In Eastern Transbaikalia, the Lower Jurassic (uppermost Pliensbachian(?) to Toarcian) deposits exposed on the right bank of the Borzya river near the village of Onon-Borzya have been studied in detail. These deposits with a total thickness of more than 100 m are well exposed in a 3-4 m high and 351 m long cliff and are composed of clayey and sandy siltstones. Ten lithological members were described for the section: members 1-3 are correlated with the Pliensbachian-Toarcian boundary strata of Siberia (uppermost Sharapovo to Kiterbyut horizons), whereas members 4-10 are correlated with the Toarcian strata of the Nadoyakh horizon of Siberia. Macrofossils (ammonites, belemnites, bivalves, gastropods, brachiopods), especially bivalves, are rather common and have been identified by us. Among belemnites, we introduce the first records of several genera in Eastern Transbaikalia.