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Geophysical signature of Malingen, the minor crater of the Lockne-Malingen doublet impact structure

Journal article
Authors I. Melero-Asensio
J. Ormo
Erik Sturkell
G. Stockmann
J. Mansfeld
Published in Meteoritics & Planetary Science
Volume 53
Issue 7
Pages 1456-1475
ISSN 1086-9379
Publication year 2018
Published at Department of Earth Sciences
Pages 1456-1475
Language en
Links dx.doi.org/10.1111/maps.13090
Keywords central sweden, swedish caledonides, terrestrial impact, hiiumaa island, marine, gravity, environment, jamtland, density, estonia, Geochemistry & Geophysics
Subject categories Earth and Related Environmental Sciences

Abstract

Malingen is the 0.7km wide minor crater associated to the 10 times larger Lockne crater in the unique Lockne-Malingen doublet. The craters formed at 458Ma by the impact of a binary asteroid related to the well-known 470Ma Main Belt breakup event responsible for a large number of Ordovician craters and fossil meteorites. The binary asteroid struck a target sequence including similar to 500m of sea water, similar to 80m of limestone, similar to 30m of dark mud, and a peneplainized Precambrian crystalline basement. Although the Lockne crater has been extensively studied by core drillings and geophysics, little is known about the subsurface morphology of Malingen. We performed magnetic susceptibility and remanence, as well as density, measurements combined with gravity, and magnetic field surveys over the crater and its close vicinity as a base for forward magnetic and gravity modeling. The interior of the crater shows a general magnetic low of 90-100nT broken by a clustered set of high-amplitude, short wavelength anomalies caused by bodies of mafic rock in the target below the crater and as allogenic blocks in the crater infill. The gravity shows a general -1.4mgal anomaly over the crater caused by low-density breccia infill and fractured crystalline rocks below the crater floor. The modeling also revealed a slightly asymmetrical shape of the crater that together with the irregular ejecta distribution supports an oblique impact from the east, which is consistent with the direction of impact suggested for the Lockne crater.

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