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Shock barometry of the Siljan impact structure, Sweden

Alwmark, Sanna LU ; Alwmark, Carl LU ; Alvarez, Walter and Schmitz, Birger LU (2011) In Meteoritics and Planetary Science 46(12). p.1888-1909
Abstract
The Siljan impact structure in Sweden is the largest confirmed impact structure in Western Europe. Despite this, the structure has been poorly studied in the past, and detailed studies of shock metamorphic features in the target lithologies are missing. Here, we present the results of a detailed systematic search for shock metamorphic features in quartz grains from 73 sampled localities at Siljan. At 21 localities from an area approximately 20 km in diameter located centrally in the structure, the orientations of 2851 planar deformation feature sets in 1179 quartz grains were measured. Observations of shatter cones outside of the zone with shocked quartz extend the total shocked area to approximately 30 km in diameter. The most strongly... (More)
The Siljan impact structure in Sweden is the largest confirmed impact structure in Western Europe. Despite this, the structure has been poorly studied in the past, and detailed studies of shock metamorphic features in the target lithologies are missing. Here, we present the results of a detailed systematic search for shock metamorphic features in quartz grains from 73 sampled localities at Siljan. At 21 localities from an area approximately 20 km in diameter located centrally in the structure, the orientations of 2851 planar deformation feature sets in 1179 quartz grains were measured. Observations of shatter cones outside of the zone with shocked quartz extend the total shocked area to approximately 30 km in diameter. The most strongly shocked samples, recording pressures of up to 20 GPa, occur at the very central part of the structure, and locally in these samples, higher pressures causing melting conditions in the affected rocks were reached. Pressures recorded in the studied samples decrease outwards from the center of the structure, forming roughly circular envelopes around the proposed shock center. Based on the distribution pattern of shocked quartz at Siljan, the original transient cavity can be estimated at approximately 3238 km in diameter. After correcting for erosion, we conclude that the original rim to rim diameter of the Siljan crater was somewhere in the size range 5090 km. (Less)
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Meteoritics and Planetary Science
volume
46
issue
12
pages
1888 - 1909
publisher
Wiley-Blackwell
external identifiers
  • wos:000298094600008
  • scopus:83055176291
ISSN
1086-9379
DOI
10.1111/j.1945-5100.2011.01303.x
language
English
LU publication?
yes
id
498fa51a-4811-4ef1-a784-11fc9ad2270d (old id 2306990)
date added to LUP
2012-02-07 10:54:36
date last changed
2017-07-23 04:03:27
@article{498fa51a-4811-4ef1-a784-11fc9ad2270d,
  abstract     = {The Siljan impact structure in Sweden is the largest confirmed impact structure in Western Europe. Despite this, the structure has been poorly studied in the past, and detailed studies of shock metamorphic features in the target lithologies are missing. Here, we present the results of a detailed systematic search for shock metamorphic features in quartz grains from 73 sampled localities at Siljan. At 21 localities from an area approximately 20 km in diameter located centrally in the structure, the orientations of 2851 planar deformation feature sets in 1179 quartz grains were measured. Observations of shatter cones outside of the zone with shocked quartz extend the total shocked area to approximately 30 km in diameter. The most strongly shocked samples, recording pressures of up to 20 GPa, occur at the very central part of the structure, and locally in these samples, higher pressures causing melting conditions in the affected rocks were reached. Pressures recorded in the studied samples decrease outwards from the center of the structure, forming roughly circular envelopes around the proposed shock center. Based on the distribution pattern of shocked quartz at Siljan, the original transient cavity can be estimated at approximately 3238 km in diameter. After correcting for erosion, we conclude that the original rim to rim diameter of the Siljan crater was somewhere in the size range 5090 km.},
  author       = {Alwmark, Sanna and Alwmark, Carl and Alvarez, Walter and Schmitz, Birger},
  issn         = {1086-9379},
  language     = {eng},
  number       = {12},
  pages        = {1888--1909},
  publisher    = {Wiley-Blackwell},
  series       = {Meteoritics and Planetary Science},
  title        = {Shock barometry of the Siljan impact structure, Sweden},
  url          = {http://dx.doi.org/10.1111/j.1945-5100.2011.01303.x},
  volume       = {46},
  year         = {2011},
}