Bettina Arnold - Heuneburg Archaeological Project: 1999 Report

A Landscape of Ancestors: The Heuneburg Archaeological Project

Preliminary report of the 1999 excavation of a Hallstatt tumulus in the Hohmichele ("Speckhau") mound group, Markung Heiligkreuztal, Gemeinde Altheim, Landkreis Biberach

Bettina Arnold, Matthew L. Murray, Seth A. Schneider

Abstract

In the summer of 1999, a team of American archaeologists from universities in Wisconsin, Minnesota, Illinois, and New Mexico began excavation of Tumulus 17, one of at least 36 mounds belonging to the so-called "Speckhau" group near Hundersingen in southwest Germany. The Speckhau group includes the Hohmichele, which is the second largest Iron Age mound in western Europe. This mound was chosen for excavation in consultation with Professor Dr. H. Reim and Dr. S. Kurz of the Baden-Württemberg Landesdenkmalamt (State Monuments Office), Tübingen branch. The excavation of Tumulus 17 is part of a larger, long-term research project based at the University of Wisconsin-Milwaukee, USA with the title "A Landscape of Ancestors." The project combines analysis of ancient DNA (aDNA) from previously excavated skeletal material from the Heuneburg vicinity with conventional mortuary analysis to address questions regarding early Iron Age social organization and funerary rituals. In addition, the structure and construction of the mound will be studied systematically in order to supplement the relatively limited data set currently available for mounds of early Iron Age date in the Hohmichele group.

Project Description

Tumulus 17, which is over 20m in diameter and stands approximately 200m southwest of the Hohmichele, was chosen as the focus of investigations for a variety of reasons. Its size and proximity to the Hohmichele strongly suggested a Hallstatt date for the tumulus. Due to evidence of past disturbances and on-going gradual disintegration of the mound through animal burrowing and tree root incursion, a complete and systematic recovery of the remaining information from the mound was recommended by the Landesdenkmalamt.

Tumulus 17 at the beginning of excavation

During the 1999 excavation the mound was divided into four quarters, each composed of several excavation trenches. Standing profiles were established across the interior of the mound. One half of the mound was excavated, including the entire northwest and southeast quarters of the tumulus and encompassing approximately 1,188m³ of mound fill (Figure 1). Initially, excavation proceeded in small exploratory trenches along the north-south grid axis adjacent to the standing profiles. Once a sense of the mound stratigraphy was obtained through trenching, excavation was expanded to encompass each complete quarter, which was systematically removed in regular intervals or excavation plana. The 1999 excavation continued at least 20cm into the subsoil below the cultural deposits along each standing profile in order to expose as complete a cross-section as possible. Excavation was undertaken largely by hand, although a small mechanized backhoe was used for final trenching along the standing profiles.

Excavation yielded no evidence of a formal demarcation of the mound limits through a trench, stone setting, postholes, or other features. The excavated diameter of the mound based on calculations from the completed profile drawings proved to be approximately 20.86m. Earlier reports had suggested a larger diameter of 27-29m (Kurz and Schiek n.d.). Similarly, while the estimated preserved height was originally reported to range between 1.9m and 3.2m, the excavated preserved height from the ancient ground surface to the current apex of the mound was about to 2.7m (based on the northwest quadrant's south profile drawing). The total absence of any kind of demarcation of the mound foot is notable but not unique; the Hohmichele also lacked a ditch, row of posts, or stone circle around its base (Riek 1962). The original perimeter of the mound was therefore identified through observation of soil changes, and the actual diameter was calculated from profile drawings (Figure 2.1).

History of Investigation

Prior to excavation, Tumulus 17 was largely intact, preserved to a height of nearly 2m, but it showed the scars of various recent disturbances. In 1893, A. Witscher of the Landeskonservatorium dug into at least two tumuli in the Speckhau group. This activity may have included Tumulus 17 and nearby Tumulus 18, just on the other side of a logging road, but it is no longer possible to differentiate between the two in excavation archives. The truncation of Tumulus 17 may be the result of Witscher's probing, which produced the remains of a decorated ceramic vessel that is no longer in existence (Kurz and Schiek n.d.). The Douglas fir on top of the mound is about 100 years old (Jehle pers. comm.). It clearly post-dates truncation of the mound and therefore may have been planted shortly after Witscher's exploration. The disturbance surrounding the roots of the tree does not seem to extend all the way to the ancient ground surface in the center of the mound, but it does reach into the charcoal-rich zone of Stratum 5 which contained large fragments of Alb-Hegau tradition burial pottery, such as sherds with red-slip, graphite, and characteristic incised decoration. The fragments of a decorated vessel reported by Witscher could very well have been pieces similar to the Alb-Hegau pottery uncovered during 1999 excavations.

Project Results

The results of excavation in 1999 were extremely interesting. Due to the large size of the mound and its apparent early Iron Age date, secondary burials were expected in addition to a significant central interment; however, no formal burials were discovered, although traces of a large central chamber or enclosure were uncovered in the final days of excavation. One of the most interesting results of excavation was the evidence of mound structure and construction (Figure 3), including numerous features such as charcoal stains and small artifact concentrations indicating that activities were undertaken at the mound subsequent to its original erection. Excavation revealed a distinction between a relatively homogeneous outer mantle of fill and a highly stratified and variable inner mound core, suggesting multiple phases of mound construction.

Outer Fill Mantle

The stratigraphic contexts or strata that were observed during excavation of the outer fill mantle are described below. Stratum 1 consisted of a thin layer of root mat and topsoil. Strata 2 and 3 represent the outer mantle of mound fill which was up to 150cm thick. Stratum 2 is a transitional soil with decreasing organic content. Stratum 3 appears to be relatively homogeneous mix of spoil from the mound's surroundings. Few artifacts, mostly pottery, were found in this stratum. The isolated sherds are often heavily exfoliated and are probably from disturbed pre-mound settlement contexts. Similar secondary deposits of bronze Age pottery were reported from the mound fill of the Hohmichele (Riek 1962). One small fragment of sheet bronze was also found in Stratum 3.

Tumulus 17 - Feature 10 (Charcoal and Burnt Bone)

Six types of secondary cultural features were identified within the outer mantle of mound fill (Stratum 3). These features represent activities undertaken at the mound subsequent to establishment of the central chamber or enclosure and construction of the inner mound. Most secondary features in the outer mantle were Type 1, small charcoal lenses or stains (Features 2, 3, 4, 7). These stains were between 30cm and 70cm in diameter, contained small flecks of charcoal and occasional larger pieces, but yielded no additional cultural materials. Some of the stains consisted of groups of smaller charcoal "packets." The stains appear to be similar to the so-called "Holzkohlennester" observed in the Hohmichele (Riek 1962; Kurz and Schiek n.d.). Because of the concentrated nature of the charcoal, it is unlikely that the stains are the result of redeposited settlement debris or cremation burials inadvertently included in the mound fill. There is no evidence that the charcoal has been introduced through animal or root activity. The features appear to be intentional deposits and may represent the remains of small hearths (altars?) that were used briefly and then abandoned. Feature 12 (Type 2) contained several charcoal lenses and burned earth in a basin-shaped depression visible in the south profile of the mound. This feature may be interpreted as a hearth or altar. Feature 6 (Type 3) consisted of a charcoal concentration associated with a scatter of early Iron Age pottery at the boundary between the outer mantle and the inner mound. Type 4 was a small "nest" of pottery and charcoal placed on foundation of sorted egg-sized pebbles (Feature 8). The soil matrix appears to have been burned. This feature may also represent the remains of a hearth or altar. Feature 11 (Type 5) consisted of a concentration of charcoal, burned earth, and pottery fragments from a single vessel, most likely a bowl. Feature 23 (Type 6) was a small stone setting or pebble pile in the southeast quarter of the mound. No charcoal or other cultural materials were found in association with the pebbles, which appear to have been intentionally placed within the mound fill. The function of the pebbles is not clear.

As noted previously, Tumulus 17 may have been partially excavated in the late-nineteenth century by A. Witscher. A funnel-shaped disturbance in the center of the mound is partly visible in the standing profiles of the 1999 excavations. It extends at least 1.5m below the current mound surface and may represent a looter's shaft. As a result of disturbance from the aggressive roots of the massive Douglas fir, it is not clear if the shaft originally continued into the mound's central enclosure. Other more superficial disturbances to the mound include Features 13 and 25. Feature 13 is a large pit visible in the south profile of the northwest quarter which yielded charcoal, a wire nail, and pieces of a slag-like material. The pit ended at the base of the outer mantle of fill. Feature 25 was a shallow depression lined with sheet metal that was found during a shallow backhoe sondage in the northeast quarter of the mound. This pit also did not extend below the outer mantle. A similar disturbance containing fragments of sheet metal was visible in the east profile of the northwest quarter extending into the upper portion of the inner mound. These disturbances appear to date to the late-nineteenth or twentieth century after truncation of the mound and therefore they may be related to Witscher's investigations. The discovery of ubiquitous glazed folk-pottery post-dating the 16th century along the foot of the mound may suggest that looting also was attempted as much as 400 years ago. A variety of debris from the late-nineteenth and twentieth centuries was also recovered.

Inner Mound

NW quadrant inner mound stratigraphy in planview

The inner mound structure begins with Stratum 4, a strikingly homogeneous and dense layer of gray clay loam containing very few rocks or pebbles. Stratum 4 was a maximum of about 70cm in thickness. The transition between Stratum 3 and Stratum 4 is marked by an irregular lens of oxidized minerals leached from the upper mound fill and deposited at the abrupt change between permeable and non-permeable soils (Figure 2.2). Stratum 4 contained few artifacts except at the boundary with underlying Stratum 5. No cultural features were observed in Stratum 4.

NW quadrant stratigraphy in planview (note charcoal)

Stratum 5 corresponds to Features 1, 5, 9 and 10 on north side of mound (these were eventually collapsed into Stratum 5 after it was recognized to be a single stratigraphic context). Stratum 5 was generally 5-10cm thick. In planview, Stratum 5 consists of a ring-shaped concentration of charcoal with flecks of cremated bone with early Iron Age ceramic fragments mainly distributed at the outside margins of the ring along the edge of the transition between Strata 4 and 5 (Figures 2.1 and 2.2). This pattern could represent the deposition of basketfuls of funeral pyre sweepings including portions of pottery vessels, with the potsherds tending to erode or slide toward the bottom of the mound. The largest pottery fragments appeared in the lowest levels of this stratum toward the foot of the mound, further strengthening this hypothesis. Many of the potsherds in this stratum were fire-damaged. Several burned fragments of iron and bronze were recovered from this stratum as well. Stratum 5 produced more metal finds on the south side of the mound than anywhere else within the structure.

Stratum 6 consists of a relatively thin (10-40cm thick) layer of brownish silty clay loam between the gray clay loam of Stratum 4 and the inner core of the mound. Occasional charcoal flecks or large pieces of charcoal were found in this stratum. Finds from both sides of the mound consist of isolated pottery fragments that were not associated with identifiable features within the layer.

Below Stratum 6 the composition of the inner mound core becomes increasingly heterogeneous and difficult to reconstruct. Strata 7-15 present a challenging interpretive puzzle, which may not be resolved until the remaining portions of the mound are excavated. The stratigraphy becomes markedly complex with increased depth and proximity to the center of the mound, partly a result of disturbances from the Douglas fir, animal burrowing, and an apparent looter's trench. Morphological distinctions were used to determine strata since it was often impossible to discern stratigraphic relationships during excavation. Stratigraphic differences between the northwest and southeast quarter excavations also increased, inhibiting correlations between mound strata.

Tumulus 17 - Feature 16 (Charcoal Concentrations)

Two types of secondary cultural features were detected in the interior fill of the mound. These features are remains of activities that probably occurred as part of the original mound construction, but it is not always clear if they were deposited before or after establishment of the central chamber or enclosure. In contrast to features in the outer mantle of fill, most of these deposits appear to be distributed on a horizontal plane at a depth of approximately 2.40m beneath the apex of the mound, presumably representing an ancient surface on which a complex series of mortuary activities were performed. Prior to the deposition of Stratum 5, several large, dense concentrations of charcoal were formed or placed near the center of the mound. A complete but fragmentary bowl was recovered near the inner edge of Stratum 5. Only one fragment of pottery was recovered in this interior area, just inside the central enclosure.

The first type of interior fill feature was identified in the northwest standing profile of the mound and consists of a small pile of egg-shaped pebbles below Stratum 5. The remaining interior fill features consist of very dense charcoal deposits (Type 2: Features 15 and 16). These features were found near the base of the inner mound just above or adjacent to the central enclosure. Feature 15 is a charcoal and ash concentration in the southeast quarter of the mound at a depth of 2.30m. Feature 16 consists of three charcoal concentrations in the northwest quarter at a depth of 2.35m. The concentrations were found just above and to either side of a rectilinear ditch in the subsoil demarcating the central chamber or enclosure. One of the concentrations contained a small piece of burned bone. The deposits of Feature 16 may represent remains of a funeral pyre within which a central chamber was established and over which the original mound was erected.

Central Enclosure

Tumulus 17 - Rectangular ditch enclosure

Tumulus 17 - Posthole at the enclosure corner

At a depth of 2.55m below the top of Tumulus 17, excavation uncovered a narrow rectilinear soil stain in the center of the mound (Features 17 and 22). This feature is the bottom portion of a rectangular ditch enclosure evident in both excavated quarters of the mound. The ditch appears to demarcate the central area of the mound and suggests the presence of a primary burial chamber. The ditch fill consists of the same grayish material as the lower portion of the inner mound core, while the yellowish sterile soil of Stratum 10 is redeposited material from the excavation of the ditch. A posthole is evident at each corner of the enclosure, but there is no evidence of a superstructure within the ditch itself. No cultural debris was recovered from the excavated ditch fill.

Although no clear evidence for a primary burial was uncovered within the enclosure, a series of four stains and one depression feature was identified within or adjacent to the enclosure extending into the sterile subsoil. Features 18, 20 and 21 are irregular and poorly defined soil stains in the northwest quarter of the mound that contained small amounts of charcoal. These stains may be cultural, but they were difficult to distinguish from animal burrows, root decay, or natural soil variations. Feature 24 consists of several small, roughly circular charcoal stains in the subsoil outside the enclosure. The stains may represent remnants of Features 15 and 16, which have been mixed into the underlying subsoil through biomechanical processes. Feature 19 is a shallow depression that extended into the south standing profile in the northwest quarter of the mound. It is the only clearly defined feature identified within the rectangular ditch. A small portion of the depression excavated in 1999 was 20cm deep and yielded no cultural material. Most of the feature appears to be intact within the standing profile and awaits future investigation.

Discussion

The central enclosure within Tumulus 17 is oriented with each of its sides toward one of the four cardinal directions. The dimensions of the enclosure can be estimated at 5x5m based on the position of the postholes at the ditch corners. Since evidence of a primary burial was not discovered in 1999, it is not clear if the central grave was a cremation, inhumation, or both. The enclosure seems rather large for a cremation grave, and in fact according to Kurz and Schiek (n.d.), the central burials of Iron Age mounds associated with the Heuneburg are invariably inhumations. This observation, however, raises the question of the origins of the cremated bone fragments found in association with the charcoal "nests" and the dense layer of charcoal and pottery identified as Stratum 5. It is assumed that the burned bone is human in origin, although the fragments are generally too small to be identifiable. They have been submitted for testing. None of the features are large enough, nor do they contain enough cremated bone, to be considered formal cremation graves. Their concentrated nature and patterned distribution, on the other hand, mitigate against the suggestion that they represent disturbed and redeposited cremation graves from the borrow pits in the immediate vicinity of the mound that yielded soil for the tumulus fill (cf. Kurz and Schiek n.d.). Areas of burned earth in association with charcoal concentrations that suggest in situ burning are known in Hallstatt period mounds in Baden-Württemberg, such as the tumulus cemetery of Böblingen which is partly contemporaneous with Tumulus 17 and is located only about 45 km from the Heuneburg (Bittel, Kimmig and Schiek 1981:308-310). Tumulus 11 at Böblingen contained an area of burned clay just under 1m in length (Zürn 1979:60). This area of burned clay appears to have been located on the ancient surface and could have been associated with a disturbed context unconnected with the mound. In the same mound group, Tumulus 16 contained what Zürn calls a "charcoal floor" about 3cm thick and about 1.5m long, also on the ancient ground surface. This concentration of charcoal apparently did not contain any cremated bone. If all of the preceding assumptions are true, it seems probable that the central chamber is bi-ritual and could contain the remains of both an inhumation and a cremation grave. Bi-ritual graves are known from this period, and in fact Hohmichele Grave VII contained an inhumation and the remains of a cremated individual (Wahl in Kurz and Schiek n.d.). The complete excavation of Tumulus 17 will contribute to a resolution of this important issue.

Radiocarbon dating of several features was carried out by Beta Analytic Inc. of Miami, Florida. Charcoal samples recovered through water sieving and sorting from Features 1, 5, 9, 10, (all part of Stratum 5), as well as 15, and 16 were submitted for dating and yielded the following results:

The sample from Feature 9 may have been contaminated with debris from an animal burrow and contained some material that was only partially charred; this disturbance most likely accounts for the extreme deviation of its date from the dates of all other sampled features. The remaining five samples are so close in date that they independently support the interpretation of the mound as dating to the Hallstatt period. The average date is around 588 BC, corresponding closely to the presumed "founding" date of the Iron Age Heuneburg (Periods IVb/3 to Ia), which lasted from 600 BC-440 BC. The Hohmichele radiocarbon dates are very close to those from Tumulus 17 (Kurz and Schiek n.d.). The oldest of the Hohmichele dates is only 20 years older than the oldest date from Tumulus 17 (and given the standard deviation, that difference loses significance), while the most recent Hohmichele date is 20 years younger than the youngest of the dates from Tumulus 17.

The Period IV Heuneburg seems to have been occupied for only 70 years, from 600 BC until 530 BC, when the mudbrick wall settlement and its extra murus extension were destroyed by fire. That corresponds to roughly two generations (assuming a life expectancy of no more than 35 years), in which case the apparent overlap between Tumulus 17 and the Hohmichele is intriguing. It would seem worthwhile to obtain radiocarbon dates from the other mounds in the Hohmichele group, since the questions regarding what motivates the construction of a new mound and how mounds of different sizes relate to each other may be answered by a combination of aDNA analysis of individuals in these mounds (where possible) and their temporal relationships to one another. This second phase of the project is currently underway. The aDNA analysis is being conducted by Dr. Frederika Kaestle of Indiana University. The remaining quarters of Tumulus 17 were excavated in the summer of 2000. The results of that excavation and the accompanying aDNA analysis will be presented in follow-up reports.

We would like to thank the National Geographic Society, the National Endowment for the Humanities, the University of Wisconsin-Milwaukee Graduate School Research Fund, and the Landesdenkmalamt Baden-Württemberg, Außenstelle Tübingen for their generous financial support of this project. We would also like to thank the following individuals for their assistance and encouragement: H. Reim, S. Kurz, H. J. Teufel, S. Hopert, H. Hagmann, G. Jehle, A. Lumpp, H.W. Schäfer, and the citizens of Hundersingen, Mengen, and the Dollhof who made us welcome in their communities during our stay in 1999.

Bibliography

K. Bittel, W. Kimmig and S. Schiek, Die Kelten in Baden-Württemberg. 1981. Stuttgart: Konrad Theiss Verlag.
S. Kurz and S. Schiek (eds), Bestattungsplätze im Umfeld der Heuneburg. n.d. (September 30, 1997 version).
G. Riek, Der Hohmichele. 1962. Berlin:De Gruyter.
J. Wahl, Die menschlichen Knochenreste aus den Altgrabungen im Hohmichele. In Kurz and Schiek (eds), Bestattungsplätze im Umfeld der Heuneburg. n.d. (September 30, 1997 version).
H. Zürn, Grabhügel bei Böblingen. Fundberichte aus Baden-Württemberg 1979: 54ff.

Figures

Figure 1 Heiligkreuztal. Plan of the Hallstatt period Tumulus 17 in the Hohmichele-Group "Speckhau" showing the extent of the summer 1999 excavations. (Illustration: A. Chojnacki)

Figure 2.1 Partial profile (south profile) of the northeast quadrant showing stratigraphy and mound construction. (Illustration: A. Chojnacki)

Figure 2.2 Plan drawing #3 of the northeast quadrant showing stratigraphy and mound construction. (Illustration: A. Chojnacki)

Figure 3 Color photograph of the mound during excavation. Summer 1999. (Photo: S. Schneider)

A preliminary field report of the 1999 project was published in Archäologische Ausgrabungen in Baden-Württemberg 1999 under the following title: Untersuchungen an einem hallstattzeitlichen Grabhügel der Hohmichele-Gruppe im "Speckhau", Markung Heiligkreuztal, Gemeinde Altheim, Landkreis Biberach (Bettina Arnold, Matthew L. Murray, Seth A. Schneider), pp. 64-68.