Spatial heterogeneity of the Late Miocene Biogenic Bloom
Authors: Pillot Quentin , Suchéras-Marx Baptiste , Sarr Anta-Clarisse , Bolton Clara , Ladant Jean-Baptiste , Donnadieu Yannick 
Published: March 2022

&lt;p&gt;&lt;span&gt;The late Miocene and early Pliocene is marked by a major&lt;/span&gt;&lt;br&gt;&lt;span&gt;oceanographic and geological event called the Late Miocene Biogenic&lt;/span&gt;&lt;br&gt;&lt;span&gt;Bloom (LMBB). This event is characterized by high accumulation rates of&lt;/span&gt;&lt;br&gt;&lt;span&gt;opals from diatoms and high calcite accumulation rates from calcareous&lt;/span&gt;&lt;br&gt;&lt;span&gt;nannofossils and planktic foraminifera. The LMBB extends over several&lt;/span&gt;&lt;br&gt;&lt;span&gt;million years and is present in the Pacific, Atlantic and Indian Oceans. Two&lt;/span&gt;&lt;br&gt;&lt;span&gt;hypotheses have emerged from the literature to explain this event: a&lt;/span&gt;&lt;br&gt;&lt;span&gt;global increase in the supply of nutrients to ocean basins through chemical&lt;/span&gt;&lt;br&gt;&lt;span&gt;alteration of the continents and/or a major redistribution of nutrients in the&lt;/span&gt;&lt;br&gt;&lt;span&gt;oceans. The objective of this study is to provide a more comprehensive&lt;/span&gt;&lt;br&gt;&lt;span&gt;look at the temporal and geographical aspects of the LMBB. We have&lt;/span&gt;&lt;br&gt;&lt;span&gt;compiled ocean drilling data (ODP-IODP) covering the late Miocene and&lt;/span&gt;&lt;br&gt;&lt;span&gt;early Pliocene. This compilation contains sedimentation rates as well as&lt;/span&gt;&lt;br&gt;&lt;span&gt;CaCO&lt;/span&gt;&lt;span&gt;3&lt;/span&gt;&lt;span&gt;, opal and terrigenous accumulation rates. After a careful screening&lt;/span&gt;&lt;br&gt;&lt;span&gt;of the database, checking that all data are on the same time scale, we first&lt;/span&gt;&lt;br&gt;&lt;span&gt;work on global trends of sedimentation and biogenic production before&lt;/span&gt;&lt;br&gt;&lt;span&gt;going into more details. For instance, we show that the magnitude of the&lt;/span&gt;&lt;br&gt;&lt;span&gt;Biogenic Bloom strongly varied between the three oceanic basins.&lt;/span&gt;&lt;br&gt;&lt;span&gt;Normalization to a post-LMBB state allows comparison of rates of increase&lt;/span&gt;&lt;br&gt;&lt;span&gt;in CaCO&lt;/span&gt;&lt;span&gt;3&lt;/span&gt;&lt;span&gt; accumulation in different geographical areas (grouping several&lt;/span&gt;&lt;br&gt;&lt;span&gt;sites). A very strong LMBB signature is present in oceanic area bordering&lt;/span&gt;&lt;br&gt;&lt;span&gt;the western side of Australia. In the Atlantic Ocean, it is mainly present&lt;/span&gt;&lt;br&gt;&lt;span&gt;near the equator and over South Africa. The LMBB signature is less&lt;/span&gt;&lt;br&gt;&lt;span&gt;pronounced in the Indian Ocean but remains trackable near the northern&lt;/span&gt;&lt;br&gt;&lt;span&gt;coasts of the basin. Moreover, it is also heterogeneous in terms of the&lt;/span&gt;&lt;br&gt;&lt;span&gt;mineralogy produced and deposited in the deep ocean between regions.&lt;/span&gt;&lt;br&gt;&lt;span&gt;For example, in the equatorial eastern Pacific, the LMBB signature is&lt;/span&gt;&lt;br&gt;&lt;span&gt;present in the silica accumulation term but not in carbonates accumulation&lt;/span&gt;&lt;br&gt;&lt;span&gt;one. Outputs from coupled ocean/atmosphere models (IPSL-CM5A2) using&lt;/span&gt;&lt;br&gt;&lt;span&gt;late Miocene paleogeography and integrating a marine biogeochemistry&lt;/span&gt;&lt;br&gt;&lt;span&gt;module (PISCES) have been gathered and will be discussed in regard to&lt;/span&gt;&lt;br&gt;&lt;span&gt;our database.&lt;/span&gt;&lt;/p&gt;