Abstract

The 300 m thick upper Precambrian Elisabeth Bjerg Formation in East Greenland represents a period of intermittent siliciclastic-dominated marine deposition on a carbonate ramp. Four depositional systems are identified within the exposed formation: (1) a siliciclastic ramp system formed by prograding shoreface or delta complexes; (2) a carbonate outer-ramp system comprising rhythmically interbedded carbonate mudstone, subtidal stromatolitic biostromes, calcarenite deposits, and siliciclastic mudstone; (3) a transitional siliciclastic-carbonate system consisting of 0.3-0.6 m thick subtidal rhythmites, created by carbonate mudstone and conglomerates alternating with siliciclastic mudstone; and (4) a carbonate inner-ramp system consisting of intertidal and subtidal channel deposits. On the basis of stacking patterns within the depositional systems, lowstand, transgressive, and highstand systems tracts can be inferred, which are traceable across the entire outcrop area, more than 200 km along and 100 km perpendicular to basin strike. The systems tracts combine to form five 30-100 m thick sequences within the Elisabeth Bjerg Formation and two that extend into the surrounding formations. All of the sequences show the same basic internal architecture, most likely developed in response to third-order glacio-eustatic changes in sea level. The paleogeographic evolution, and the response of the four depositional systems to cyclic changes in sea level, are interpreted using a ramp-to-basin model. During lowstands, sedimentation was dominated by siliciclastic deposition. Stranded lowstand shoreline deposits were formed in the more distal part of the ramp, while the inner part of the ramp was a zone of sediment bypass. During subsequent relative sealevel rise the ramp was flooded and starved of sediment. Early highstands were characterized by carbonate deposition, including the formation of large stromatolite buildups, while siliciclastic deposition was confined to a narrow near-coastal zone. During late highstands decreasing accommodation space resulted in progradation of the siliciclastic deposits, forcing carbonate deposition basinward.

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