Tiny, glassy, and rapidly trapped: The nano-sized planktic diatoms in Messinian (late Miocene) gypsum

Abstract

Primary gypsum represents an excellent paleobiological archive due to its early and fast growth, favoring the preservation of delicate biomineralized structures. The Mediterranean region is renowned for evaporite deposits that formed during the Messinian salinity crisis (MSC), an event that supposedly annihilated most of the marine biota. However, the Messinian evaporites have been scarcely studied for their fossil content. Abundant nano-sized planktic diatoms and associated organic matter are observed for the first time in bottom-grown gypsum crystals that formed during the early stage of the MSC in different marginal basins of the western Mediterranean. This discovery increases our knowledge of the Messinian biota and reveals that nano-sized planktic diatoms played a prominent role in carbon and silicon export during gypsum deposition. The co-occurrence of these diatoms with larger diatoms, possibly associated with a deep chlorophyll maximum, suggests that Messinian gypsum formed in stratified and relatively deep basins (far below the photic zone), typified by marine conditions in the upper water column. The nano-sized planktic diatoms may have taken advantage of the hydrological reconfigurations experienced by the Mediterranean since the onset of the MSC. This study confirms that primary gypsum represents a promising archive of information for elucidating the marine biotic response to an ancient environmental crisis.

Effect of Different Evaporation Rates on Gypsum Habit: Mineralogical Implications for Natural Gypsum Deposits

“…Notwithstanding, 100 and 01 penetration twins have never been identified in the sedimentary successions deposited in response to these dramatic modifications of the basin hydrologic balance. These complex chemical environments rich in organic and inorganic compounds deriving, for instance, from both planktonic and benthonic biological activity − may have selected different twinning laws of gypsum with respect to the 100 and 01 penetration ones. However, crystal growth experiments claim that specific organic molecules commonly found in sedimentary environments (tannic acid, deriving from the decomposition of plant leaves; α-amylase, an enzyme excreted into soils and water by bacteria, fungi, algae, and plant roots) promote the formation of 100 and 01 penetration twinning laws. , Therefore, there is apparently no valid reason that 100 and 01 penetration twins cannot be observed in modern and ancient sedimentary successions.…”

A Messinian Gypsum Deposit in the Ionian Forearc Basin (Benestare, Calabria, Southern Italy): Origin and Paleoenvironmental Indications

“…The presence of traces of ancient microbial life in different salt-saturated environments (shallow and deep) may provide information about salinity, depth of the basins, light penetration, oxygen and nutrient availability. Recent studies described a diversified and well-preserved body and molecular fossil assemblage within Messinian selenites, confirming that gypsum evaporites represent an excellent archive of microbial life [6,30,31].…”

From biogenic silica and organic matter to authigenic clays and dolomite: Insights from Messinian (upper Miocene) sediments of the Northern Mediterranean

“…However, the scattered presence of biosiliceous fossils in the MSC sedimentary record (e.g. Fourtanier et al ., 1991; Carnevale et al ., 2019; Meilijson et al ., 2019; Pellegrino et al ., 2021) suggests that biosiliceous biota persisted during the MSC. Such an interpretation is consistent with the late Miocene to early Pliocene ‘biogenic bloom’ event and the associated dramatic intensification of deposition of biogenic silica centred between 7.0 Ma and 4.5 Ma (e.g.…”

“…Petrographic and organic geochemical data (Table 4) suggest that marine productivity dominated by planktonic diatoms, generating organic matter and biogenic silica, persisted during the early stage of the MSC (cf. Fourtanier et al ., 1991; Pellegrino et al ., 2021). The well‐preserved diatom valves in the diatomaceous shales (Fig.…”