He chose to excavate there, based on the previous work of Dr. M.H. Krishna, hoping that it would show a long depth of chronology, as well as allow some connection between the ceramic sequence/chronology with the Asokan rock edicts, and the Russet Coated Painted Ware, or Andhra Ware, already cross dated with roman coins to the first centuries AD at Arikamedu (Wheeler 1946; Casal 1949; Begley 1996).
Since the site was dug long before radiocarbon dating, or any other method of secure absolute chronology, Wheeler presumed that the known date of the edicts would help him date the rest of the occupation. Though he managed to associate the rock edict with the black-and-red ware in the megalithic burials, and the same black-and-red ware in the habitation area, he vastly underestimated the amount of time that was represented by this ceramic type.
Recent re-analysis by Dr. Kathleen Morrison has shown that the site's chronology is indeed very deep, and that much of Wheeler's analysis of the ceramic sequence turns out to be problematic (Morrison 2005). Despite the early work done at Brahmagiri, it's prominence in archaeological writings on South India, and the recent work by Dr. Morrison, much research remains to be done.
For the full set of pictures go here.
Begley, V. (1996) Ancient Port of Arikamedu: New Excavations and Researches 1989-1992. École Française D'Extreme-Orient, Pondicherry.
Casal, J. M. (1949) Fouilles de Virampatnam-Arikamedu. Imprimerie Nationale, Paris.
Morrison, K. D. (2005) Brahamagiri Revisited: a Re-analysis of the South Indian Sequence. In South Asian Archaeology 2001, edited by C. Jarrige, & V. Lefèvre, Editions Recherche sur les Civilisations ADPF, Paris.
Wheeler, R. E. M., Ghosh, M. A., & Deva, K. (1946) Arikamedu - An Indo-Roman trading station on the east coast of India. Ancient India, 2: 17-124.
Wheeler, R. E. M. (1948) Brahmagiri and Chandravalli 1947: Megalithic and Other Cultures in the Chitaldrug District, Mysore State. Ancient India, 4: 181-310.