The East Siberian Sea is separated from the Laptev Sea on the west by the Kotel'nyy-Svatonos block uplift (zone of highs). Its boundary on the east with the Chukchi Sea is placed at Wrangel Island, which is at the western end of the Wrangel-Gerald ridge. To the north of Wrangel Island the boundary between the East Siberian and Chukchi Seas is drawn along the 180 degree meridian. The seas are not separated structurally.
Upper and lower structural stages are recognized. The upper consists of post-Neocomian Cretaceous and Cenozoic sediments. The base of this stage is most distinct where it rests on folded Mesozoic basement. The Novosibirsk, Blagoveshchen, and South Chukot downwarps and the eastern part of the Wilkins downwarp appear to have the most complete sections.
Seismic surveys in the Chukchi Sea to the east have disclosed three stratigraphic units. The first is probably Oligocene-Holocene and has velocities of 1.6-2.2 kmps. The second is correlated with the Cretaceous-Paleogene. Velocities are 2.4-3.5 kmps. The third is recognized only in the South Chukot downwarp. It has a velocity of 4.46 kmps and is separated from the second horizon by a 2.2 kmps layer. It rests on a Novo-Kimmerian basement with a velocity of 6.1 kmps. This third horizon appears to be Cretaceous (Aptian-Albian) molasse.
The borders of the downwarps and intervening highs are strongly faulted.
The lower structural stage consists of rocks of Late Proterozoic to Early Cretaceous age. Within it are Upper Jurassic-Lower Cretaceous, Upper Paleozoic-Middle Jurassic, and Upper Proterozoic-Middle Paleozoic sub-stages.
The Upper Jurassic-Lower Cretaceous sub-stage is recognized in the Novosibirsk and Blagoveshchen downwarps. Its base is correlated with magneto-active Horizon I. Maximum thickness exceeds 1 km in the southwest part of Novosibirsk downwarp. Rock varieties present are siltstone, argillite, clays, sandstone, and conglomerate. Folding is moderate, being stronger close to fold systems.
The Upper Paleozoic-Middle Jurassic sub-stage combines units of the Mesozoid geosynclinal deposits of the Novosibirsk and Chukot systems. Outside these fold zones these sediments are part of the sedimentary cover. Their thickness is not less than 3.5 km. The section consists of siltstone, argillite, and clays.
The Upper Proterozoic-Middle Paleozoic sub-stage includes sediments of the ancient platform cover on the De Long high and adjacent epi-Baykalian platform on the south. Maximum thickness exceeds 10 km. The age of sediments at the base of this sub-stage is different in various places. The oldest actually known rocks on De Long high are Middle Cambrian. On the east in the Wrangel Island region the oldest known sediments have a Late Silurian age. The most abundant rocks of this sub-stage are limestone, dolomite, siltstone, and argillite.
Taken from M. K. Kos'ko,1986, one trctonic map and one
cross section; digested in Petroleum Geology, Vol. 23, No. 5/6.
Copyright 2003 James Clarke. You are encouraged to print
out this News Letter and to forward it to others. Earlier News
Letters are available at: http://geocities.com/internetgeology
This News Letter is distributed without charge in the interest of
our science of petroleum geology. To be added to the mailing
list please send your e-mail address to: jamesclarke@erols.com
For information on the journal Petroleum Geology please telephone
703 759-4487 or FAX 703 759-3754. Vol. 37 for the year 2003
has been published, and I am well in to preparation of the material
for Vol. 38 for the year 2004. Please make provision through me or
your subscription agency for Vol. 38 so that I have a better idea as
to the size of this addition. The price is $89.00 per volume. Thank you.
Pleasant words are honeycomb, sweet to the soul and healing to
the bones. - Proverbs 16:24.