Re-sedimentation experiments with mud from the Southeastern Black Sea
Authors: Nowaczyk Norbert 
Published: March 2020

&lt;p align=&quot;justify&quot;&gt;&lt;span&gt;&lt;tt class=&quot;western&quot;&gt;M&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;agnetostratigraphic investigation &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;of &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;sediments &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;recovered &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;from the Southeastern Black Sea &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;yielded evidence for several geomagnetic excursions and, in association with these, a wide dynamic range in paleointensity variation. In order to check whether these low intensit&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;y&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt; &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;estimate&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;s are realistic, an intense re-sedimentation experiment is being performed. Up to now, most data published on re-sedimentation experiments cover only the intensity range of the present-day field, that is, from 20 to 70 &amp;#181;T, or even much higher. &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;T&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;he &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;new &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;deposition experiments &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;with Black Sea mud &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;a&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;re &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;being &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;performed &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;across almost 2 orders of magn&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;i&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;tude &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;from 1.8 to &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;11&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;4&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt; &amp;#181;T, with most data obtained with fields below &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;20 &amp;#181;T, &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;s&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;ince studied Black sea sediments, by comparison of obtained relative paleointensities to published absolute paleointensites, yielded fairly low field values &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;during excursions &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;of down to 3 &amp;#181;T. &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;For each field setting, over 3 to 4 days, a slurry with a density of 1.3 g/ccm was successively injected into 7 open sample boxes. Due to slowly drying and shrinking in air the slurry turned into pasty to stiff mud. In general, the &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;field &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;was &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;set&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt; anti-parallel to the ambient field,&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt; &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;using a coil cage for field control&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;. Acquired magnetizations were treated as natural samples with &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;determination of the anisotropy of magnetic susceptibility (AMS),&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt; stepwise alternating field demagnetization, normalization by anhysteretic remanent magnetizations (ARM) demagnetized the same way, &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;and IRM acquisition to check the mineralogical consistency of the Black Sea mud throughout time&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;. &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;A few experiments were performed with remanence acquisition in a field perpendicular to the ambient field with the coil field switched of after half a day and leaving the samples in the ambient field for further 2 days, or so, &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;for further compaction&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;. By this, it could be shown that the lock-in is very quick, since no field component parallel to the ambient field could be found &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;during&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt; demagnetization. &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;On a double-log diagram of acquired magnetization versus magnetic field, obtained &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;Black Sea mud &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;data plot align along a &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;straight &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;line, but with &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;a &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;slope lower than one, indicating a slightly non-linear behaviour with a slight underestimate of magnetic field towards higher fields (50 to 100 &amp;#181;T). &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;Nevertheless, &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;it can be concluded that Black Sea sediments &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;are fairly ideal recorders of &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;geomagnetic field behaviour &lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;providing valuable information about the geodynamo&lt;/tt&gt;&lt;tt class=&quot;western&quot;&gt;. &lt;/tt&gt;&lt;/span&gt;&lt;/p&gt;