Abstract: Where individual tides deposit appreciable accumulations of sediment, cyclic tidal rhythmites can form that exhibit semimonthly tidal cyclicities. A number of modern analogs and ancient counterparts indicate the importance of such features for paleoenvironmental analyses. In this study, predicted, high-low, tidal-station data are used to simulate current speeds, which in turn are used to simulate sedimentation of tidal rhythmites.

Abstract: The oldest known tidal rhythmites occur within the Big Cottonwood Formation, Utah, and are Late to Middle Proterozoic in age (800 Ma to 1.0 Ga). These rhythmites indicate that luni-solar tides were operating by this period of earth history. These rhythmites can be directly compared to modern analogs of rhythmite deposition such as those occurring in macrotidal estuarine and deltaic settings. In addition, the rhythmites bear many similarities to those commonly occurring in the Late Paleozoic of the U.S. Mid-continent.

Abstract:Incised valleys are an important, but little studied, component of Upper Pennsylvanian cyclothems in the Mid-Continent. During the Upper Pennsylvanian, glacio- eustatic cycles resulted in alternate exposure and flooding of vast areas of the Mid- Continent. Near equatorial paleolatitudes and extensive chemical weathering of the exposed craton resulted in mud-rich siliciclastic sediment influx to drainage networks that included incised valleys. During transgressions, incised valleys flooded to form tide- dominated, muddy estuaries. The Douglas Group (Virgilian) in eastern Kansas contains several incised valley fills (IVF) and a range of tidal facies that can be best understood through comparisons with modern deposits, mostly in macrotidal estuaries. Recognition of tidal influence in facies that are devoid of macrofossils is important for interpreting sea- level history, and lack of the recognition of tidal influence commonly lead to incorrect interpretations. Transitions from fluvial to estuarine facies, which were formed during marine flooding, can be recognized by the occurrence of mud-draped bedforms. Also the presence of facies that are likely the result of macrotidal conditions may have implications for paleogeographic reconstructions, because very high tidal ranges commonly occur in funnel-shaped estuaries. The IVFs occur throughout much of the Pennsylvanian in the Mid-Continent, and are probably even more common than previously has been recognized.

Several factors in addition to sea-level history influenced formation of IVFs. Climate may have had a profound influence. During wetter periods, rivers incised more deeply and developed extensive valley systems. During the drier periods, such as the Permian, valleys apparently did not develop at all. Other controls on valley morphology include bedrock lithologies exposed during incision, and basement structure.

Abstract: Within the U.S. Midcontinent, the lithologic succession of Kansas has provided stratigraphic information for a great variety of models of cyclic sedimentation, particularly cyclothems. Similar to most of the Pennsylvanian section of the midcontinent, the Douglas Group (Virgilian) represents a primarily siliciclastic interval that contains thin, laterally extensive carbonate marker beds.

The Douglas Group provides a particularly instructive sequence for the understanding of the interrelationships of carbonate and siliciclastic phases of deposition. Within this group, four unconformity bounded stratigraphic sequences can be delineated. The sequences include incised valleys filled with locally derived conglomerates and regionally derived sandstone and mudstone. These lowstand to transgressive system tracts are overlain by tidal estuarine facies and ultimately by marine carbonates, which characterize the late transgressive to highstand systems tracts. The limestones exhibit a number of shallow- water features including oolites, transgressive lags, and erosional bases. Some of the carbonates serve as widespread regional markers.

Although the Douglas Group sequences exhibit similarities to the classic "Illinois" and "Kansas" cyclothems, they are better understood when placed into a sequence- stratigraphic framework because genetic units are not the same as lithostratigraphic units. The balance between siliciclastic and carbonate deposition was determined by the varying rate of siliciclastic delivery to the coast, rate of sea-level change, and relative distance from shoreline. These factors, rather than water depths, exerted the dominant controls on the sequence-stratigraphic relationships.

Abstract: Laminated shales and heterolithic facies, which include lenticular, wavy, and flaser bedding, are common within Carboniferous coal measures of the Euramerican coal province. Such facies occur in France, Nova Scotia, eastern Kentucky, Indiana, Illinois, and Kansas. Sedimentologically, these rocks are characterized by laminae or ripple-scale bedforms. The majority of the facies are not well bioturbated but exhibit a distinct suite of superficial tracks and trails on laminae surfaces. Biogenic structures include a variety of arthropod tracks, fish-fin drag marks, and tetrapod trackways. Body fossils of either freshwater or marine forms are generally lacking except in rapidly formed concretions.

In general, such facies have traditionally been interpreted as the result of lacustrine and/or floodplain deposition in a fluvio-deltaic setting largely because of the lack of benthic marine fossils. Detailed sedimentological analyses of some of these sites, however, indicates a significant degree of tidal influence, which include development of cyclic tidal rhythmites and a specific assemblage of biogenic structures, both of which are similar to those forming in modern upper meso- to macrotidal estuaries.

Both lacustrine and tidal estuarine settings produce a variety of rhythmites. Lacustrine varves, distal turbidites, and tidal laminae are similar because all are produced by waning- flow processes. They are also all associated with rapid sedimentation so that surficial biogenic structures are commonly preserved. Although the presence of tidal cycles in laminae-thickness series offer strong evidence of tidal influences, their absence does not indicate a limnic origin. In areas with little accommodation space, daily tidal sedimentation may be amalgamated into non-cyclic rhythmites that are difficult to differentiate from non-tidal strata.

In addition, in modern, peat-forming tropical environments tidal effects can influence floodplain areas hundreds of kilometers inland. Recognition of these influences requires changes in analogs away from the traditional fluvio-deltaic to tide-affected coastal models. This change in analogs will profoundly influence Carboniferous paleoenvironmental reconstructions.

Abstract: This study compares Morrowan conglomeratic sandstones from three basins in the central North American craton: Central Appalachian Basin (eastern Kentucky), Eastern Interior Basin (Illinois, Indiana, western Kentucky, and lateral extensions in Arkansas), and Hugoton Embayment (Kansas and Colorado) to develop realistic analogues for Morrowan fluvial systems and to compare the relative effects of tectonic subsidence, eustacy, and paleoclimate on sedimentation.

Based upon paleogeographic reconstruction, the paleodrainage for the Central Appalachian Basin is estimated to have ranged from 1,337,100 sq km to 2,854,300 sq km, and for the Eastern Interior Basin from 1,568,600 sq km to 4,011,500 sq km. These sizes are comparable in scale to the modern Amazon River drainage area. Paleodrainage for the Hugoton Embayment was considerably smaller, estimated at 128,600 sq km to 282,900 sq km.

Comparing the varying effects of tectonic, eustatic, and paleoclimatic controls, the Central Appalachian Basin and Hugoton Embayment were particularly affected by ongoing regional tectonism, whereas the Eastern Interior Basin was affected to a much lesser extent. Eustatic changes influenced the development of sandstones, particularly within the Hugoton Embayment and the Eastern Interior Basin. Effects of climate were much more difficult to estimate, but the low-latitude position of the eastern basins had significant effects on the maturity of the sandstones and on the size of the fluvial systems. Degree of seasonality affected styles of fluvial sedimentation and paleosol development.

Abstract: Laminated to thin-bedded siltstones directly overlie Carboniferous coals at several localities in the Eastern Interior Coal Basin. Because lamina thicknesses show cyclical variations, the siltstones have been termed tidal rhythmites. They rhythmites commonly show a repetitive thick-thin pairing of the laminae, and these two-lamina rhythmites have been interpreted as the result of the asymmetry of flood and ebb velocities that affected sedimentation in a diurnal paleotidal systems. Alternatively, the pairing has been interpreted to be related to a pronounced difference in height between successive high tides in a semidiurnal system. This explanation suggests deposition in a mixed, predominately semidiurnal systems with a marked diurnal inequality. In addition to the two-lamina rhythmites described originally, subsequent examination of drill cores indicates the occurrence of relatively rare, more complex three- and four-lamina rhythmites.

A variety of mathematical techniques are used herein to analyze lamina-thickness data extracted from these rhythmites. Processing techniques include: (1) comparing the linear relationship between the thicknesses of the thinner and thicker laminae and comparing these relationships to modern tidal systems; (2) analyses of thickness periodicities and comparison with modern neap-spring tidal cycles; and (3) extraction of lamina-thickness inequalities and comparison to the diurnal inequalities that occur in semidiurnal tidal systems. These tests indicate that reasonable conclusions can be made for the type of originating paleotidal system. For the cases analyzed herein, the paleotidal signature suggests a mixed, predominantly semidiurnal system with a marked diurnal inequality.

Abstract: Lower Pennsylvanian paleovalley-confined sandstones are important petroleum reservoirs in the Midwest. In Kansas, such reservoirs have produced approximately 220 million bbl of oil and 1.7 tcf of gas. Valley-fill successions tend to become muddy upward, but there can be considerable local heterogeneity in which reservoir sandstones pass laterally into muddy sandstones or nonreservoir shales. The lack of understanding of this reservoir heterogeneity can lead to low drilling success rates. The Tonganoxie paleovalley (Upper Pennsylvanian, northeastern Kansas) contains facies very similar to Lower Pennsylvanian (Morrowan) valley fills, and can provide an outcrop- and subsurface-based model of sandstone deposition.

The Tonganoxie paleovalley was incised during lowered sea level and filled during the subsequent transgression. The main paleovalley is approximately 41 m deep, 11 km wide, and 240 km long, and was fed by 1-km-wide tributary valleys oriented roughly normal to the trunk valley. Sandstones occur in four distinct architectural elements that were deposited during different phases of transgression. Type I sandstone consists of a belt of sandstone and conglomerate 3-18 m thick and confined to the trunk valley and wider portions of tributary valleys. Type I sandstone consists of amalgamated channel fills, has little or no mud, and has the highest porosity and permeability. The type I sandstone is overlain by estuarine deposits of sandstone (type II sandstones), rippled argillaceous sandstone to sandy mudstone, and coal. Most of the paleovalley was filled during this stage. The type II sandstones are narrow (1.5 km wide) arcuate bodies up to 8 km long and were likely deposited in tidal point bars near the fluvial to tidal transition, are either isolated sandstones bodies or are incised into type I sandstone. The higher mud content is expected to reduce porosity and permeability compared to fluvial facies. Type III sandstone bodies occur at the upstream limits of narrow tributaries and are probably bay- head deltas. Well logs indicate a range of mud content. Type IV sandstone is a thin (3 m) discontinuous sheet of marine sandstone deposited after most of the paleovalley had been filled.

Abstract: The Hazel Patch sandstone is an informal unit of the lower Middle Pennsylvanian Breathitt Formation, which is locally dominated by facies containing 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, amalgamated rhythmites show partially or possibly cyclic trends that have been reworked or erosively truncated by overlying formsets, and noncyclic rhythmites show only random thickness distributions and no evidence or original cyclicity.

Lower in the sandstone, noncyclic rhythmites are associated with swaly to quasi-planar bedding, even bedding, and ripples with rounded crests, and are inferred to have formed in response to storm waves and combined flows. Higher in the sandstone, noncyclic, amalgamated, and cyclic rhythmites are present in association with herringbone stratification and pin-stripe laminae, and are inferred to have formed under the influence of tidal currents. Cyclic tidal rhythmites are 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. Upward and laterally within the channel, truncation of neap-cycle laminae by spring-cycle ripples, and a loss of continuous clay drapes in amalgamated rhythmites, led to preservation of only monthly or greater depositional cycles.

Vertical facies trends in the sandstones are interpreted to indicate upward shallowing from a wave-influenced outer estuarine or shallow shelf environment to an intertidal sand flat to an exposed low-lying coast upon which peats accumulated. The fact that cyclic rhythmites were preserved only in a shallow channel, stratigraphically near the middle of the units, may indicate that accommodation space and a medial estuarine position with little wave reworking and bioturbation controlled the preservation of the various orders of cycles.

Abstract: Recently, stacked successions of ancient tidal rhythmites have been found to preserve long records of tidal cycles. These include semidaily, daily, semimonthly, monthly, semiannual, annual and multiyear periods. Though such deposits reveal much about ancient tidal dynamics, the tidal signatures within the rhythmites can be masked or modified by basinal or nontidal effects. This paper discusses the results of an analysis of data from several different modern tidal stations. We show how actual tidal data can be abstracted to a form similar to what might ideally be preserved in the rock record, and then power spectra are calculated to yield estimates of the astronomical periods, which can be compared to the current values. In this study, data from four modern tidal stations, ranging from diurnal to semidiurnal, are analyzed as both time- and event-series. A series of tests, which involve selective removal of parts of the tidal signal, are made using the modern tidal-station data. These tests were performed in order to determine tow what extent the tidal signal can be degraded and still be recognized. Finally, we discuss some implications of the similarities of the modern and ancient tidal data and suggest how ancient data may be used to constrain basinal paleogeography and make inferences regarding ancient lunar orbital geometries.

Abstract: In the upper intertidal area of the Mont-Saint-Michel Bay estuary, the sediment consists of silty and sandy heterolithic facies which commonly display well- developed neap-spring cycles. Such facies have been termed tidal rhythmites because they exhibit rhythmicity directly related to tidal periodicities. The vertically accreted tidal bundles are related to flood-dominant deposition. They constitute a sedimentary record of a single semi-diurnal tidal cycle. The neap-spring cycle is reflected by a vertical evolution in the thicknesses of successive tidal bundles and types of bedforms. These neap-spring records range from a few cm to one dm in thickness and can be expressed in planar lamination, flaser to wavy bedding, and climbing-ripple bedding.

Tidal rhythmites are common in mid-continental Carboniferous sequences in the U.S. They are well developed in the Interior coal basins. Because such facies lack marine body fossils and contain few trace fossils, they have commonly been interpreted as non-marine. However, analyses of sequential series of laminae thickness indicate well-developed periodicities indicative of tidal influences during deposition. Modern analogues for such rhythmites have been described from upper reaches of estuarine systems such as the macrotidal Bay of Mont-Saint-Michel. Comparison of the Carboniferous tidal rhythmites with these modern analogues indicates many similarities, which extend to both physical and biogenic sedimentary structures.