The Site: Attirampakkam (13°13′50″N, 79°53′20″E, 38.35 m a.s.l), is an open-air Palaeolithic site situated near a meandering tributary stream of the river Kortallaiyar, northwest of Chennai, Tamil Nadu, along the southeast coast of India. Discovered in September 1863, by Robert Bruce Foote and his colleague William King, it was investigated in the early to mid 20th century by several scholars- T.T. Paterson, V.D.Krishnaswami and K.D.Banerjee. Later work on the prehistory of this region was conducted by A.Swami. S.Pappu's doctoral dissertation on the prehistory of the Kortallaiyar river basin (see publications), highlighted the importance of the context of artefacts at this site, in addition to other observations on the nature of the prehistoric record of this region.
Our Research Program: In 1999, our Centre initiated multidisciplinary research program in northern Tamil Nadu, with a focus on investigating questions related to the behavior of early populations in response to environmental changes within a sound chronological framework. Excavations: Excavations at Attirampakkam were initiated in 1999 to establish the stratigraphy and culture sequence, to obtain a secure chronology and to study the assemblages with a view towards investigating changing patterns in hominin behavior over the Pleistocene. Extensive gully erosion at Attirampakkam resulted in exposure of artefacts on the surface of the site over area of around 50,000 m2. A contour map of the site and surface deposits was prepared at 1 m intervals. Following this, test-pits, geological step trenches and horizontal trenches were excavated, with emphasis on meticulous recording of all artefacts and features sieving of all excavated sediments, and photography/videography. Samples were collected for sedimentological, palaeobotanical, micropalaeontological, and rock magnetic studies; and for geochronology.
Stratigraphy: These studies resulted in identification of eight major sedimentary horizons at the site. At the base of the sequence are argillaceous silty clays (Layers 6 and 8) interlayered with a gravel bed (Layer 7). The argillaceous silty clays also contain sandy, yellowish to red beds and laminations as well as quartzite pebbles (≤ 25 mm in length). In Layer 7, however, these well rounded quartzite clasts are larger (~40 mm), presumably washed out from pebble beds that occur within local sandstone strata in the Cretaceous bedrock. These layers form the horizon for the earliest Acheulian occupation at Attirampakkam. These deposits are overlain by a ferruginous gravel bed (Layer 5) capped by clay-rich silts (Layers 3 and 4), followed by fine-grained ferricrete gravels (Layer 2), and finally capped by an archaeologically sterile layer of clayey-silts (Layer 1) which also corresponds to the arable soil in neighbouring fields. This upper sequence (Layers 5 to 2) contains progressively younger, i.e., Late Acheulian and Early to Late Middle Palaeolithic assemblages. One of the most significant discoveries of this work was the presence of Acheulian artefacts within and underlying Layer 6, which had previously been classified as a Lower Cretaceous shale of the Avadi or Sriperumbudur series. Our research however indicated that these deposits were derived from eroding Cretaceous shale and sandstone outcrops in the catchment. These floodplain sediments aggraded during occupation, leading to repeated burial of artefacts discarded at the site.
We are able to reconstruct palaeomonsoons through studies of clay minerology and rock magnetics of the sediments, over the Early to Late Pleistocene. Three fossil faunal teeth Bovini, possibly representing Bubalus or Bos; Equus sp., Caprinae or Boselaphini) are from varied horizons, subject to bioturbation, and suggest an open and wet landscape, during phases in the Late Pleistocene. Possible animal footprints were noted at the contact horizon between Layers 5 and 6. Ongoing studies aim at reconstructing the palaeolandscapes around Attirampakkam, based on our ongoing regional surveys.
Chronology: Age estimates from horizons at Attirampakkam include palaeomagnetic, cosmogenic nuclide burial ages, OSL and ESR measurements. For Acheulian horizons of Layers 6 to 8, two different dating methods were employed. Artefacts from excavated trenches could be directly dated using cosmic ray exposure dating (26Al/10Be), applied for the first time at an archaeological site in India. Results indicated a minimum burial age estimate, with a weighted sample mean of 1.51 +/- 0.07 Ma. Palaeomagnetic measurements dated a 9 m profile of deposits within which Acheulian artefacts occurred. Results suggested that the sediment sequence was deposited before the normal Brunhes chron, i.e. before 0.78 Ma. Together with the cosmogenic burial ages and the nature of the Acheulian assemblage, the reversal was correlated with the Matuyama chron, and situated between the base of the Jaramillo (1.07 Ma) and top of the Olduvai (1.77 Ma) normal subchrons, neither of which are detected. These indicated that Acheulian hominins were present at Attirampakkam before 1.07 Ma. This suggests contemporaneity between Attirampakkam and some sites elsewhere in Africa and Israel with significant implications in terms of current debates on hominin dispersals across Asia.
Lithic Assemblages: Acheulian artefacts were on fine- to coarse-grained quartzites and are largely unabraded. Our ongoing studies of Acheulian lithics indicate complex reduction sequences based primarily on detachment of large flakes elsewhere in the region, which were then carried to the site and reduced further. The assemblage includes large cutting tools comprising bifaces (handaxes and cleavers) and other large flake tools, a small tool component, artefacts on cobbles, and waste flakes indicative of later stages in the reduction sequence. Studies of the Late Acheulian and Middle Palaeolithic assemblages are in progress. Our ongoing studies situate Attirampakkam as the oldest Acheulian site in India, dating back to around 1.5 Ma, (Early Pleistocene), with significant implications on estimating time frames of dispersals of hominins across Eurasia. The excavations resulted in new data on the context of Acheulian artefacts, which were found to occur in deposits which were previously thought to be Cretaceous in age, and which we now establish to be Early Pleistocene. Our studies have brought together multiple sciences in investigating palaeoenvironments.
Our research on lithic assemblages are in the process of highlighting differing reduction sequences, tool types and spatial patterning, with implications on Acheulian and Middle Palaeolithic hominin cognitive strategies.