[meteorite-list] Ring Structures of North Caspian - Possible Impact Craters

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:01:32 2004
Message-ID: <200206111543.IAA00735_at_zagami.jpl.nasa.gov>

http://www.geocities.com/internetgeology/L145a.html

Ring Structures of North Caspian - Possible Hydrocarbon Reservoirs
Internet Geology News Letter No. 145, April 15, 2002

Seismic surveys in the Shortanbay area in the south of the North Caspian
depression have disclosed several ring structures, which are interpreted as
buried craters of possible meteorite impact origin. Many oil and gas fields
in the southeast part of Ural-Volga province are associated with ring
systems. The South Emba ring structure with diameter of 200 km is recognized
in the southeast of the North Caspian depression. Study of satellite images
along with geological and geophysical data has disclosed the gigantic Aral
ring, which has a diameter on the order of 700 km.

The ring structures of Shortanbay area show up in the pre- Kungurian section
of the Lower Permian at depths of 4.0-4.5 km beneath reflector P-1, the
first reflector below the Kungurian salt. One of these structures is west of
Kotlevskiy-Severnyy salt dome and has a diameter of about 3.5 km. Another
such structure is east of this dome; it is not as well expressed. Then to
the west of these is yet another possible structure. The morphology of these
structures is attributed to meteorite impact.

The structures described here are synchronous, occurring in the Lower
Permian section. Continental conditions were maximum in tne Permian for the
entire Paleozoic. Platforms almost everywhere became land areas. Salt was
deposited in broad internal seas (North Germany and Poland, Near-Urals,
North America, North Caspian). The largest catastrophic extinction of life
was at the boundary between the Permian and Triassic about 240 million years
ago. Only at the end of the Permian did life forms develop that extended
into the Mesozoic. The cause of this extreme situation remains unclear.

The traces of cosmic activity on the pre-Kungurian surface suggest that the
cause of this profound global change at the end of the Paleozoic may have
been intense meteorite bombardment during the first half of the Permian.
Geologic and climate changes following this bombardment led to deposition of
thick salt beds that covered the impact structures. This created ideal traps
for accumulation of hydrocarbons. The volume of the fracture pore space in
only one of the structures of Shortanbay area could hold about 250 million
tons of oil or 120 billion cubic meters of gas. Similar structures are known
in the Williston Basin, where three of the five known buried craters yield
commercial oil. It is quite possible that the proposed impact craters of the
south of the North Caspian depression are synchronous with those of the
Williston Basin.

The possibility for finding zones of impact crushing with good reservoir
properties in thde sub-salt section of the North Caspian depression along
with a reliable salt seal offers new prospects for this region.

Taken from Zeylik and Zozulin, 1995; digested in Petroleum Geology, vol. 31,
no. 4, 1997, two seismic sections.
Copyright 2002 James Clarke. You are encouraged to print out this News
Letter and to forward it to others.
Received on Tue 11 Jun 2002 11:43:36 AM PDT