Molluscan and sedimentological sequences of the late Quaternary deposits of Morsott region (NE Algeria) and their paleoenvironmental implication

Smaine Chellat,Ahcene Bourefis,Belhadj Hamdi-Aissa,Abderrezak Djerrab,Lotfi Toubal,Sihem Salmi-Laouar

doi:10.1051/bsgf/2018016

Abstract

The late Quaternary sequences of north-eastern Algeria composed of alternating dark and light layers, which are rich in molluscan fauna, could correspond to synchronous environmental phases. The facies variations of the Morsott Region deposits were systematically sampled as part of a sedimentological and malacological study in order to establish a palaeoenvironmental and climatic reconstruction of the late Quaternary. The alternation of sandy clayey silts levels, which contain abundant molluscan hygrophilous organisms, indicates an isostasis cycle followed, at the top, by a succession of rhexistasis and biostasis cycles. The molluscan record shows a dominant succession of xerophilous organisms in relation to the hygrophilous organisms. The faunistic richness in the fine levels is linked to sub-humid periods where the region has suffered numerous floods. The reduction in the number of species in the coarse levels comes is likely due to desiccation when the climate was semi-arid. This study is new in Algeria and will provide an insight into climatic changes. Further research will be required in order to understand the fluvial dynamics during the Quaternary.

Highlights

The molluscan and paleoenvironmental analyses of the Quaternary continental deposits from Morsott, NE Algeria, Africa (Fig. 1), have been limited compared to others areas, in North Africa, such as, the work carried out on recent Quaternary deposits in El Akarit wadi (Rognon et al, 1983), wadi Sbeitla in Tunisia (Zerai, 2006), and the Ksabi Basin (Middle Moulouya Basin) in Morocco (LimondinLozouet et al, 2012)
Set 1 was composed of sandy clayey silts, units C, F, H, J; the second lithological set grouped together the sandy silts,; levels E and K, the silty sands were grouped into set 3; while litological set 4, contained units D and L the breccias and pebbles (Tab. 1)
The molluscan study carried out on the Morsott deposits shows a succession of sandy clayey silts levels interspersed with sandy silts that record variations in sediment transportation regime

Summary

Introduction

The molluscan and paleoenvironmental analyses of the Quaternary continental deposits from Morsott, NE Algeria, Africa (Fig. 1), have been limited compared to others areas, in North Africa, such as, the work carried out on recent Quaternary deposits in El Akarit wadi (Rognon et al, 1983), wadi Sbeitla in Tunisia (Zerai, 2006), and the Ksabi Basin (Middle Moulouya Basin) in Morocco (LimondinLozouet et al, 2012). These deposits are of interest in stratigraphic, palaeoenvironment and Quaternary climate reconstitutions. Fluvio lacustrine deposits dated in Tunisia (Zerai, 2006), and in the south of Tebessa (Defaflia, 2013), gave an upper Pleistocene to Holocene age

Methods

Results

Discussion

Conclusion