Messinian paleoenvironmental evolution in the lower Guadalquivir Basin (SW Spain) based on benthic foraminifera

Abstract

Benthic foraminiferal assemblages of a drill core from the lower Guadalquivir Basin (northern Gulf of Cádiz, SW Spain) have been analysed in order to reconstruct the paleoenvironmental evolution in the vicinity of the Betic seaways during the Messinian. The core consists of marine sediments ranging from the latest Tortonian to the early Pliocene. Changes in the abundance of certain marker species, planktonic/benthic ratio (P/B ratio), paleodepth estimated with a transfer function, content of sand grains and presence of glauconitic layers indicate a complete transgressive-regressive sea-level cycle from the bottom to the top of the section. An abrupt sea-level rise, from inner-middle shelf to middle slope, is recorded at the lowermost part of the core (latest Tortonian-earliest Messinian), followed by a relatively rapid shallowing from middle slope to outer shelf. Magnetobiostratigraphic data show These assemblages are dominated by Nonion fabum and Bulimina elongata, two taxa that are able to feed from continental low-quality organic matter, most likely derived from river run-off. The paleoenviromental evolution on the Atlantic side of Betic and Rifian seaways is similar during the Messinian, with a Messinian continuous sea-level lowering driven by regional tectonic uplift and upwelling-related waters reaching the upper slope. This study will further contribute to understand the role of tectonics on the sea-level changes as well as on the closure of the Atlantic-Mediterranean gateways that led to the MSC, and on the paleoceanography on the Atlantic sides of these corridors.

The effect of bioturbation by polychaetes (Opheliidae) on benthic foraminiferal assemblages and test preservation

“…Furthermore, upwelling events affected nearly coeval outer‐shelf and upper‐slope deposits along the north‐western margin of the Guadalquivir Basin (Pérez‐Asensio et al . , ). Although upwelling does not have an episodic nature, cyclic influence of upwelling conditions might have occurred due to changes in the direction or intensity of prevailing winds, inducing upwelling in the study area.…”

Observing the past to better understand thefuture: a synthesis of the Neogene climate inEurope and its perspectives on present climatechange

“…Upwelling phenomena occurred in the Guadalquivir basin, strongly fed by organic matter from rivers [117]. Environmental data from small mammal palaeoecology suggests open-herbaceous habitats and warm temperatures in the Iberian Peninsula, with air temperatures between 2.5 ∘ C to 4.7 ∘ C higher than today, and summer humidity between 60 to 70% [118].…”

“…In the Tortonian-Messinian transition, the more or less stable conditions of the first half of the Upper Miocene started to disappear [104]. The Messinian came to be divided into 3 stages: 1) Pre-evaporitic ( tonic elevation of the Betic-Rif Mountain chain closed the connection between the Mediterranean and the North Atlantic [111,113,115,117]. The evaporation in the Mediterranean Sea lead to a great drop in sea level, leading to the development of a land connection between the European continent and the Balearic, Corsica and Sardinia islands.…”

Imprint of Messinian Salinity Crisis events on the Spanish Atlantic margin

“…The Montemayor-1 borehole has been drilled in this part of the basin (Fig. 1) and several paleoenvironmental studies using pollen data, stable isotopes, environmental magnetism, benthic foraminifera and XRF data have been carried out (Pérez-Asensio et al 2012b, 2012a, Larrasoaña et al 2014). These studies demonstrate important cooling events, astronomically induced climate change and continuous infilling of the basin from east to west.…”