RHYTHMIC SEDIMENTATION IN A MIXED TIDE AND WAVE DEPOSIT, HAZEL PATCH SANDSTONE (PENNSYLVANIAN), EASTERN KENTUCKY COAL FIELD

The Hazel Patch sandstone is an informal unit of the lower Middle Penn sylvanian Breathitt Formation, which is locally dominated by facies co ntaining alternating sand and shale layers, or rhythmic bedding. Three types of rhythmites are defined. Cyclic rhythmites show a sinusoidal vertical stacking trend of thickening and thinning laminae, amalgamate d rhythmites show partially or possibly cyclic trends that have been r eworked or erosively truncated by overlying formsets, and noncyclic rh ythmites show only random thickness distribution and no evidence of or iginal cyclicity. Lower in the sandstone, noncyclic rhythmites are ass ociated with swaly to quasi-planar bedding, even bedding, and ripples with rounded crests, and are inferred to have formed in response to st orm waves and combined flows. Higher in the sandstone, noncyclic, amal gamated, and cyclic rhythmites are present in association with herring bone stratification and pinstripe laminae, and are inferred to have fo rmed under the influence of tidal currents. Cyclic tidal rhythmites ar e present near the base of a shallow channel deposit. These rhythmites contain sandstone-shale couplets indicative of presumed diurnal tides , 11-12 laminae cycles indicative of neap-spring tidal sedimentation, and 25-27 laminae cycles indicative of lunar monthly sedimentation. Up ward and laterally within the channel, truncation of neap-cycle lamina e by spring-cycle ripples, and a loss of continuous clay drapes in ama lgamated rhythmites, led to preservation of only monthly or greater de positional cycles. Vertical facies trends in the sandstone are interpr eted to indicate upward shallowing from a wave-influenced outer estuar ine or shallow shelf environment to an intertidal sand flat to an expo sed low-lying coast upon which peats accumulated. The fact that cyclic rhythmites were preserved only in a shallow channel, stratigraphicall y near the middle of the unit, may indicate that accommodation space a nd a medial estuarine position with little wave reworking and bioturba tion controlled the preservation of the various orders of cycles.