Spatial heterogeneity of the Late Miocene Biogenic Bloom

Abstract

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

A Global Reassessment of the Spatial and Temporal Expression of the Late Miocene Biogenic Bloom

“…A table with the following information for each data set is available in Table S1 and on SEANOE (Pillot, 2023): site number, data set label, site label, publication, elevation, site coordinates, site paleocoordinates (10 Ma), available variables, variables used for labeling, the time scale used in the original publication, and the web link to the original data set.…”

“…However, because of the reevaluation of age-depth models, all data sets as used in this study have been deposited on SEANOE (Pillot, 2023). The metadata and the original citations are available for each data set in Table S1 and on SEANOE (Pillot, 2023). The time series of all variables in all data sets are also available in this repository.…”

“…All data used in this study have been previously published. However, because of the reevaluation of age-depth models, all data sets as used in this study have been deposited on SEANOE (Pillot, 2023). The metadata and the original citations are available for each data set in Table S1 and on SEANOE (Pillot, 2023).…”