John of Ephesus
Jacob Baradaeus, who had become Bishop of Edessa, consecrated Sergius as patriarch of Antioch at Constantinople, thus cementing the schism in the church of Antioch into the non-Chalcedonian Syriac Orthodox Church and Chalcedonian Imperial Church. Sources disagree on the date of Sergius' consecration as patriarch. According to the "Zuqnin Chronicle", he was consecrated in 544, whereas John of Ephesus in his "Ecclesiastical History" dates the consecration to 557. Sergius resided at Constantinople for the duration of his term as patriarch, for which he was later erroneously termed patriarch of Constantinople by the 14th-century historian Nikephoros Kallistos Xanthopoulos in his "Ecclesiastical History". He died a natural death, either in 547 as per the Zuqnin Chronicle, or in 560 as per John of Ephesus.