The Yenisey-Khatanga regional downwarp is a narrow eastward extention of the northeast part of the West Siberian basin. It separates the Taymyr system of east-west dislocations on its north from the Siberian craton on its south. It is filled by a 7-12 km thickness of Mesozoic clastics. The North Siberian monocline is disposed along the north flank of the Siberian craton.
Even at an early stage of study the gravity anomalies indicated a group of large arches that extend east-northeast more than 1000 km from the left-bank area of the Yenisey River to Kiryano-Tass arch of the Taymyr. These arches are disposed diagonally within the downwarp. From west to east they are the Malokhet, Rassokhin, and Balakhnin.
Recent common depth point seismic surveys have yielded more accurate information on the deep subsurface of these arches and their effect on Mesozoic sedimentation in the adjacent depressions. Late Jurassic-Neocomian deformation and significant pre-late Valanginian erosion are of particular interest. At the crests of the arches Cretaceous sediments are either absent completely or are substantially reduced in thickness.
Westernmost Malokhet arch extends west-southwest across the Yenisey River and for 150-200 km into the left-bank area. The axis of this feature experiences significant undulation and plunges to the west.. Several local highs in the left-bank area are oil-gas-bearing. Sukhodin high in the right-bank area is not productive. Messoyakha, Yuzhno-Solenin, and Severo-Solenin fields have been discovered on the flanks of this arch.
On the Cretaceous sediments Malokhet arch has the form of a large box fold with some bifurcation of the axis on the west. The north part of the west nose rotates to the northwest, and the south part plunges steeply to the southwest. Geophysical anomalies indicate that this arch has a steep frontal boundary on the west with deep north-south-trending structures. The crest of the arch is cut into blocks by assumed east-west and diagonal faults and is bounded on the north and south by regional flexure-fault zones.
Along the Yenisey River the north flank of Malokhet arch has a relatively calm tectonic face, flattening out to the north. Deformation of the Cretaceous, Jurassic, and Triassic rocks is similar and conformable. The south flank of Malokhet arch exhibits change along trend. On the west in the zone of junction with Dolgan downwarp it is a steep near-vertical fault with displacement on the Jurassic rocks of up to 1000 m. In this zone there is a clearly expressed structural discordance at the boundary between the Jurassic and Triassic. Then to the east the displacement on the south flank of Malokhet arch decreases.
Modern sediments occur in a depression at the site of Malokhet arch, indicating recent inversion. Continued.
Taken from Baldin, K. N. Kunin, and N. Ya. Kunin, 1997;
digested in Petroleum Geology, vol. 31, no. 4, 1997,
three cross sections.
Copyright 2002 James Clarke. You are encouraged to print out
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