The paper presents the results of a detailed study of the Early Proterozoic Akitkan and Trans-Siberian orogenic belts in the southern and central parts of the Siberian Craton. Each belt contains fragments of pre-accretionary rocks not associated with the evolution of orogenic belts. In the Akitkan belt, these are 2.88 and 2.15 Ga granitoids, as well as metamorphosed sedimentary rocks accumulated from 2.15 to 1.95 Ga. Pre-accretionary rocks in the Trans-Siberian orogenic belt include amphibole-biotite gneisses with the granitoid protolith age at 2.25 Ga, garnet-bearing paragneisses with the accumulation of terrigenous substrates at about 2.0 Ga, and, possibly, fragments of Archean rocks. Indicators of the formation of orogenic belts are igneous rocks, mainly granitoids of varying chemical composition aged 2.02–1.97 Ga, which could have been generated within accretionary orogens. Further evolution of the orogenic belts is related to the development of sedimentary basins in an extension setting, in which molassoid terrigenous rocks accumulated due to the destruction of the orogens, as well as to the intrusion of post-collisional igneous rocks in the time interval from 1.88 to 1.85 Ga. The formation of the Akitkan and Trans-Siberian orogenic belts followed the same scenario, and their evolution timeframe was quite extensive, from 2.02 to 1.85 Ga, which allows us to consider these Early Proterozoic orogenic belts as indicators of the formation of the Siberian Craton