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      Mid-Cretaceous paleoenvironmental changes in the western Tethys

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      Climate of the Past

      Copernicus GmbH

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          Abstract

          <p><strong>Abstract.</strong> We present a continuous record of surface water temperature and fertility variations through the latest Barremian–Cenomanian interval (ca. 27<span class="thinspace"></span>Myr) based on calcareous nannofossil abundances from the western Tethys. The nannofossil temperature index, calibrated with TEX<span class="inline-formula"><sub>86</sub></span> sea surface temperatures, suggests that warmest (34–36<span class="thinspace"></span><span class="inline-formula"><sup>∘</sup></span>C) conditions were reached during oceanic anoxic event (OAE) 1a onset, the Aptian–Albian boundary interval hyperthermals (113, Kilian level and Urbino level OAE 1b) and during a ca. 4<span class="thinspace"></span>Myr long phase in the middle Albian. Coolest temperatures (29<span class="thinspace"></span><span class="inline-formula"><sup>∘</sup></span>C) correspond instead to the late Aptian. Generally warm conditions characterized the Albian followed by a progressive cooling trend that started in the latest Albian (at the Marne a Fucoidi–Scaglia Bianca Formation transition). Temperate conditions occurred in the Cenomanian with frequent short-term variations highlighted by abundance peaks of the cold-water nannofossil species <i>E. floralis</i> and <i>R. parvidentatum</i>. Mid-Cretaceous surface water fertility was rather fluctuating and mostly independent from climatic conditions as well as from black shales intervals. Intense warming and fertility spikes were systematically associated only with black shales of OAE 1a and of the Aptian–Albian boundary hyperthermals. The Albian–Cenomanian rhythmic black shales are, in fact, associated with varying long-term climatic and fertility conditions. The similarity of western Tethys climatic and fertility fluctuations during OAE 1a, OAE 1b, the middle Albian and OAE 1d with nannofossil-based records from other basins indicated that these paleoenvironmental conditions were affecting the oceans at supra-regional to global scale.</p>

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          Most cited references 34

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          Geochemistry of oceanic anoxic events

           Hugh Jenkyns (2010)
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            Evolution of middle to Late Cretaceous oceans--A 55 m.y. record of Earth's temperature and carbon cycle

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              New oxygen isotope evidence for long-term Cretaceous climatic change in the Southern Hemisphere

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                Author and article information

                Journal
                Climate of the Past
                Clim. Past
                Copernicus GmbH
                1814-9332
                2018
                August 10 2018
                : 14
                : 8
                : 1147-1163
                Article
                10.5194/cp-14-1147-2018
                © 2018
                Product
                Self URI (article page): https://www.clim-past.net/14/1147/2018/

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