The Mortar of Arikamedu: How Chemical Analysis of Roman Amphora Residues Redefines the Coromandel Wine Trade

For decades, the story of Indo-Roman maritime trade along the Coromandel coast rested on physical shapes. Archaeologists classified transport jars by their handles, rims, and clay colors to trace the movement of goods between the Mediterranean and the Bay of Bengal.

At Arikamedu—the Sangam-era port site situated four kilometers south of Puducherry along the Ariyankuppam River—excavations led by Robert Eric Mortimer Wheeler in 1945 and later by Vimala Begley uncovered hundreds of Mediterranean ceramic fragments. These included double-handled Dressel 2–4 amphorae, a type widely used across the Early Roman Empire.

Morphology alone, however, leaves a crucial gap. A Mediterranean jar found in South India might have been filled in Italy, emptied in Egypt, refilled with local wine or oil, and shipped eastward by Middle Eastern intermediaries. Without testing the organic compounds absorbed into the porous ceramic walls, scholars debated whether Arikamedu operated as a destination for direct Roman bulk cargoes or merely as a secondary distribution hub handling re-packaged local goods.

Recent archaeometric investigations employing gas chromatography-mass spectrometry (GC-MS) on amphora sherds recovered from Early Historic layers at Arikamedu provide definitive chemical evidence. The laboratory analysis reveals distinct molecular biomarkers embedded inside the unglazed ceramic matrices, fundamentally clarifying the nature of the Coromandel wine and oil trade.

Molecular Fingerprints in the Clay

To understand what these transport jars contained, chemical analysts evaluate two primary types of organic markers: tartaric acid derivatives and diterpenic resin compounds.

Tartaric acid serves as the primary biomarker for grape-based products, as few other plants produce it in significant concentrations. Gas chromatography-mass spectrometry of the interior fabric of the Arikamedu Dressel 2–4 sherds identified tartaric acid alongside malic acid, confirming that the vessels originally held fermented grape wine rather than grain beers or regional palm spirits.

The chemical profile also revealed high concentrations of methyl dehydroabietate and retene. These compounds are degradation products of Pinaceae pitch—pine resin. Roman winemakers routinely lined the porous interior walls of ceramic transport jars with heated pine pitch to waterproof the terracotta and flavor the contents. The co-occurrence of tartaric acid and diterpenic pine resin within the same ceramic layer demonstrates that the wine was pitch-sealed inside these specific Mediterranean vessels at its original point of production.

Additionally, organic residue testing on select wide-mouthed amphora sherds yielded long-chain fatty acids and triacylglycerol degradation profiles indicative of plant oils. The specific ratios of oleic, palmitic, and stearic acids match Mediterranean olive oil signatures rather than regional tropical seed oils.

Because pitch waterproofing degrades when exposed to olive oil, Roman potteries rarely lined oil amphorae with resin. The absence of pine resin markers in the oil-bearing sherds aligns with known Roman industrial standards, ruling out accidental contamination or later reuse for local liquids.

Anchoring the Timeline to Early Imperial Exports

These chemical findings directly tie the chronology of the Coromandel coast to early Roman Imperial economic policy.

The primary ceramic forms identified at Arikamedu—specifically Dressel 2–4 wine amphorae—were produced predominantly between the late first century BCE and the late first century CE. This matches the historical window documented in the Periplus Maris Erythraei (Periplus of the Erythraean Sea), a first-century CE Greek navigational log that explicitly names the port of Poduke (Poduca)—identified by scholars as Arikamedu—as a major emporium for imported Western wine.

Evidence shows that the Roman state expanded its export capacity during the Julio-Claudian period (27 BCE–68 CE). The presence of unadulterated Italian and Tyrrhenian resinated wines at Arikamedu demonstrates that merchant vessels departing Red Sea ports like Myos Hormos and Berenike carried long-distance bulk liquids straight across the Indian Ocean during the Southwest Monsoon.

This direct material evidence complicates the interpretation of local numismatic patterns. While Roman silver denarii and gold aurei are remarkably sparse in coastal excavated trenches at Arikamedu, large hoards—such as the 1,408 denarii found at Budinatham in western Tamil Nadu—are concentrated at inland sites like Karur.

Scholars debate why gold and silver specie accumulated in interior river valleys while bulk ceramic goods remained concentrated along the coast. The residue analysis proves that wine and oil arrived intact in foreign containers, suggesting that coastal ports like Poduke acted as immediate discharge points for heavy liquid cargoes, which were consumed or exchanged locally, while precious metal coins traveled westward along inland trade routes toward political capitals.

By replacing stylistic assumptions with chemical verification, gas chromatography-mass spectrometry grounds the study of ancient Indian Ocean commerce in physical proof. The pitch and tartaric acid locked inside Arikamedu's clay sherds offer clear evidence of direct, un-repackaged shipments connecting Mediterranean vineyards straight to the Coromandel shore.