title: New results on the hydrodynamic behaviour of fossil Nummulites tests from two nummulite banks from the Bartonian and Priabonian of northern Italy.
abstract: Settling velocities of 58 well-preserved tests of fossil Nummulites were experimentally determined using a settling tube. The tests were collected from the nummulite banks of Pederiva di Grancona (A forms of N. lyelliandN. striatus, Middle Eocene) and San Germano dei Berici (A and B forms of N. fabianii, Late Eocene), both in the Berici Mts. (Veneto, northern Italy). The data were compared with estimated settling velocities that the same specimens might have had in life conditions. This was done by reconstructing their densities simulating water-filled condition and, to simulate post-diagenetic effects, under calcite-filled condition. These simulations show that A and B forms, even if they greatly diverge in shape, volume and size, still possess comparable settling velocities, and that each nummulite bank is characterized by specific hydrodynamic parameters. The use of settling velocity as a parameter to quantify the hydrodynamic behaviour of particles in seawater enables estimation of palaeoenvironmental conditions such as depth, substrate and the energy scenario. Such information is useful in obtaining further insights into the genesis of nummulite banks, the autochthony or allochthony of which is still being debated. Our results point to an autochthonous interpretation.
authors.affiliation: Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 103, I-41125 Modena, Italy; mona66310@gmail.com.
authors.forename: Mona
authors.initials: M
authors.lastname: Seddighi
authors.affiliation: Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, Gadong BE1410, Brunei Darussalam; antonino.briguglio@ubd.edu.bn.
authors.forename: Antonino
authors.initials: A
authors.lastname: Briguglio
authors.affiliation: Institut für Paläontologie, Universität Wien, Geozentrum, Althanstrasse 14, A-1090 Wien, Austria; johann.hohenegger@univie.ac.at.
authors.forename: Johann
authors.initials: J
authors.lastname: Hohenegger
authors.affiliation: Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 103, I-41125 Modena, Italy.
authors.forename: Cesare Andrea
authors.initials: CA
authors.lastname: Papazzoni
keywords: Eocene; Larger Foraminifera; Settling velocity; nummulite banks; taphonomy; test density