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McKenzie J A Davies PJ Palmer Julson A et al 1993 Proceedings of the Ocean Drilling Program Scientific Results Vol 133 15 SEDIMENTARY RHYTHMS AND CLIMATIC FORCING OF PLEISTOCENE HOLOCENE MIXED CARBONATE SILICICLASTIC SEDIMENTS OFF THE GREAT BARRIER REEF1 Craig R Glenn 2 Dick Kroon 3 and Wuchang Wei4 ABSTRACT Sediments recovered from the upper slope and outer shelf Great Barrier Reef transect Ocean Drilling Program Leg 133 Sites 819 through 821 contain a high resolution 1 5 m y record of mixed siliciclastic and carbonate sedimentation More than 30 multimeter scale couplets of fining and coarsening upward sediments having varying proportions of carbonate and authigenic glauconite are present These couplets stack into cyclic bundles observed in carbonate and magnetic susceptibility data that in turn vary systematically with respect to systems tract development deduced from sequence stratigraphic analysis At Site 821 these bundles and their variations clearly track relative changes in sea level for the past 1 48 m y The data presented suggest that these various levels of cyclicity are expressed as the result of high sedimentation rates along the margin and that the dominant control on their development has been climate variations that modulated variations in sea level and terrigenous influx The average duration of many of these cycles is in the Milankovitch waveband and is related to both fourth 102 443 ka and fifth order 34 88 ka cycles of sea level change These cycles are examined with respect to their lithology color percentage of total foraminifers bioclasts siliciclastics authigenic glauconite nannofossils and tunicates sequence stratigraphy downhole log characteristics magnetic susceptibility and percentage of carbonate Time series and Fourier transform results from high resolution magnetic susceptibility and sonic velocity data suggest strong orbital forcing of the sedimentary cycles although with differing intensities for different depositional packages and time

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