Which archaeologist specifically paid attention to the stratigraphy of the mound while excavating the Harappan sites?

Wheeler

Marshall excavated using regular horizontal units, measured uniformly throughout the mound. However, this approach ignored the stratigraphy of the site, resulting in the loss of valuable contextual information about the artifacts.
R.E.M. Wheeler, who became Director-General of the ASI in 1944, recognized the need to follow the stratigraphy of the mound instead of uniform horizontal lines. He brought military precision to the practice of archaeology, rectifying the shortcomings of Marshall's approach.
Overall, the discovery of seals and the announcement of a new civilization during Marshall's tenure marked significant advancements in Indian archaeology. However, it was Wheeler who addressed the issue of stratigraphy and introduced a more precise approach to excavation.