An exploratory Early and Middle Holocene sedimentary record with palynoforms and diatoms from Faiyum lake, Egypt

摘要

We report on the sedimentology, pollen and diatom records in a 26 m long core of Holocene sediments from the Tersa area, near the centre of the Faiyum Depression (Egypt). Two radiocarbon and one OSL dates have been obtained for the core, dates range from 9545 +/- 60 Cal. BP to c. 4040 BP. These correspond respectively with the Terminal Palaeolithic (Qarunian) and Neolithic Faiyum A (Faiyumian) cultures. The core is subdivided into 3 sedimentological units: unit 1 (21-26 m) is very thinly laminated, calcareous silt deposited in a deep water lake; unit 2 (9.5-21 m) is finely laminated sand, silt and carbonates formed as a lacustrine fan delta; unit 3 (9.5 m to the core top), is formed of massive silt, sandy silt and very fine grained flood plain sands. Planktonic diatom taxa, mainly Cyclostephanos, Aulacoseira, Cyclotella and Stephanodiscus spp. were abundant in units 1 & 2-a, indicating deep, open lake conditions. Magnetic minerals increased from the base of unit 2 indicating an increasing contribution of Nile alluvium. Benthic taxa such as Fragilaria, Cocconeis, Amphora and Navicula tended to increase towards the core top, from unit 2-b; 3-a to 3-b, indicative of lake shallowing and periods of low Nile floods. Unit 3-c is barren of diatoms and is compatible with terrestrial flood plain conditions. Vegetation was mainly represented by herbaceous pollen throughout most of the core and in the topmost sediment, pollen was scarce but pteridophyte (Osmundaceae) spores increased. Arboreal vegetation had low percentages in most of the record but increased in the middle section of the core (unit 2). A depositional deltaic environment was indicated throughout most of the core (sub-units 2-a & 3-a), where high abundances of Poaceae, Cyperaceae, Chenopodiaceae, Amaranthaceae, Polypodiaceae and Osmundaceae were recorded, indicating high Nile floods and fluctuating rainfall. (C) 2015 Elsevier Ltd and INQUA. All rights reserved.