Research ArticleANTHROPOLOGY

The second century CE Roman watermills of Barbegal: Unraveling the enigma of one of the oldest industrial complexes

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Science Advances  05 Sep 2018:
Vol. 4, no. 9, eaar3620
DOI: 10.1126/sciadv.aar3620
  • Fig. 1 Location and reconstruction of the Barbegal watermill complex.

    (A) Overview map. k, karst springs. (B) Detailed map of the small red rectangle in (A). The southern aqueduct (light blue) fed into the mill complex. Blue arrows indicate flow directions. Dotted lines: contour lines (m). (C) Proposed reconstruction of the complex, consisting of two parallel rows of watermills in open-air conditions, built on a hillslope. (D) Alternative reconstruction proposed in this study, where the watermills were enclosed within buildings.

  • Fig. 2 Selected carbonate fragments from the woodwork of the Barbegal watermills and reconstruction of their original positions.

    (A) Possible reconstruction of a water wheel and flume based on the fragments found and other Roman watermill reconstructions (26, 40). (B) Fragment N123, a slab from a flume sidewall with clear impressions of wood. (C) Fragment N140, representing the base of a millrun flume. The reconstruction of the flume shows the wood side in yellow and the water side in blue. The position of fragment N126 in a similar flume is indicated. (D) Fragment N126 from a side wall slab showing a 45° angle connecting the bottom and sides. The top (left side) of the deposits is micritic and porous (m), while the main deposit is sparitic (s); the sharp transition is marked by a red dashed line. (E) Fragment N81, which grew around a spoke of a water wheel, with a square-shaped opening where the slab had been attached. (F) Fragment N138, interpreted as the impression of the bucket of a water wheel. (G) Fragment N83, deposited around a wooden pole, as apparent from the central hole, with a conically shaped top, for which the original position remains unclear. Photographs by P.L.

  • Fig. 3 Microstratigraphic correlation of carbonate fragments.

    (A to C) Fragments N90, N109, and N133 with a reconstruction of originally attached wood and adjacent deposits. Blue and red lines connect layers in the three fragments that were formed simultaneously, although the fragments were not part of a continuous deposit and the thickness of the layered calcite deposits differs among the three fragments. Fragments N109 and N133 are shown at different scales. The red dashed line marks an unconformity. (D) Schematic presentation of the microstratigraphy of the three fragments, with variably present microstratigraphic sections I, II, and III. Section III is present in all three fragments, section II is only present in fragments N90 and N109, and section I is exclusively present in fragment N109. This is attributed to different growth periods for each fragment, N109 being the most complete and N133 being the least complete. All three fragments were capped by porous calcite of variable thickness, indicated in white. (E) Fragment N90 formed on part of a wheel, and the negative wood imprint is clearly visible. The top left corner was polished and is shown in (A). (F) Schematic reconstruction of the millwheels and flumes showing possible locations of the three fragments. (G) Fragment N133 originates from the bottom of a millrun channel. The fragment shown in (C) was taken from the front as indicated by a blue dashed line. Photographs by C.W.P.

  • Fig. 4 Stable isotope composition of representative carbonate fragments N133 and N109 from the Barbegal mills.

    (A) Sample of fragment N133 with micromill trace and associated stable isotope profile. Position of close-ups (A1) and (A2) marked by white squares. The sample is mostly sparitic with a sharp transition to a micritic top. Fragment N133 yielded irregular truncated isotope curves. Yellow lines mark the truncation sites where operation of the mills was likely interrupted. (A1) Close-up of the side of (A) showing a sharp transition, marked with red lines, from dense sparite (s) to porous micrite (m) with plant imprints (p), formed from decayed plant matter at the top of N133. (A2) Thin-section image of truncation surface #5 in sparite of sample N133, coinciding with a truncation in the stable isotope curves. bb, brown bands in sparite. Crossed polarized light. (B) The isotope pattern of N133 was replicated in fragment N109 and has a longer stratigraphy than fragment N133. Red line in (A) and (B) marks the same stratigraphic level in the stable isotope graphs. (C) Comparison of a carbonate deposit from the Roman aqueduct of Aspendos (Turkey) showing a highly symmetrical pattern [modified after (14)], whose δ18O cyclicity is attributed to seasonal, temperature-controlled isotope fractionation (D). W, winter; S, summer. (E) The Barbegal stable isotope time series record interruptions, mostly during late summer and autumn, giving rise to truncated curves (F), marked by yellow lines in (A) and (B). VPDB, Vienna PeeDee Belemnite. Photographs by C.W.P.

Supplementary Materials

  • Supplementary Materials

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    • Fig. S1. Sample of fragment B3 from the wall of mill basin E4, with micromill trace and associated stable isotope profile.

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