth's crust. Today, the detectable amplitudes of the signals of interest become smaller and smaller (e.g., hydrological effects). From this it follows that the accuracy and resolution of measurements must be very high and the noise level as low as possible. In this study, the influence of the temperature variations as noise signal in the gravity records was investigated. Therefore, two 215 day time series of the LaCoste and Romberg gravity meter ET18 in the broadband Geodynamical Observatory Moxa were analyzed and compared. Each time series was recorded in another room. The first room is characterized by a temperature variation of ±4°C per year. The second room has a constant temperature of 19°C. As reference data, the parallel recorded time series of the superconducting gravity meter (SG) CD-034, installed in the temperature-stabilized room were used. The result of this study shows a clear influence of temperature variation on the noise level in the spectra of the ET18 compared to the SG spectra. Depending on the frequency ranges, the ratios of the noise levels of the ET18 and SG spectra are between 2 and 5. In the frequency range up to 0.01 cph the ET18/SG factor is 2, between 0.01 cph and 0.09 cph the factor is 3, and above 0.09 cph the factor is 5.

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