Fig 1.
(a) Geography of Mesopotamian Plain (dashed black line) and its joint watershed (black line).
Modern localities mentioned in text (black-filled circles respectively). Drill core location at Lagash in shown as red-filled circle; (b) Natural vegetation [7]; (c) Precipitation [8]; (d) Soils [9].
Fig 2.
(a) Large-scale morphology of the Mesopotamian Plain based on Copernicus Sentinel data [10].
For altitudes, rainbow colors repeat every 10 m from 0 to 50 m in height; lands higher than 50 m are in gray; (b) avulsion node at Kut with historically-attested courses is shown in a gray-scale slope representation of the terrain model (higher slopes are lighter); (c) morphological elements of the confluence zone between Tigris and Khuzestan rivers; (d) the Eridu basin.
Fig 3.
Depositional environments interpreted from litho-, bio-, and chemo-stratigraphy of Lagash drill core.
In-situ radiocarbon dates (in thousands of years) are shown with red arrows. Paleoenvironmental proxies: total organic carbon (TOC); ostracods and foraminifers (present/abundant with short/long black bands respectively); bromine (Br); gypsum (red bands); and sulfur (S).
Fig 4.
Calibrated radiocarbon dates from Iraqi cores [15,17,29,30] relative to the global sea level index points (from [31] shown as grey dots): (a) Lagash core (OC – organic carbon; IC – inorganic carbon); (b) previously reported and recalibrated.
The highstand in the global dataset is confirmed by Persian Gulf data and the lowering trend since c. 6000 years ago [32] is indicated here by the black line in (b).
Fig 5.
Evolution of the Mesopotamian delta complex composed of the axial-oriented Sumer lobe (S), Euphrates (E) and Tigris (T) lobes and Shatt al-Arab (SA) as well as the transversal Khuzestan fan-delta (K).
Sumerian cities larger than 100 ha are shown with inferred maximum flooding limit (MFL). Upstream from the MFL, maximum tidal reaches are shown as MTR200 and MTR100 when the backwater zone in is assumed at 200 km (e.g., similar to Shatt al-Arab) and 100 km, respectively. The upper inset describes the lobe morphology, and the lower inset shows estimated time spans for delta lobes relative to cultural phases in Sumer.
Fig 6.
Sequential historical geography of coastal Mesopotamia at: a. 7,000, b. 6,000 and c. 4,000 years ago.
Inferred directions of fluvial systems (black arrows) responsible for building the Mesopotamian delta complex are shown with their tidally-influenced zones (in green).