A period of global uncertainty (Blank Spot) in the Precambrian history of the southern Siberian Craton and the problem of the transproterozoic supercontinent

Abstract

Two peaks of tectonomagmatic activity (1.90‐1.85 and 0.78‐0.74 Ga ago) are noted in the Precambrian history of the southern Siberian Craton. The first peak corresponds to the formation of the Siberian Craton [1]; the second peak, to rifting processes in the marginal zone of the craton at the stage of breakdown of Rodinia [2, 3], which completed by opening of the Paleoasian ocean. The time span between these peaks remains a blank spot in the geological history of the southern Siberian Craton. According to traditional views (see review in [4]), this period was characterized by continuous sedimentation at the craton margin (Fig. 1) with sporadic outbursts of volcanic activity recorded in sections of the Chaya, Medvezh’ya, and Khota formations and emplacement of subvolcanic intrusions (Chaya, Angaul, and Nersa dike complexes). However, the age of volcanic rocks and dike swarms, which could indirectly constrain the age of sedimentary rocks, remained indefinite. To fill this gap, we performed geochronological study of volcanic and dike complexes presumably corresponding [5, 6] to the aforementioned period of uncertainty (~1.9‐0.7 Ga). The results obtained would seemingly attract interest only for specifying regional stratigraphic schemes and chronology of igneous rocks. However, the new geochronological data taken together and their implications for chronostratigraphy of sedimentary sequences in the southern Siberian Craton yielded a surprisingly impressive result. At the very beginning, we would like to point out specially that areas insufficiently studied in terms of geochronology, e.g., the Baikal‐Patom Highland, have been omitted from our consideration. The Baikal and marginal uplifts of the Siberian Craton basement were the key targets of this study. The