The Sumerian World (Routledge Worlds)

Marine incursion, backswamps, marshes, and estuaries

From the early Holocene, after rising at a (geologically) “rapid” rate of about 1. 8 cm per
year for two millennia, by 6150 (cal) BCthe head of the Arab-Persian Gulf reached
approximately its current level. For the next three centuries, throughout the ‘Ubaid 0 ,
that rate slowed. At that time, ancient marshes extended as far southeast as Tello
(Girsu), and the rivers laid down sediments in the Euphrates Valley from Ur to Fao
(Bird et al. 2010 ; Aqrawi and Evans 1994 ; Aqrawi 1995 ; Hritz, Pournelle, and Smith
2012 a). For the next four centuries, as sea level rise slowed to a near halt, the delta
expanded, and marshes continued to form. Following this interim stillstand, by 5450
(cal) BC, sea level rise resumed at a rate of a half-meter per century (a half-centimeter
per year), and continued to do so for the next millennium.
Through the remainder of the ‘Ubaid, the sea rose another 2 – 4 m, reaching a
highstand of approximately 2. 5 m above that of today. By 4550 (cal) BC, the sea had
completely swamped the Euphrates Valley and the ancient marshes, and extended as
far inland as Ur (Figure 1. 4 , Figure 1. 7 ). Thus, at the dawn of the Uruk period, the Gulf
having halted at its maximum level, the rivers began another round of marsh-
and delta-building, stretching inland at least as far as the foundations of Uruk itself
(Aqrawi 2001 ; Brückner 2003 ; Plaziat and Sanlaville 1991 ). Sea levels remained stable
throughout the Uruk and Jemdat Nasr, regressed slightly at the beginning of the Early
Dynastic, and then returned to their highstand. That eustatic stability over roughly two
millennia had profound implications for that area called “the heartland of cities” by
Robert McC. Adams in his definitive 1981 study (Adams 1981 ). Before Adams, the
presumption that cities arose on the Mesopotamian alluvium because ofmastery of

–– Physical geography ––

A B

Ur Gate and levee

Basra Gate and levee

Figure 1.3(a) Amara, straddling Tigris distributaries arrayed in a bird’s foot delta extending into

surrounding marshlands (Buringh 1960 : 187 ). (b) Warka (ancient Uruk), straddling a relict bird’s

foot delta extending into spring Euphrates floodwaters (black). As late summer heat dries

surrounding marshes and lowers the water table, lower areas and infilled drainage are marginally

wetter, and therefore darker. Less permeable, higher, and drier built-up areas, levees, and

consolidated canal beds appear lighter in tone. CORONA KH 4 B_ 1103 - 1 A-D 041 - 065

(May 1968 ); KH 4 B_ 1107 - 2170 DA- 139 (August 1969 ).