PALEOENVIRONMENTAL STUDY BASED ON BENTHIC FORAMINIFERA IN GUETNA SECTION FROM TAFNA BASSIN, NW ALGERIA

Abstract

Our paleontological study examined a section from the Geutna region located in the Tafna basin Northwestern Algeria, dating back to the Neogene period (late Miocene). Our study aims to reconstruct the paleoenvironmental conditions that prevailed during the Tortonian stage, whose stratigraphic age was determined based on the presence of a key planktonic foraminifera species (Neogloboquadrina acostensis). Our research primarily relied on the distribution and evolution of benthic foraminifera, through which we identified14 species classified into 12 genera, most of which have calcareous test. This study distinguished two main environmental unit the first unit was dominated by the genus Ammonia; the second unit showed no dominant species (ecological equilibrium). We considered several factors, including foraminiferal assemblages, the number of benthic species, and the planktonic index, we were able to optian the following results, first stage a shallow marine environment with limited water exchange and minimal terrestrial sediment input. Second stage improved water circulation and increased terrestrial nutrient, enhancing the diversity of benthic and planktonic organisms. Third stage a return to marine esolution and reduced biodiversity. Fourth stage connection to the open sea without terrestrial sediment supply with rapid fluctuations possibly indicating influence, Considering the color variations in the layers (from gray to white to yellow), which reflect differences in depositional environments and rock/mineral composition over time, gray color: Indicates clay-rich rocks or organic limestone, formed in low-oxygen environments (e.g., deep oceans). White color: Suggests pure limestone, typically from clear marine environments or coral reef areas. Yellow color: Reflects iron oxides due to weathering or oxidation, signaling oxygen-rich environments (e.g., floodplains or continental regions). This color gradient represents a chronological sequence of the geological and climatic changes the region underwent during the formation of these layers.