Mapping buried ancient structure using gravity method: A case study from Cot Sidi Abdullah, North Aceh

Abstract

Samudra Pasai was an important area for trade, religion and political in Southeast Asia region for several centuries since the first millennium. The existence of the kingdom in the past is evident with the abundance of ancient graves and structures found along North Aceh coast. However, some of them are damaged or buried beneath the surface. We have applied gravity method to detect and delineate buried structure of Cot Sidi Abdullah, one of the remaining constructions of the Samudra Pasai Sultanate. Gravity method is a non-invasive geophysical technique that is proper for archaeological exploration. Foundation of Cot Sidi Abdullah structure is covered by a thick sandy layer, hence geometry of the building itself remains unknown. To delineate the suspected structure, gravity data were acquired on a 50 m by 30 m grid with station spacing of 2 m on the study area. The measured data were applied drift, latitude, free air, Bouguer, and terrain corrections. The residual complete Bouguer anomalies implied the presence of a possible man-made features. Horizontal derivative anomalies were used to delineate shape of the buried structure. Positive horizontal anomalies map shows that foundation of Cot Sidi Abdullah structure has rectangular shape and some detail small rectangular structures inside it. The map also shows some buried artefacts situated around the site.