The extent of impact induced fracturing from gravity modeling of the Granby and Tvaren simple craters
2010 (English)In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 485, no 1-4, 290-305 p.Article in journal (Refereed) Published
The Granby and Tvaren impact structures are two of the 5 recognized early Paleozoic impact structures in Scandinavia. They have a similar diameter of ca 2 km and contain a substantial post impact fill with Paleozoic sedimentary rocks. The Granby structure represents an almost completely preserved impact crater within a Paleozoic sedimentary rock sequence - only the uppermost part of the raised crater rim might be eroded and was subsequently covered by Quaternary sediments. The Tvaren structure is eroded below the surrounding pre-impact Paleozoic cover rocks into the underlying crystalline basement and has Quaternary sediment fill. Gravity measurements have been made on land, and in the case of the Tvaren structure also on sea ice, as a basis for modeling of the extent of impact induced fracturing below and around the craters, expressed as porosity. In the models, the contributions to the gravity field from the crater fill materials seawater, Quaternary sediments and Paleozoic sedimentary rocks are accounted for. The remaining negative gravity anomaly is related to the volume of impact fractured crystalline rock indicating an outward decreasing intensity of fracturing extending beyond the morphologic crater edge to ca 1.5 km radial distance from the explosion center. The remaining porosity in the central part of this sub-crater damage zone approaches 15%. A model is suggested for the gradual change of density and the equivalent porosity with radial distance within the damage zone around simple craters. (C) 2010 Elsevier B.V. All rights reserved.
Place, publisher, year, edition, pages
2010. Vol. 485, no 1-4, 290-305 p.
Impact crater, Gravity modeling, Impact fractured zone
IdentifiersURN: urn:nbn:se:kth:diva-27920DOI: 10.1016/j.tecto.2010.01.008ISI: 000277103300023ScopusID: 2-s2.0-77950546975OAI: oai:DiVA.org:kth-27920DiVA: diva2:382794
QC 201101032011-01-032011-01-032011-01-03Bibliographically approved