The Sediments of Dulung: Soil Chemistry and Weathering Profiles Date Stone Age Eastern India
Archaeologists in West Bengal's Dulung River Valley are using soil geochemistry and ferricrete stratigraphy to establish dates for Stone Age tools where acidic tropical soils destroy organic remains.
Rohan Bhattacharya for SwavedaOctober 17, 2026
In the humid tropical climate of eastern India, organic material rarely survives in the archaeological record. Bones, wood, and charcoal decay quickly in acidic soils, leaving prehistoric stone tools scattered across eroded landscapes without organic matter for radiocarbon dating.
Along the Dulung River valley in West Bengal—a tributary basin of the Subarnarekha—researchers are addressing this challenge by focusing on soil chemistry and weathering profiles rather than organic remains (ResearchGate). By analyzing the geochemical composition of ferricrete (iron-rich sedimentary crust) deposits and latosol (intensely weathered reddish soil) horizons, field archaeologists are establishing chronostratigraphic frameworks for prehistoric tool assemblages (Journal of the Anthropological Survey of India).
Iron Crusts and Weathered Horizons
Archaeological investigations in the Jhargram district have identified 28 prehistoric sites along the Dulung River drainage (Journal of the Anthropological Survey of India). The field surveys revealed a distinct stratigraphic pattern linking specific artifact types to particular geological horizons (ARF India).
Lower Palaeolithic assemblages, dominated by Acheulean handaxes (heavy bifacial stone tools), occur primarily embedded within thick ferricrete gravel deposits on elevated uplands (Journal of the Anthropological Survey of India). These ferricrete horizons formed during Pleistocene humid weathering cycles, where dissolved iron and manganese precipitated into hard crusts (ResearchGate). Tools cemented directly inside these indurated crusts were deposited before or during the formation of the ferricrete layers (ARF India).
In contrast, microlithic industries (small, finely worked stone blades and geometric tools) lie in younger latosol and oxisol (acidic, highly weathered red clay) soils in badland terrain (Journal of the Anthropological Survey of India). These distinct soil contexts demonstrate a clear chronological sequence: heavily weathered Acheulean implements belong to older, deeply oxidized ferruginous gravels, while fresh microlithic assemblages reside in later Holocene soil horizons (ResearchGate).
Geochemical Profiling as an Analytical Tool
In tropical landscapes where surface scatters are frequently redeposited by monsoon rain gullies, soil chemistry provides crucial contextual evidence (Journal of the Anthropological Survey of India). Geochemical analysis measures chemical weathering intensity across sedimentary profiles (Carleton College).
Researchers evaluate elements such as iron oxide, aluminum, and silica ratios within the matrix enclosing the tools (MDPI). Higher concentrations of iron and aluminum oxides, combined with the depletion of mobile alkali elements like sodium and calcium, indicate advanced chemical weathering under warm, humid palaeoclimatic conditions (MDPI).
Cross-referencing soil chemistry profiles with regional formations—such as the early-to-late Pleistocene Lalgarh Formation—allows researchers to determine whether artifacts lie in their original sedimentary context (in situ) or were transported by post-depositional erosion (Journal of the Anthropological Survey of India). Fresh-conditioned microliths found within upper latosols indicate minimal stream transport, whereas rolled and smoothed Lower Palaeolithic tools in exposed gravels reflect longer exposure to seasonal wash (Journal of the Anthropological Survey of India).
Regional Context in Eastern Indian Prehistory
The Dulung River valley findings align with broader prehistoric research across the Chota Nagpur Plateau and adjoining river basins, including the Subarnarekha and Burhabalang (ResearchGate). Field surveys documented in Man and Environment and reports from the Anthropological Survey of India have long noted the presence of Acheulean tool scatters embedded in lateritic deposits across eastern India (Journal of the Anthropological Survey of India).
Without preserved charcoal or fauna, absolute dating in these red-soil landscapes relies on physical methods like Optically Stimulated Luminescence (OSL)—which measures when quartz grains were last exposed to sunlight—alongside geochemical characterization of the surrounding sediments (ScholarSpace). OSL dating from comparable red-soil sites in eastern India, such as Mahadebbera and Kana, has established microlithic occupations dating back 42,000 to 25,000 years ago (ScholarSpace).
Establishing precise geochemical profiles for the sedimentary horizons of the Dulung River valley provides a systematic framework for dating surface scatters (Journal of the Anthropological Survey of India). Soil chemistry enables archaeologists to reconstruct environmental contexts, differentiate ancient occupational layers, and trace human settlement patterns across tropical South Asia (ARF India).