Pockets of Ediacaran–Cambrian clastic sedimentary rocks are preserved across Fennoscandia, but the provenance, depositional setting and age of many such deposits remain uncertain. We report the first detrital zircon provenance study of the lowermost sediments deposited on sub-Cambrian bedrock in southern Sweden. We performed 285 ion microprobe U–Pb analyses on zircons from the Mickwitzia Sandstone (File Haidar Formation, Cambrian Series 2). Age peaks at c. 2100, 2000, 1800, 1550, 1500, 1225, 1150 and 950 Ma are consistent with Sveconorwegian and Fennoscandian source rocks, whereas a major peak at c. 550 Ma is attributed to the Timanian orogen to the NE. The youngest dates in the dataset, including multiple consistent dates from single grains, indicate a maximum depositional age of c. 550 Ma. This first documentation of Timanian-aged grains in southern Sweden connects reports of Timanian detritus as far afield as northern Norway, Estonia and even Poland. The Timanian detrital signature across thousands of square kilometres suggests that much of Baltica probably consisted of an extremely low-relief plain over which Timanian-sourced detritus spread extensively during the late Ediacaran and early Cambrian.