Graphic LogsGraphic logs in the classroom A P 30 minBoards 1.8m long and 20cm wide are painted with a series of strata, e.g. 3 coal cyclothems, or interbedded breccias, dune sandstones and playa lake deposits.The rock types are shown using different colours and the sedimentary structures are drawn on. Students must measure each unit and make a graphic log from their data.