Th/U and Ti/Al Ratios in Upper Ediacaran Phosphorite-Bearing Mudstones of the Lviv–Kishinev Depression and Moscow Syneclise in the East European Platform

Phosphorite-bearing mudstone beds in the lowermost part of the Kotlin regional stage (East European Platform) display average Th/U and Ti/Al values of 7.2 and 0.06, respectively. Such values are significantly higher than in the lower and uppermost parts of the sequence and the NASC and PAAS values. The erosion of mature source rocks during the deposition of phosphorite-bearing beds could lead to Th/U and Ti/Al values observed in the fine-grained sediments, suggesting the continental source of phosphorus.