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Type: Journal article
Title: Magnetic susceptibility of Middle Ordovician sedimentary rocks, Pakri Peninsula, NW Estonia
Author: Plado, J.
Ainsaar, L.
Dmitrijeva, M.
Põldsaar, K.
Ots, S.
Pesonen, L.
Preeden, U.
Citation: Estonian Journal of Earth Sciences, 2016; 65(3):125-137
Publisher: Estonian Academy Publishers
Issue Date: 2016
ISSN: 1736-4728
Statement of
Jüri Plado, Leho Ainsaar, Marija Dmitrijeva, Kairi Põldsaar, Siim Ots ,Lauri J. Pesonen and Ulla Preeden
Abstract: Magnetic susceptibility (MS), its frequency-dependence and anisotropy of the Middle Ordovician Dapingian and Darriwilian sedimentary sequence from three sites (Uuga, Testepere and Leetse) in the Pakri Peninsula, NW Estonia are analysed in combination with the mineralogical composition. The study is based on 463 cores drilled at intervals of a few centimetres to a maximum of about 1 m. All the samples show low and positive MS, which suggests the presence of small quantities of paraand/ or ferromagnetic minerals. The stratigraphic units of the three studied sites have a similar along-section appearance, which provides a base for a composite curve. The relatively higher susceptibilities are carried by secondary Fe–Ti oxides (Toila Formation), goethite ooids (Kandle Formation) and ferrous dolomite (Pae Member), whereas paramagnetic minerals are mostly responsible for the rest of the sequence. Considering the dependence of MS on regressive–transgressive cycles (high/low MS within deposits of regressive/transgressive parts of the cycles, respectively), the MS data do not agree with sedimentologically derived sea-level compilations. The measured changes in MS in the Pakri Peninsula outcrops correlate at certain characteristic levels with those deposited in the deeper part of the palaeobasin (Viki core), indicating that the post-depositional iron mobilization within the sediments took place at least at a regional level. Because of post-depositional reorganization of ferromagnetic carrier minerals, the MS values may, however, not be used as a detrital proxy.
Keywords: Magnetic susceptibility; carbonate rocks; Ordovician; Estonia
Rights: © 2016 Authors. This is an Open Access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International Licence (
DOI: 10.3176/earth.2016.11
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