DISSOLUTION SEAMS - SOME OBSERVATIONS FROM THE PROTEROZOIC CHANDA LIMESTONE, ADILABAD, INDIA

The Proterozoic muddy carbonate turbidite beds in the Chanda Limestone , India are invariably differentiated gradationally into a lower seame d and an upper nonseamed layer. Inherited seamed and nonseamed layers within the autoclasts constituting the basal pebbly and bouldery mass- now deposits indicate preburial origin of the seams. Upward increase i n the thickness ratio between the intrabed seamed and nonseamed layers and general enlargement of the seams in the transgressive sequence pr eclude any correlation between seam generation and building of the sed iment overburden. Close delta(13)C delta(18)O values obtained from the seamed- and nonseamed-layer couplets also exclude difference in diage netic fluid composition as the cause for decoupling of every turbidite bed into layers of contrasting fabric. The paper lends support and su ggests tangible modification to Eder's (1982) model for depth-related differential dissolution of seafloor carbonates, and extends that to e xplain the origin of the bed-parallel pre-burial seams. Lack of biotur bation and Likely starvation of Precambrian deep carbonate basins shou ld have favoured generation and preservation of pre-burial dissolution seams.