The Sumerian World

Harriet Crawford, Harriet Crawford

• Editore: Routledge
• Anno: 2013
• ISBN:
  9781136219115
• Edizione: 1
• Argomento: Historia
• Categoria: Historia antigua

The Sumerian World explores the archaeology, history and art of southern Mesopotamia and its relationships with its neighbours from c.3, 000 - 2, 000BC. Including material hitherto unpublished from recent excavations, the articles are organised thematically using evidence from archaeology, texts and the natural sciences. This broad treatment will also make the volume of interest to students looking for comparative data in allied subjects such as ancient literature and early religions.

Providing an authoritative, comprehensive and up to date overview of the Sumerian period written by some of the best qualified scholars in the field, The Sumerian World will satisfy students, researchers, academics, and the knowledgeable layperson wishing to understand the world of southern Mesopotamia in the third millennium.

Part I
The Background

Chapter One
Physical Geography

Jennifer R. Pournelle

Of all the natural factors that impact (or are impacted by) human activity, to fully understand the multi-millennial settlement history of ancient Sumer (and – perhaps more importantly – to understand what of that history is archaeologically visible), it is crucial to understand the dynamic interplay of water and sediments through rivers and marshes, levees and plains, lagoons and estuaries, and, finally, the sea. For without these elements, much of what came to be distinctly “Sumerian” simply would not have been.

The Lay of the Land

The physical stage on which the drama of Sumer’s rise was played was set toward the end of the Pleistocene epoch. As the earth warmed, vast rivers fed by melting ice and heavy rains carved their way through the earlier sediments that had infilled the alluvial basin between the Zagros Mountains of Iran and the Arabian plateau. They dumped those sediments into the Shatt al-Arab valley, creating the floor of what is now the Arab-Persian Gulf. Throughout the early Holocene, even newer sediments then infilled those channel scours. For the most part, this re-leveled the basin floor – in some places burying the earlier surface beneath tens of meters of alluvial sands and silt; in others leaving older remnants exposed, like turtles’ backs rising above the still waters of a pond. Over time, the interplay of tectonic uplift and subduction with rising and falling sea levels, rivers and floods, and windborne sand scouring its way across that silty plain shaped and re-shaped optimal zones for a variety of biological (including human) activities.

An unstable foundation

Water drainage throughout southern Iraq is controlled by a great downward flexure that results from slippage of the Arabian plate beneath the upward-thrusting Iranian Zagros Mountains. This slippage forms an unstable shelf upon which Quaternary alluvial sediments were deposited (Aqrawi, Domas, and Jassim 2006) (Figure 1.1a). The topology of this warped bedrock ultimately influences not only hydrology, but also sedimentation, marine incursion, marsh formation, and the likelihood of archaeological sites being preserved and visible at the surface.

While the entire Mesopotamian zone tips slightly from the northwest (at Samarra) to the southeast (at Basrah), its plane is also twisted northeast toward the Zagros as it is subducted below the great mass of those mountains. Between Najaf and Kut, it further twists west to east along an oblique fault zone. It then turns southeast to follow the course of the Samarra–Amara divide. Finally, near Zubair (old Basra), it assumes a uniform, north-to-south trend (Figure 1.1b).

Thus, waters of the Tigris, down-cutting as they drop onto the alluvium at Samarra, tend to flow south-southeast, always seeking the lowest ground along the base of the Zagros piedmont. Waters of the Euphrates tend to flow west to east, eventually joining those of the Tigris. Both rivers then empty into the Shatt al-Arab estuary, and continue southwards until encountering the Gulf. The combined outflows, passing southward, are slowed by the Zubair sill, behind which fresh water tends to pond, and to which tidal action extends.

A narrow exit

To the west, the alluvial shelf is defined by an abrupt rise in elevation of 10–20 meters to a Miocene limestone plateau, punctuated by small step faults that are most easily visible on the surface at Hit (Buday and Jassim 1987). During wetter periods and seasons, those faults funnel intermittent streams falling from the plateau, creating sediment fans below their nick points, as is clearly visible for the Wadi al-Khar near Hit (Figure 1.1c). The most dramatic of these fans is that of the Plio-Pleistocene Wadi Batin fluvial cone. During drier periods and seasons, windborne sand pours down from the plateau, forming dune fields that are pushed southeastward ahead of prevailing winds (Al-Dabi et al. 1997) (Figure 1.1d). In aggregate, these sediments constrain southerly flow of water, reinforcing the Euphrates’ easterly trend in its search for an outlet to the Gulf (Aqrawi, Domas, and Jassim 2006).

The Mesopotamian Zone’s eastern boundary is sharply demarcated by the folded uplands of the Zagros piedmont. Piedmont sediments, carried downstream during pluvial periods, have deeply buried that boundary in a series of merged alluvial fans that tend to push Tigris waters southward from their southeast-trending flow (Mashkour et al. 2004; Baeteman, Dupin, and Heyvaert 2004/2005). Thus, as the Shatt al-Arab crests the Zubair sill en route to the Gulf, it passes through a sediment-framed bottleneck, where much mixing, scouring, and re-leveling of sediment occurs during river floods and marine incursions.

Alluvial waters and the prograding delta

Understanding the deep structural effects of this twisted bedrock on hydrology and sediment deposition is fundamental to understanding the processes of the twin rivers’ metamorphoses through time. From the eighth millennium BC, at their point of emergence onto the alluvium, the Tigris and Euphrates appear always to have had anastomosing and significantly intermingled flows. Attempts to reconstruct portions of the major fluvial systems from Samarra to Sippar (Northedge, Wilkinson, and Falkner 1989), from Sippar to Kish and Babylon (Cole and Gasche 1998), in the vicinity of Abu Salabikh (Wilkinson 1990), from Isin and Mashkan-Shapir to Ur (Stone 2002), in the vicinities of Nippur and Wasit (Hritz 2010), and from Nippur and Mashkan-

Figure 1.1 (a) The Mesopotamian Zone geosyncline (white hachure) forms where the Arabian plate is forced below the Zagros Mountains. Image: NASA 2001b MODIS. (b) Mesopotamian Zone tectonic subunits. Arrows, hachure indicate tilt direction. (c) Mesopotamian alluvial topology, showing sharp drop to the unstable shelf, and southeast trend tilted toward the Zagros from L. Tharthar to the Gulf. The Wadi al-Khar’s alluvial fan tends to push Euphrates water eastward. Fresh water ponds behind, and tidal flushing extends inland to the Zubair sill (black bar). Manually retouched mosaic of NIMA DTED0 1° quadrangles, with ENVI^TM 3.5 linear stretch (16:243) applied. (d) Boundary uplands. (e) The Shatt al-Arab deltaic system. After Verhoeven 1998, Sanlaville 2003. (f) Contemporary (1) Levees, (2) Crevasse splays, (3) Alluvial soils, (4) Bird’s foot delta. Box: see Figure 1.2a.

Shapir to Uruk (Steinkeller 2001) do not indicate the proportion of the Tigris’ overall contribution to alluvial settlement and irrigation before the third–second millennia BC. However, there is no evidence that either river established its present meandering channel beds at the latitude of Felluja and Baghdad before the early second millennium (Verhoeven 1998: 160; Heyvaert and Baeteman 2008). Even then, at least one branch of the Euphrates still flowed eastward to the Tigris (Gasche and Tanret 1998). How then should we interpret physical evidence for hints of the rivers’ earlier evolution?

As the surface slope of alluvial channels levels off – either because the land itself levels, or because their channels empty into a large body of water – river beds undergo threshold changes from braided, to meandering, to straight or sinuous, with the latter in some cases assuming multi-channel, anastomosed patterns (Baker 1986: 257–259 and figs. 4–5; Schumm and Khan 1972). Thus, in Mesopotamia, braided channels are typical of the arid uplands, where the Tigris and Euphrates are deeply incised into the Syrian and Arabian plateaus. However, on dropping from those stable shelf lands into the alluvium, the slope abruptly diminishes to less than 1 percent. There, the rivers assume meandering courses through the river floodplain, within fairly stable banks (Figure 1.1e).¹ Over time, as they alternately carve through and re-deposit silts, sands, and gravels, these meanders leave fossil traces up to several kilometers wide, characterized by concentric stripes on their crests (Gasche and Tanret 1998: 5–7). Those contours can be preserved for millennia, due in part to their durable function in shaping subsequent agricultural systems, as they delineate systems of irrigation dikes and levees that both trap silt and demarcate field and crop boundaries. Down the upper Mesopotamian alluvium, such relict meandering systems are visible within the relatively narrow belts of their archaic floodplains (Pournelle 2003a).

This leaves in question whether, where, and to what extent it is possible to associate any relict channels with earlier periods. The Ur III period Tigris/Euphrates admixtures mentioned above could have existed in substantially the same beds for millennia. Conversely, subsequent sediments and channel migrations may have obliterated any (surface) remains. To assess which of these scenarios is more likely, we must first note that, on passing from the slightly tilted Tigris sub-zone to the nearly flat Euphrates sub-zone, the slope falls to less than 0.5 percent. There, along the transecting slip faults, the Tigris and Euphrates rivers tend to branch into multiple, sinuous distributaries with weak banks. From this point southeastward, channels leave few (if any) relict meander scrolls. Instead, connectivity among levees, avulsive splays, and deltaic mouths must be used to chart relict river systems.

Most sediments are dropped in flood deposits along river distributaries, over time building broad, weak levees. Today, the largest of such alluvial levees lines the Shatt al-Arab, where the conjoined rivers form an estuary once famed for its millions of date palms (since destroyed during the Gulf Wars) (Figure 1.1f). Because alluvial soils comprise the best-drained agricultural soils (Buringh 1960; Wirth 1962), direct association of these levees with past agricultural activity is common (Wilkinson 2003) (Figure 1.2a and b). Chains of sites situated along their tops can indicate the system date, as for those of the second millennium BC systems of the Third Dynasty of Ur analyzed by Hritz (Hritz and Pournelle in press).

Where weak levees break (or are broken by human intervention), avulsions can become the source of new or diverted main channel flows (Figure 1.2c). However, just as often, the sudden fanning drops sufficient silt that the natural levees reestablish when floodwaters recede. Sites located at the head of floodsplays, where dramatic annual flooding would make permanent habitation hazardous and unlikely, can serve as a termini post quem for active inundation from the breach, and thus the system of which they form a part. However, sites located within such splays are ideally situated to take advantage of floodbasin cultivation and pasturage (Pournelle and Algaze in press) (Figure 1.2d).

Finally, as rivers abruptly slow on encountering slack water, they dump their remaining sediment loads, resulting in the multiple, bifurcating channels of a “bird’s foot” delta, with newly deposited sediments becoming webs of marshland between the toes (Figure 1.3a). This can be seen at Warka (Uruk), where satellite photos reveal the city’s placement not so much on the river as in it: the city’s walls are clearly surrounded by a relict bird’s foot delta extending into spring 1968 Euphrates floodwaters (Figure 1.3b).

Through time, this process of channel bifurcation, sediment dumping, and channel extension builds sediment lobes that infill older channels around turtlebacks (the isolated fragments of older surfaces that protrude above the floodplain) and contribute to channel-flipping (as distributaries become blocked by their own sediments). To better understand this dynamic interaction of water and sediments over time, we must consider the profound effects of sea level on the hydrological regime.

Figure 1.2 (a) Tigris south of Amara (Qalat Salih-al-Azair). The cultivated agricultural zone extends outward from the water channel along the levee system. Excess water drains through light-colored tails of smaller canal levees into seasonal back swamps visible as silty, dark grey bodies. Only two centuries ago these rice fields were year-round marshlands (Westphal-Hellbusch and Westphal 1962: 39–40). (b) Outlines demarcate relict levee between sites WS375 and WS400. Better-consolidated levee soils are less waterlogged, and hence appear lighter in color.
CORONA KH4B_1103-1A-D041-055; KH4B_1103-1A-D041-058 (May 1968).
(c) The Kut barrage on the Tigris between Sheikh Sa’ad and Ali al-Gharbi drains floodwaters into Lake as Sa’adiya (Haur as Sa’adiya). The barrage maintains and augments a natural avulsion (floodsplay) (compare Buringh 1960: 181). As floodwaters recede, wetland villages (circles) stockpile fodder (reeds and grasses), and transhumant pastoralists graze livestock en route to the Zagros piedmont. (d) Flanked by modern fields, a relict avulsion south of Wilaya is cross-cut by more recent Parthian–Sassanian canals associated with sites WS901 (T...