The potential of high-resolution stable isotope records in the bivalve Angulus benedeni benedeni's shells to investigate Pliocene seasonality
Authors: Wichern Nina , de Winter Niels , Ziegler Martin , Johnson Andrew , Hamers Maartje , Goolaerts Stijn 
Published: March 2022

&lt;p&gt;Obtaining temperature data from the mid-Piacenzian warm period (mPWP) is a key factor in understanding the coming changes brought upon by anthropogenic climate change. The mPWP, a high-CO&lt;sub&gt;2&lt;/sub&gt; world with a paleogeography similar to modern times, has been used to validate and improve model retrodictions, which in turn enables assessing the prediction strength of these models&lt;sup&gt;1&lt;/sup&gt;. For the first time, stable isotope analysis has been applied to the extinct tellinid bivalve &lt;em&gt;Angulus benedeni benedeni&lt;/em&gt;, originating from the mid-Piacenzian of the Lillo Formation of Belgium in the southern North Sea basin. Multi-annual oxygen isotope records with a seasonal resolution obtained from its shell indicate that this species could live for up to a decade and formed monthly growth increments. From this oxygen isotope record, a clumped-isotope-based mean annual temperature of 12.6 &amp;#177; 3.6&amp;#176;C was reconstructed. This is 2.1&amp;#176;C warmer than today&lt;sup&gt;2,3&lt;/sup&gt;, 2.6&amp;#176;C warmer than the pre-industrial North Sea&lt;sup&gt;2&lt;/sup&gt;, and in line with global Pliocene temperature estimates of +2-4&amp;#176;C compared to the pre-industrial climate&lt;sup&gt;4,5&lt;/sup&gt;. The pristine nature of the aragonitic shell material was verified through electron backscatter diffraction analysis (EBSD), and backed up by light microscopy, X-ray diffraction, and X-ray fluorescence. The various microstructures as obtained from the EBSD maps have been described, and they provide a template of pristine &lt;em&gt;A. benedeni benedeni&lt;/em&gt; material to which potentially altered shells may be compared. The bivalve &lt;em&gt;A. benedeni benedeni&lt;/em&gt; is suitable for high resolution isotope-based paleoclimatic reconstruction and it can be used to unravel the marine conditions in the Pliocene North Sea basin at a seasonal scale, yielding enhanced insight into imminent western European climate conditions.&lt;/p&gt;&lt;ul&gt;&lt;li&gt;&lt;sup&gt;1&lt;/sup&gt;Dowsett, H. J. &lt;em&gt;et al.&lt;/em&gt; Assessing con&amp;#64257;dence in Pliocene sea surface temperatures to evaluate predictive models. &lt;em&gt;Nature Climate Change&lt;/em&gt; &lt;strong&gt;2&lt;/strong&gt;, 365&amp;#8211;371 (2012). https://doi.org/10.1038/NCLIMATE1455&lt;/li&gt;
&lt;li&gt;&lt;sup&gt;2&lt;/sup&gt;Emeis, K.-C. &lt;em&gt;et al.&lt;/em&gt; The North Sea &amp;#8212; A shelf sea in the Anthropocene. &lt;em&gt;Journal of Marine Systems&lt;/em&gt; &lt;strong&gt;141&lt;/strong&gt;, 18&amp;#8211;33 (2015). https://doi.org/10.1016/j.jmarsys.2014.03.012&lt;/li&gt;
&lt;li&gt;&lt;sup&gt;3&lt;/sup&gt;Locarnini, R. A. &lt;em&gt;et al.&lt;/em&gt; World Ocean Atlas 2018, Volume 1: Temperature. &lt;em&gt;NOAA Atlas NESDIS 81. &lt;/em&gt;A. Mishonov, Technical Editor. 52pp. (2019). https://www.ncei.noaa.gov/access/world-ocean-atlas-2018/&lt;/li&gt;
&lt;li&gt;&lt;sup&gt;4&lt;/sup&gt;Dowsett, H. J. &lt;em&gt;et al.&lt;/em&gt; Sea surface temperature of the mid-Piacenzian ocean: a data-model comparison. &lt;em&gt;Scientific reports&lt;/em&gt; &lt;strong&gt;3&lt;/strong&gt;, 1&amp;#8211;8 (2013). https://doi.org/10.1038/srep02013&lt;/li&gt;
&lt;li&gt;&lt;sup&gt;5&lt;/sup&gt;Haywood, A. M. &lt;em&gt;et al.&lt;/em&gt; The Pliocene Model Intercomparison Project Phase 2: large-scale climate features and climate sensitivity. &lt;em&gt;Clim. Past&lt;/em&gt; &lt;strong&gt;16&lt;/strong&gt;, 2095&amp;#8211;2123 (2020). https://doi.org/10.5194/cp-16-2095-2020&lt;/li&gt;
&lt;/ul&gt;