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   Results of the study of structure of sedimentary basins
   in the Eastern Asia Arctic zone
   based on decompensative gravity anomalies

The data was obtained as a result of the study of structure of sedimentary basins in the Eastern Asia Arctic zone is analysed by employing the approach based on decompensative gravity anomalies.


Figure 1.Topography and bathymetry of the study area.
Dark grey contours represent positions of sedimentary basins.
The basin captions are in bold.
The dashed line indicates continental boundaries of the Okhotsk-Chukotka volcanogenic belt (OCVB).
Here and in all subsequent maps the following abbreviations are used to denote the sedimentary basins:
L-MB Laptev-Moma basin,
ZB Zyryanka basin,   PrB Primorsk basin,
TB Tastakh basin,     ChB Chauna basin,
PeB Penzhin basin,   PB Pustorets basin, AB Anadyr basin.

The sedimentary thickness and density models, differing in their initial conditions, have been obtained. They demonstrate essentially new details on the structure, shape and density of the sedimentary basins compared to geological studies [Koporulin, 1979; Clarke, 1988; Morozov, 2001; Petrov, 2016 et al.].
First, we computed the isostatic gravity anomalies for the study area, and then we applied the decompensative correction to the isostatic anomalies. The correction spans within a range of 50 to +30 mGal and principally changes the isostatic anomaly patterns. Thus, new details have been obtained, compared to the initial sedimentary model displayed on Figure 2b and compiled from results by [Straume et al., 2019; Stolk et al., 2013; Kaban, 2001].
The main discoveries are as follows:

1. Essential changes in the sedimentary thickness and the depocenter location have been found for the Anadyr basin in its continental part, where the thickness has been reduced to 12 km comparing to previous surveys.

2. New details of the sedimentary thickness variations have been revealed for the central part of the Penzhin basin, where the thickness appeared to be lower by about two times comparing to the initial model, and for the Pustorets basin, for which the new location of the depocenter has been identified.

3. For the offshore part of the Chauna basin (referred as the Ayon basin), the sedimentary thickness has appeared to be 2-2.5 km in the new model, which is lower than in the initial model (4 km). The new result agrees with the marine seismic surveys, which confirms robustness of the method.

4. The most significant lateral redistribution of the sedimentary thickness has been found for Lower Cretaceous coal-bearing strata in the northern part of the Zyryanka basin. The new model indicates the connection of two coal-bearing zones, revealing the features of the Lower Cretaceous strata that were not previously mapped due to insufficient geological surveys.

5. New details on the sedimentary thickness variations have been discovered for the Primorsk basin. The sedimentary thickness in the basin is significantly reduced in the southeast direction.

The overall analysis of two new models confirms the efficiency of the approach based on the decompensative gravity anomalies. This approach application has made it possible to reveal several essential changes in the geological structure of the analysed sedimentary basins. In many cases, the results of our study are the only ones providing the information on the structure of sedimentary basins in the studied region.

The dataset includes the data grids obtained as a result of the analysis of structure of sedimentary basins in the Eastern Asia Arctic zone by employing the approach based on decompensative gravity anomalies. The data are freely accessible.

The study area spans from 135° to 190°E and 65° to 74°N;
the initial area was larger and included the 5600x5400 km in the orthographic projection
with a center point 162.5°E, 72.5°N. This was done for more convenient calculation.

Data and grids in zip archives have the following designations:





Figure 2. a - Initial Bouguer gravity data. b - Initial sedimentary thickness model





Figure 3. a - Isostatic correction. b - Isostatic gravity anomalies





Figure 4. a - Decompensative correction. b - Decompensative gravity anomalies





Figure 5. New sedimentary thickness models. a - Model 1. b - Model 2





Figure 6. a - Sedimentary density correction. b - Sedimentary density model


This work was funded by the Russian Science Foundation (project No. 21-77-30010).

The results are presented in the article:

Roman V. Sidorov, Mikhail K. Kaban, Anatoly A. Soloviev, Alexei G. Petrunin, Alexei D. Gvishiani, Alexei A. Oshchenko, Anton B. Popov, and Roman I. Krasnoperov.
Sedimentary basins of the eastern Asia Arctic zone: new details on their structure revealed by decompensative gravity anomalies.
Solid Earth, 12, 27732788, 2021. https://doi.org/10.5194/se-12-2773-2021


References

    Koporulin, V. I. Accumulation conditions and lithogenesis of the Lower Cretaceous deposits of the Zyryanka basin, Geological Institute of the USSR Academy of Sciences: Transactions, Vol. 338, Moscow: Nauka. 181 p. (in Russian), 1979.

    Clarke J. W. Sedimentary basins of Northeastern USSR, US Department of the Interior, Geological Survey, URL: https://pubs.usgs.gov/of/1988/0264/report.pdf (accessed on 18.04.2021), 1988.

    Morozov, O. L. Geological structure and tectonic evolution of Central Chukotka, Geological Institute of the Russian Academy of Sciences: Transactions, Vol. 523, Moscow: GEOS, 208 p. (in Russian), 2001.

    Petrov, O., Shokalsky, S., Kashubin, S., Sobolev, N., Petrov, E., Sergeev, S., Morozov, A., Artemieva, I. M., Ernst, R. E., Smelror, M.: Crustal structure and tectonic model of the Arctic region, Earth Sci. Rev., 2016. Vol. 154. P. 29-71.

    Straume, E. O., Gaina, C., Medvedev, S., Hochmuth, K., Gohl, K., Whittaker, J. M., Fattah, R. A., Doornenbal, J. C., Hopper, J. R.: GlobSed: Updated total sediment thickness in the world's oceans, Geochem. Geophy. Geosy., 20, 1756-1772, https://doi.org/10.1029/2018GC008115, 2019.

    Stolk, W., Kaban, M. K., Beekman, F., Tesauro, M., Mooney, W. D., Cloetingh, S.: High resolution regional crustal models from irregularly distributed data: Application to Asia and adjacent areas, Tectonophysics, 602, 5568, https://doi.org/10.1016/j.tecto.2013.01.022, 2013.

    Kaban, M. A Gravity Model of the North Eurasia Crust and Upper Mantle: 1. Mantle and Isostatic Residual Gravity Anomalies, Russian Journal of Earth Sciences, 3, https://doi.org/10.2205/2001ES000062, 125-144, 2001.

    Förste, C., Bruinsma, S. L., Abrikosov, O., Lemoine, J.-M., Marty, J. C., Flechtner, F., Balmino, G., Barthelmes, F., Biancale, R.: EIGEN-6C4 The latest combined global gravity field model including GOCE data up to degree and order 2190 of GFZ Potsdam and GRGS Toulouse, GFZ Data Services: Potsdam, Germany, https://doi.org/10.5880/icgem.2015.1, 2014.

URL:   http://www.wdcb.ru/arctic_antarctic/arctic_grav_1.html

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