I used to dig straight down at my local site in Tucson, now I read the dirt layers first
For two summers I just grabbed a trowel and dug until I hit something shiny at a site near Tucson, and I wrecked the context around a Hohokam sherd without even knowing it. Now I scrape one thin layer at a time and bag samples by depth, which takes way longer but I finally understand where things actually sit. A grad student showed me how a 2 cm level can change the whole story of a room. Anyone else switch methods after realizing they were digging blind?