From the Field
Dr. Rebecca Miller (Spring 2015 Grantee), with co-investigators Dr. John Stewart and Dr. Keith Wilkinson, completed this summer’s Leakey Foundation funded field season at the site of Trou Al’Wesse in Belgium. With an enthusiastic and meticulous team of students from the University of Liège, Bournemouth University and Winchester University, as well as two students doing doctoral and Master’s research on paleoecological and geological aspects of the site (Monika Knul, PhD student from BU and Eden Richards from U of W), this season was particularly productive.
Trou Al’Wesse (“Wasp Cave” in Walloon) is a large cave on the Hoyoux River, a tributary of the Meuse River, located near the village of Modave. It extends back ca. 45 m and connects to a karstic network, with a chimney open to the surface above (formerly filled with deposits excavated in the 19th century that yielded a multiple Late Neolithic burial). Facing southwest, it overlooks the alluvial plain of the Hoyoux. It is situated in the nature preserve owned by Vivaqua, a major Belgian water company with a strong sense of responsibility of cultural and natural preservation. The nature preserve protects many rare and threatened species, including several bat species that hibernate at Trou Al’Wesse. Additionally, they are owners of the nearby Château de Modave, principally 17th century although occupation dates back to the early 13th century. Finally, Vivaqua has been a generous supporter of the Trou Al’Wesse project since the beginning, providing logistical support and assistance in protecting the site.
The Leakey-funded excavations took place on the cave terrace, focusing on the Middle to Upper Paleolithic transition in units 17 and 16. The chronological focus of the terrace excavations is the MP-UP transition and the Early Upper Paleolithic, from roughly 50,000 to 30,000 BP. In the Pleistocene sequence, this includes units 17 (Mousterian) and 16 (non-archaeological but fauna-rich unit) underlying unit 15 (Early Upper Paleolithic with Aurignacian layers). The principal objective is to study the climatic and environmental context and chronology of human occupations across the MP-UP transition in order to evaluate the factors affecting Neanderthal extinction and the arrival of the first modern humans in northwest Europe. Trou Al’Wesse is the only site in Belgium currently known and one of the rare sites in Northwest Europe with an intact (i.e., unexcavated) stratigraphy covering this period. It is also comparable in cave morphology and size to the eight Belgian sites that have yielded Neanderthal human remains (Engis, La Naulette, Fonds-de-Forêt, Grottes de Goyet, Grotte de Spy in the 19th century and Trou de l’Abîme à Couvin, Grotte Scladina, and Grotte Walou in the late 20th century), suggesting the possibility of discovering new Neanderthal remains in stratigraphic context using modern methodology and techniques.
The goals for the 2015 season were to excavate the Neanderthal occupations with Late Mousterian lithic assemblages in unit 17 and non-archaeological unit 16 on the TAW terrace, collect data to study climatic and environmental variability, clarify the stratigraphic sequence of these units 17 and 16 (previously excavated only in the 1990s in a limited area on the terrace), select bone and charcoal samples for AMS dating of this sequence and collect sediment samples and install dosimeters for OSL dating.
The season was quite successful, with unit 17 containing Mousterian layers extremely rich in lithics, fauna, burned bone and charcoal and unit 16 proving to be very complex with several layers that will provide information on climatic oscillations during a phase in which humans were absent from the site.
On the terrace, units 17 and 16 in the M row squares were excavated, starting with M6 (next to M5, which was excavated in the 1990s) to M10, 4 m further from the cave entrance toward the alluvial plain and the Hoyoux River. Half-squares were also opened in M7, M8 and M9 to excavate unit 16. The richness of the Mousterian layers was immediately shown in M6, where, in a single 50x50x25 cm subsquare (M6C), in layers 17a and 17b, more than 700 lithics and bones were recorded in 3 dimensions and many more found during water-sieving to 0.5 mm. Adjacent subsquare L6D was also opened and proved to be as rich. This density necessarily slowed down the expected rate of advancement (initially, our goal was to excavate squares M-N 6-10). At the end of the season (as always!), the top of the Mousterian unit was reached in squares M10 and M9. The Mousterian occupation area extends across the entire zone on the terrace and will be further investigated in spring 2016 and during the summer 2016 field season.
Excavation also continued in a sample column begun in 2014 by M. Knul (BU) and E. Richards (U of W). In 2014, the column had nearly reached the contact between units 15 and 16. Faunal remains here are often much larger, likely due to rapid redeposition and also the probable location of rows up to at least row 6 beneath the former overhang of the cave or even inside the cave entrance. Cryoclastic activity has caused major collapse from the cave face, creating the clast-based Pleistocene deposits on the terrace. Bones identified in the field include woolly rhinoceros, cave bear, horse, reindeer, red deer, arctic fox, mustelids, lemmings, voles, fish and birds.
The Mousterian lithic assemblages from layers 17a and 17b include many tools (sidescrapers, retouched flakes), core fragments, core preparation and reduction by-products and tiny flakes and splinters. The raw materials used are varied: several varieties of fine and medium-grained flint, flint river cobbles, good quality phtanite, fine-grained quartzite. Raw material sourcing is in progress, although the phtanite source is already known to be non-local, in the Ottignies-Mousty region about 70 km WNW (across the Brabant and Hesbaye Plateaux where at least some of the flint is likely to be from, and crossing the Meuse River, where river cobbles would have been available on the river terraces). The lithics are unpatinated and have fresh edges and ridges, suggesting rapid deposition and little post-depositional movement. For subsequent use-wear and residue analysis, none of the artifacts have been handled or processed. Refitting analysis has a good probability of success and will be done after the use-wear analysis.
Bone remains are abundant, ranging from fragments to larger elements. Significant amounts of burned bone and charcoal fragments were also present in layers 17a and 17b, although no hearth features have as yet been found.
In unit 16, faunal density varies by layer and analysis of the small mammal fauna in particular will contribute to reconstructing the climatic sequence. Larger fauna so far includes woolly rhinoceros and cervids, identified in the field; faunal analyses are in progress.
In addition to the Leakey-funded part of the project, the excavation of two test pits TP2005 and TP2013 inside the cave was continued. The layer currently reached in TP2005 contains cave bear remains apparently representing a hibernation den. In TP2013, after removal of several phases of backfill from 19th and 20th century trenches and a tunnel, the unexcavated Pleistocene layers yielded an Aurignacian endscraper on a long large blade, indicating that the cave deposits will also contain Aurignacian and very likely Mousterian occupations.
Samples will be selected for AMS dating based on stratigraphic layer and identification (e.g., species or bone tool) as well as those directly associated with sediment samples collected for OSL dating. For OSL dating, two specialists working with Johannes Van Der Plicht (Leiden University), Tony Reimann and Christina Ankjaergaard from Wageningen University, came to Trou Al’Wesse and collected sediment samples and inserted dosimeters.
We are now busy with lithic, faunal and geological analyses, sample selection for AMS dating and post-excavation processing and sorting of water-sieved sediments. Over the next several months, we will start to have a clearer picture of the stratigraphic sequence, palaeoenvironmental change and Neanderthal activities during the Late Mousterian. In addition, preliminary talks will be presented at the annual Journées d’Archéologie wallonne (November 19-20, Rochefort) and FNRS “Prehistory” Contact Group meetings in Belgium (December 13, Malines).
