Advanced

Combining shock barometry with numerical modeling : Insights into complex crater formation—The example of the Siljan impact structure (Sweden)

Holm-Alwmark, Sanna LU ; Rae, Auriol S.P.; Ferrière, Ludovic; Alwmark, Carl LU and Collins, Gareth S. (2017) In Meteoritics and Planetary Science 52(12). p.2521-2549
Abstract

Siljan, central Sweden, is the largest known impact structure in Europe. It was formed at about 380 Ma, in the late Devonian period. The structure has been heavily eroded to a level originally located underneath the crater floor, and to date, important questions about the original size and morphology of Siljan remain unanswered. Here we present the results of a shock barometry study of quartz-bearing surface and drill core samples combined with numerical modeling using iSALE. The investigated 13 bedrock granitoid samples show that the recorded shock pressure decreases with increasing depth from 15 to 20 GPa near the (present) surface, to 10–15 GPa at 600 m depth. A best-fit model that is consistent with observational constraints... (More)

Siljan, central Sweden, is the largest known impact structure in Europe. It was formed at about 380 Ma, in the late Devonian period. The structure has been heavily eroded to a level originally located underneath the crater floor, and to date, important questions about the original size and morphology of Siljan remain unanswered. Here we present the results of a shock barometry study of quartz-bearing surface and drill core samples combined with numerical modeling using iSALE. The investigated 13 bedrock granitoid samples show that the recorded shock pressure decreases with increasing depth from 15 to 20 GPa near the (present) surface, to 10–15 GPa at 600 m depth. A best-fit model that is consistent with observational constraints relating to the present size of the structure, the location of the downfaulted sediments, and the observed surface and vertical shock barometry profiles is presented. The best-fit model results in a final crater (rim-to-rim) diameter of ~65 km. According to our simulations, the original Siljan impact structure would have been a peak-ring crater. Siljan was formed in a mixed target of Paleozoic sedimentary rocks overlaying crystalline basement. Our modeling suggests that, at the time of impact, the sedimentary sequence was approximately 3 km thick. Since then, there has been around 4 km of erosion of the structure.

(Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Meteoritics and Planetary Science
volume
52
issue
12
pages
29 pages
publisher
Wiley-Blackwell
external identifiers
  • scopus:85036586148
  • wos:000416937300005
ISSN
1086-9379
DOI
10.1111/maps.12955
language
English
LU publication?
yes
id
af348c20-710f-4c8d-9428-6658d505a8a6
date added to LUP
2017-12-18 09:19:43
date last changed
2018-01-28 04:34:38
@article{af348c20-710f-4c8d-9428-6658d505a8a6,
  abstract     = {<p>Siljan, central Sweden, is the largest known impact structure in Europe. It was formed at about 380 Ma, in the late Devonian period. The structure has been heavily eroded to a level originally located underneath the crater floor, and to date, important questions about the original size and morphology of Siljan remain unanswered. Here we present the results of a shock barometry study of quartz-bearing surface and drill core samples combined with numerical modeling using iSALE. The investigated 13 bedrock granitoid samples show that the recorded shock pressure decreases with increasing depth from 15 to 20 GPa near the (present) surface, to 10–15 GPa at 600 m depth. A best-fit model that is consistent with observational constraints relating to the present size of the structure, the location of the downfaulted sediments, and the observed surface and vertical shock barometry profiles is presented. The best-fit model results in a final crater (rim-to-rim) diameter of ~65 km. According to our simulations, the original Siljan impact structure would have been a peak-ring crater. Siljan was formed in a mixed target of Paleozoic sedimentary rocks overlaying crystalline basement. Our modeling suggests that, at the time of impact, the sedimentary sequence was approximately 3 km thick. Since then, there has been around 4 km of erosion of the structure.</p>},
  author       = {Holm-Alwmark, Sanna and Rae, Auriol S.P. and Ferrière, Ludovic and Alwmark, Carl and Collins, Gareth S.},
  issn         = {1086-9379},
  language     = {eng},
  month        = {12},
  number       = {12},
  pages        = {2521--2549},
  publisher    = {Wiley-Blackwell},
  series       = {Meteoritics and Planetary Science},
  title        = {Combining shock barometry with numerical modeling : Insights into complex crater formation—The example of the Siljan impact structure (Sweden)},
  url          = {http://dx.doi.org/10.1111/maps.12955},
  volume       = {52},
  year         = {2017},
}