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Marine transgression and regression in Miocene sequences of northern Pegu (Bago) Yoma, Central Myanmar
- Neogene strata of the northern part of the Pegu (Bago) Yoma Range, Cent ral Myanmar , con ta in a series of shallow marine clastic sediments with stratigraphic ages ranging from the Earl y to Late Miocene. The studied succession (around 750 m thick ) is composed of three major stratigraphic unit s deposit ed during a major regression and four major transgressive cycles in the Early to Late Miocene. The transgressive deposit s consist of elongate sand-bars and broad sand-sheets that pass headward into mixedflats of tidal environments. Marine floodin g in transgressive deposits is associated with coquina beds and allochthonous coralbearing sandy limestone bands. Major marine regressions are associated with lowstand progradation of thick estuary point-bars passing up into upper sand-flat sand bodies encased within the tidal flat sequences and lower shoreface deposits with local unconformities. The succession initially formed in a large scale incised-valley system, and was later interrupted by two major marine transgressions in the generally regressive or basinward-stepping stratigraphic sequences. Successive sandbo dies were formed during a sea-level low stand and early stage of the subsequent relative rise of sea level in a tide-d ominated estu ary system in the eastern part of the Central Myanmar Tertiary Basin during Early to Late Miocene times. © 1999 Elsevier Science Ltd . All rights reserved.