Tidal Bundles Research Articles

Reliability of lunar orbital periods extracted from ancient cyclic tidal rhythmites

Ancient tidal periods extracted from the geologic record are useful to constrain and calibrate theoretical models of the evolution of the earth-moon system. Analysis of rocks that contain such tidal periodicities, termed cyclic rhythmites, have tended to concentrate on long series and have focused on the more obvious periods. For example, neap-spring periods have been the most widely discussed; such information can be reliably extracted from bedform thickness series measured within laterally accreted tidal bundles and vertically accreted tidal laminae. Other lunar orbital data is also encoded in cyclic rhythmites; however this additional information has been much less extensively applied to earth-moon models. Herein, short segments of well-formed cyclic rhythmites are examined to determine how reliably the various tidal periods can be extracted via harmonic analysis. Rhythmite series analyzed here exhibit well-formed neap-spring tidal periods and also exhibit a prominent fortnightly inequality or a variation in the height of successive spring tides. This inequality is related to the elliptical nature of the lunar orbit (anomalistic month) and it is demonstrated that this period can also be reliably extracted from cyclic rhythmites. Tropical periods, which reflect the changing lunar declination that occurs during a tropical month, have also been reported from cyclic rhythmites. Unlike synodic and anomalistic periods, the apparent tropical periods extracted from some cyclic rhythmites do not always accurately correspond to the expected values. In only a few cases can this period be reliably extracted from short segments of cyclic tidal-rhythmite data. This period is commonly only poorly encoded in rhythmites because: (1) it tends to be masked by higher amplitude synodic periods, and (2) it is not well expressed within predominantly semidiurnal tidal systems. Samples selected from the Proterozoic and Phanerozoic tend to be more common during specific intervals of geologic time. These intervals were characterized by glacio-eustatic flux and, in some cases, by unique continental configurations. Understanding these basic controls on rhythmite occurrences should aid in the discovery of additional examples.

The Manciano Sandstone: a shoreface deposit of Miocene basins of the Northern Apennines, Italy

Well exposed, diamond-line cut, quarry-exposures of the Manciano Sandstone allow a detailed analysis of sandy, fossiliferous, nearshore deposits of the shelf of the Northern Apennines. The Manciano Sandstone is characterized by medium to very coarse, washed, fairly well sorted, lithic sandstone, with thin interlayers of sandy conglomerates. It displays two principal, rhythmically alternating sandy facies: (a) slightly burrowed (mostly Macaronichnus, Ophiomorpha, Skolithos) units, trough cross-bedded, locally showing possible tidal bundles with few whole Scutella (echinoid) shells reworked on foresets, or occasional large-scale (approximately 2 m) planar cross-bedded, bar-accretion units; and (b) slightly finer, darker-coloured reddish-brown sandstone units, heavily bioturbated ( Cruziana-Skolithos) ichnofauna) representing slightly more sheltered settings. Large oysters are present in near-living position in a few thin layers and, more commonly, as reworked, comminuted fragments in sandy layers. Many calcareous pebbles and oyster fragments are bored. Other fossils consist of echinoids ( Scutella), some balanids and reworked foraminifera and bryozoa. The Manciano sands were deposited primarily in a wave-dominated shoreface, containing migrating bars/ridges and affected by wave-induced, possibly tidal-enhanced currents. This tidal influence confirms the opening of the Miocene Apenninic Sea to oceans, both the developing Atlantic Ocean to the west and, through a long, narrow seaway, the Asian portion of the Tethys Sea to the east.

Facies analysis in the Lower Greensand using ground-penetrating radar

This paper presents the results of a ground-penetrating radar survey in the Woburn Sands Formation, Lower Greensand Group near Leighton Buzzard. A total of almost 4 km of survey has been acquired to investigate the internal structure of the sands. The radar survey achieved a resolution on the order of tens of centimetres with penetration up to 10 m and revealed a variety of horizontal, dipping and curved reflectors. The reflections are interpreted using seismic interpretation methodology. Two scales of unconformity-defined radar sequences are described. First-order radar sequence boundaries can be identified at the termination of primary reflectors. Second-order radar sequence boundaries can be identified at the terminations of both primary reflectors and first-order surfaces. First-order radar sequence boundaries are interpreted as reactivation surfaces within bedforms which are produced by changes in bedform geometry in response to a change in hydraulic regime or superimposed bedforms. Second-order surfaces are interpreted as the product of bedform migration. Reflection character and geometry are described and form the basis of a ground-penetrating radar facies analysis. Nine different radar facies have been identified. These are interpreted as large sets of planar cross-stratification, sets of trough cross-stratification, cosets of cross-stratification, tidal bundles, clay drapes, diagenetic concretions and possibly bioturbated sands. A reconstruction of the bedforms suggests that they were formed by very large curved crested dunes. These interpretations are checked against outcrop as the sands are excavated in working sand pits.

Tidal rhythmites infine-grained Carboniferous limestones, U.S.A.

Analyses of fine-grained limestones reveals that many exhibit fine-scale laminations. Laminations can be normally graded and consist of a coarser-grained lower part and a finer-grained upper part. The upper part can also contain finely disseminated organic material. Despite the similarities of such graded laminae to yearly varves and turbidites, it can be demonstrated by use of laminae-thickness periodicities that some graded laminae are reasonably interpreted as the product of tidal processes. Within siliciclastic systems, modern analogues of such processes are available for comparisons. In fine-grained facies of the Salem Limestone (Visean; Indiana, U.S.A.), periodicities observed within sequential-laminae thicknesses indicate a dominant control by neap-spring tidal processes. Similarly, laminae within limestones of the vertebrate-bearing Hamilton paleochannel (Stephanian; Kansas, U.S.) exhibit similar features, including fine-scale tidal bundles. This limestone is noted for the abundance of articulated fish fossils. Carbonates containing articulated fish from the Wild Cow Formation (Stephanian; New Mexico, U.S.), exhibit diffuse laminations; however, closely associated siliciclastic mudstones contain laminae that exhibit tidal periodicities. There are many similarities between tidal periodicities and patterns of lamination thicknesses of these rocks. A tidal interpretation for these rocks allows for localized, very rapid rates of deposition. Such rapid deposition may, in part, help to explain how articulated fish and other vertebrates can become preserved within such fine-grained limestones.

Evidence of seasonal precipitation in Pennsylvanian sediments of the Illinois basin

Pennsylvanian-age, small-scale tidal bundle sequences discovered on the eastern margin of the Illinois basin record years of continuous daily tidal deposition and have been used to interpret the astronomical factors influencing deposition. Because they also provide an absolute time scale of daily, monthly, semiyearly, and yearly resolution, these records can be used to identify nontidal factors of short duration. Deviations from the semiyearly and yearly sedmentation patterns predicted from pure tidal theory were observed in some of these tidal bundle sequences, and we interpret them to be the result of seasonal rainfall variations that affected sediment discharge. The possibility that seasonal climates existed in humid tropical paleoclimatic zones during the Pennsylvanian has been previously discussed, but analysis of the semi-yearly and yearly depositional patterns in tidal rhythmites of the Illinois basin provides direct evidence for their occurrence.

Tidal Flat Sedimentation and Event

The concepts of tidal bundle and spring-neap cycles put forward in the studiesof sedimentary structures of sand waves in tidal channels have recently been used intidal flat sedimentation out of tidal channel. In this note, the authors will usemicrosequence and small sequence to replace tidal couplet and spring-neap cycle, soas to see whether spring-neap cycle is applicable to open tidal flats of China.

Laterally and vertically accreted tidal deposits in the Upper Proterozoic Madina—Kouta Basin, southeastern Senegal, West Africa

The association of laterally and vertically accreted tidal deposits characterizes part of the Upper Proterozoic epicontinental deposits of the West African Platform. These deposits consist of symmetric thickening-up thinning-up, decimetre- to metre-thick, units bounded by centimetre-thick argillaceous layers containing mud cracks. Each unit comprises neap—spring tidal bundles in progradational cross-bedded sandstones bounded above and below by aggradational flat-bedded sand—silt alternations. The units are interpreted as deposits resulting from migration of subaqueous dunes (lateral accretion) over mud flats (vertical accretion) in an intertidal zone. The cyclic organization of the units, although imperfect because of preservation potential of strata, cannot be explained by the dune field migration alone. A periodic variation in the tidal environment, of unknown origin but of longer duration than neap—spring cycles, is suggested.

Evidence of tidal influences in Arnsbergian rhythmites in the Kincardine Basin

Synopsis Distinctive, vertically accreted rhythmitcs, in which evenly stratified bands of fine-grained silty sandstone alternate with much thinner bands of silty mudstone, overlie the thick marine mudstones above the Orchard and Calmy limestones in the Upper Limestone Group of the Kincardine Basin, east of Stirling. Each sandy band, together with the overlying mudstone band, is thought to represent a tidal bundle, with the sandstones being deposited during the more rapid stages of tidal flow and the mudstones during slack water. Successive sandstone bands are alternately thick and thin, reflecting dominant and subordinate tides, so that the mudstone bands are grouped into pairs. The rhythmites are similar to some Holocene vertically accreted tidal deposits, but more closely resemble Pennsylvanian tidal rhythmites in the Illinois Basin in which regular neap—spring—neap tidal cycles have been identified. Marine flooding was unusually widespread and deep during the major transgressions associated with the two limestones. This flooding may have produced wide, funnel-shaped inlets which amplified the tidal range, as well as ponding back rivers and consequently markedly reducing siliciclastic input into the basin. Tidal processes probably influenced British Carboniferous sedimentation more commonly than has hitherto been supposed.

Clastic Sedimentology of the Beaufort Formation, Prince Patrick Island, Canadian Arctic Islands: Late Tertiary Sandy Braided River Deposits With Woody Detritus Beds

The Beaufort Formation (probably of Pliocene age) exposed on Prince Patrick Island in the western Canadian Arctic Islands is an unlithified and poorly exposed unit consisting of the following assemblage of facies; (A) clast-supported gravel (channel floor lags, longitudinal bars); (B) cross-bedded sand (transverse bars, channel floor dunes); (C) rippled sand; (D) horizontally laminated fines - mixed sand, silt and woody detritus; (E) clay-rich mud (overbank suspension deposits); and (F) woody plant detritus, beds of flat-lying logs, sticks, twigs, wood chips, bark, leaves, needles, seeds, and moss (overbank suspension and traction deposits). Minor facies include pebble bands, plane laminated sand, and a thin bouldery basal gravel horizon. The sediments are interpreted to be sandy braided river deposits that are notable for their regionally abundant beds of course woody detritus, a feature uncommon in most ancient braided fluvial deposits. Facies A to C represent bar and channel deposits, with Facies B the most abundant. Facies C to F are relatively minor and are interpreted as low-stage overbank deposits such as abandoned channel fills. Rapid, small-scale lateral facies changes are the norm. Well-defined fining-upward sequences 1.2-2.5 m thick are uncommon. The relative rarity, thinness, and lateral impersistence of overbank facies compared to bar-channel facies suggests that significant amounts of meandering river deposits are not present. The common allochthonous woody fossils were sourced from boreal forests nearby. A thin horizon in one stratigraphic section contains tidal bundles with slack water mud drapes. The Beaufort sediments exposed on Prince Patrick Island appear to be the most proximal portion of a northwest-(offshore-) thickening clastic sheet. The eroded upper surface of the Beaufort Formation, of regional extent on the western arctic coastal plain, is covered with a highly polymict gravel lag that is far coarser and compositionally more diverse than gravel within the Beaufort Formation. Beaufort clasts and younger gravels (former glacial deposits?) appear to have been mixed together to form this residual lag, which at one site has been reworked into (glacio-?) fluvial gravel and sand filling a paleovalley.Key words: Beaufort Formation, Prince Patrick Island, sandy braided river deposits, allochthonous plant fossils, supra-Beaufort polymict lag

A tidal‐inlet complex in the Cretaceous epeiric sea of North America: Virgelle Member, Milk River Formation, southern Alberta, Canada

ABSTRACTThe upper portion of the Virgelle Member (Upper Cretaceous Milk River Formation) at Writing‐on‐Stone Provincial Park of southern Alberta preserves evidence of tidal processes along an otherwise wave‐dominated, progradational shoreline in the Cretaceous Interior Seaway of North America. The upper Virgelle Member is underlain by offshore transition to lower shoreface deposits of the Telegraph Creek Member and the lower Virgelle Member, respectively, and is overlain by the non‐marine shales and sandstones of the Deadhorse Coulee Member. The sediments of the upper Virgelle Member were deposited along a prograding shoreline and are interpreted here as those of a tidal‐inlet complex. Most inlet sections consist of an erosional base overlain by a shale‐pebble conglomerate, followed by cross‐bedded sandstones which become finer‐grained and decrease in scale upwards. Indicators of tidal processes include palaeocurrent distributions, mud couplets, tidal bundles, re‐activation surfaces and herringbone cross‐beds. The sequence through the tidal‐inlet complex can be differentiated, according to prevalent palaeoflow directions and sedimentary structures, as ebb‐dominated, flood‐dominated, or mixed‐tidal influence. Ebb‐dominated sections commonly contain lateral accretion surfaces whereas flood‐dominated sections contain tidal‐ramp deposits. Back‐barrier lagoon deposits are dominated by sandstones of an extensive flood‐tidal delta with only thin shales preserved locally at the top of the inlet complex. Deposits of ebb‐tidal deltas are absent, presumably due to the effective sediment dispersal by waves and wave‐induced longshore currents acting on the regionally wave‐dominated shoreline.

Viking Formation (Albian) at Eureka, Saskatchewan: A Transgressed and Degraded Shelf Sand Ridge (1)

The Viking oil field at Eureka is part of the long (80 km), narrow (10 km) east-west-trending Dodsland-Hoosier offshore sand ridge in west-central Saskatchewan. The various facies of the ridge are encased in marine mudstones, and the ridge has formerly been interpreted as a tidal current deposit. However, core examination shows that the facies are burrowed and bioturbated and very few primary sedimentary structures are preserved. The sandstone facies are extensively bioturbated by Teichichnus, and contain no medium-scale cross-bedding, and no other tidal features such as reactivation surfaces, spring-neap cycles and tidal bundles. Cross sections constructed from well logs and cores demonstrate that the ridge overlies an erosion surface, and that at least three other erosi n surfaces occur within the sand body. These surfaces strike east-west, and dip very gently southward. Pebble veneers occur in patches on the erosion surfaces. We interpret the ridge as having formed from a plume of sand in a shallow sea, with its western end close to a deltaic distributary channel (similar to the plume east of the modern Nile delta). The regional Viking shoreline moved north or northeastward into the basin during a lowstand of relative sea level. During subsequent transgression, the delta was eroded and displaced an unknown distance southwestward. The ridge also shifted southward, and was finally detached from the distributary and abandoned on the shelf. Original slopes of the southern ridge margin were flattened to gradients of 0.0006-0.0009 by storm-generated currents. The internal erosion surfaces were probably formed during the overall transgression. Rates of sediment movement were relatively slow, resulting in almost c mplete bioturbation and, hence, destruction of primary sedimentary structures.

Tidal inlet sequence, Sundance Formation (Upper Jurassic), north‐central Wyoming

ABSTRACTThe sandstones and coquinas of the upper 20 m of the Sundance Formation are interpreted as a tidal inlet, back‐barrier shoal and sandy tidal‐flat sequence deposited at the close of marine Jurassic sedimentation in north‐central Wyoming. The barrier strandline maintained a generally E‐W trend as it prograded to the north. The lateral migration of inter‐barrier tidal inlets along the regressive shoreline of the late Sundance sea caused the coquinas and sandstones of the uppermost Sundance Formation to be deposited as tabular, laterally‐extensive units. Tidal bundles, sigmoidal reactivation surfaces, herringbone cross‐lamination and abundant mud drapes within the sandstones are evidence of considerable tidal influence during the deposition of the uppermost Sundance Formation. Earlier models, which attach an offshore environment of deposition to the sequence, do not explain the tabular geometries of the sandstone and coquina units and their conformable stratigraphic relationship with the overlying non‐marine sediments of the Morrison Formation.

Tidal Bundles and Mud Couplets in the McMurray Formation, Northeastern Alberta, Canada: GEOLOGICAL NOTES

ABSTRACT Tidal bundles and mud couplets, recently found near the base of the McMurray Formation in the vicinity of Fort McMurray, northeastern Alberta, add further evidence to the interpretation that much of the Early Cretaceous deposition in that area was a result of tidal processes in a subtidal estuarine setting. Inference from comparative sedimentology suggests that sedimentation was influenced by a maximum paleo spring tidal range of 2 to 5 m, which is similar to that of modern estuaries in the Netherlands and Equador. DES BALLOTS DE MAREE (TIDAL BUNDLES) ET DES COUPLETS DE BOUE (MUD COUPLETS) DANS LA FORMATION MCMURRAY, NORD-EST DE L'ALBERTA, CANADA RESUME Des ballots de maree et des couplets de boue, trouves recemment pres de la base de la formation McMurray dans les environs de Fort McMurray, nord-est de l'Alberta, ajoutent a la preuve que la plupart des depots du Creface inferieur dans cette region sont interpretes comme etant le resultat de processus de maree dans un milieu estuarien a subtidal. L'etude de sediments semblables suggere que la paleosedimentation fut influencee par des hauteurs de marees de vives eaux allant de 2 a 5 m, semblables a celles d'estuaires modernes dans les Pays-Bas et en Equateur. Traduit par Marc Charest

The behaviour of intertidal sandwaves during neap‐spring tide cycles and the relevance for palaeoflow reconstructions

ABSTRACTVariations in migration distances and shape characteristics of sandwaves in relation to flow conditions were studied on the Ossenisse intertidal shoal in the Westerschelde estuary. The purpose was to analyse bedform behaviour, to establish the threshold and the time lags involved, to find differences in two‐ and three‐dimensional sandwaves and to determine the implications for palaeoflow reconstructions.Sandwave migration is well correlated with the peak depth‐averaged flow velocity of the dominant tide. Thus the latter parameter may be estimated from the thickness of the tidal bundles. Other flow parameters such as shear velocity, Chezy C or roughness length do not show a correlation with the migration and cannot be used in palaeoflow analysis.Flow depth does not correlate with sandwave height or with length. Consequently, neither sandwave height and length nor set height and length can be used for palaeoflow depth determination.Sandwaves start moving when the peak dominant flow velocity exceeds 0.5–0.6 m s−1, and appreciable changes in shape occur at 0.75–0.8 m s −1. Complete reversal of sandwaves is accomplished if both the dominant and subordinate peak depth‐averaged current velocities exceed 0.85 m s−1.Two‐ and 3‐D sandwaves appeared to have different stability fields in the velocity‐depth diagram and in the diagram of the Froude number versus the depth‐grain‐size ratio. In addition the distinction between 2‐D and 3‐D sandwaves appeared to be related to a variability in current direction during periods of appreciable sand transport. There are also differences in sedimentary structures between the two types of sandwaves.

Sigmoidal tidal bundles and other tide-generated sedimentary structures of the Curtis Formation, Utah

The Curtis Formation in central Utah contains a rich suite of sedimentary structures that provides persuasive evidence for a tidal mode of origin. The most diagnostic of these structures are sigmoidal tidal bundles: sandstone packages deposited during one dominant tidal episode that comprise a set of large-scale cross-lamination enclosed by two relatively gently dipping, sigmoid-shaped pause planes. Bundles are especially recognizable as tidally generated features because they exhibit an internal progression, from gentle, drape-like sigmoids to avalanche-type cross-bed foresets back to sigmoidal drapes. This progression reflects the sequential change in tidal flow velocities from slack water to maximum flow back to slack water. In addition, cyclic variability in the thickness and in internal structures among tidal bundles is clearly related to periodicity in the lunar month. These features of the Curtis Formation are remarkably similar to sedimentary structures observed in Holocene tidal sediments along the Dutch North Sea coast.

Depositional Environment and Geologic Age of Neogene Rocks at Cape Aliaksin, Beaver Bay, Alaska Peninsula: ABSTRACT

Neogene sandstone and conglomerate cropping out along the eastern end of Beaver Bay at Cape Aliaksin have been assigned to the Unga Conglomerate Member of the Bear Lake Formation. New data suggest that this correlation may be incorrect. The rocks at Cape Aliaksin consist of more than 250 m of interbedded sandstone and subordinate conglomerate overlain by volcanics. Sandstones are dominately cross-stratified tabular and sigmoidal beds. Paleocurrents are bimodal with a dominant north to south transport direction. Marine fossils are dispersed through the sandstones. Conglomerates are thin beds of cobble to boulder clasts. Some show southward imbrication; others are inversely graded. Fossils are rare in the conglomerates. The sandstones are interpreted as tidal sand waves and tidal bundles; conglomerates are interpreted as storm lag and debris flow deposits. The fossil assemblage includes gastropods, pelecypods, barnacles, and echinoids indicative of a shallow marine, cold-water biofacies. Taxa indicate End_Page 655------------------------------ a strong similarity to the fossil assemblage of the Tachilni Formation and the upper Bear Lake Formation, both assigned to the late Miocene Graysian Molluscan stage, approximately 12 Ma to 3 Ma. Teeth of the desmostylian (sea cow) Desmostylus sp. cf. D. hesperus have been collected from the Cape Aliaksin beds. D. hesperus is known from North Pacific rocks assigned to the late early to early late Miocene, approximately 18 Ma to 10 Ma. The Unga Conglomerate is in part typified by the middle Miocene pelecypod Mytilus gratacapi and an associated fauna unlike that of the Cape Aliaksin beds. It is suggested that the Cape Aliaksin beds are younger than the Unga Conglomerate, and are correlative to the upper Bear Lake Formation and Tachilni Formation rocks of early late Miocene age. End_of_Article - Last_Page 656------------

Sigmoidal Bundles and Other Tidal Features, Curtis Formation (Jurassic), Utah: ABSTRACT

Recently, a new suite of tide-generated sedimentary structures has been described, principally from sandy shoals and large excavations associated with flood-control structures in tidal estuaries of the Dutch coast. These sedimentary structures can be less ambiguous than criteria previously used to recognize tidalites. Structures and sequences of structures like those recognized in the North Sea can be applied to the rock record, in this case the Curtis Formation (Jurassic), San Rafael swell, Utah, to significantly enhance our ability to interpret tidal facies. Our discussion centers on the recognition of tidal bundles, the lateral succession of cross-strata generated by the migration of a large-scale bedform during one dominant tidal episode. Tidal bundles in the Curtis consist of two gently dipping sigmoid-shaped pause planes which enclose avalanche foresets. They are up to 80 cm (30 in.) thick and 11 m (36 ft) long. Pause planes may be accentuated by erosion of the megaripple by the subordinate tide, by generation of ripples or small megaripples with opposed inclinations, and/or by a drape of fine sediment which settles during slack water. Systematic variability that occurs within bundles is due to increasing then waning current velocity during a tidal episode. Systematic variability among tidal bundles results from regular fluctuations o tidal current velocities during a lunar month (neap/spring cycles). These include changes in bundle thickness, dip of foresets, internal geometry, and lateral extent. Recognition of these features in the Curtis leads to an uncontestable interpretation of its tidal origin. End_of_Article - Last_Page 497------------

Neap–spring tide sequences of intertidal shoal deposits in a mesotidal estuary

ABSTRACTIn the mesotidal (tidal range 3·5–4·9 m) Westerschelde estuary (The Netherlands) the intertidal part of a sandbank was the subject of systematic observations of: (1) hydrographic properties, (2) the distribution and response pattern of various types of bedforms, and (3) the sedimentary structures produced. Ebb and flood usually differ considerably in strength, giving rise to a clear dominance of one over the other, which may change over the neap‐spring tide period. Parallel, long‐crested sand‐waves and irregular, short‐crested dunes have a different response to the neap‐spring variation in current velocity.Because one tide (usually the flood in our area) predominated over the other, the internal structure largely consists of unidirectional cross‐bedding, separated into a succession of tidal bundles, each formed during one tide. The tidal bundles are arranged in a lateral sequence reflecting neap‐spring tide periods and differing in character with location.Within the tidal bundle, reactivation, full vortex and slackening structures reflect acceleration, full stage and deceleration of flow respectively in the dominant tide. The full vortex structures tend to be well developed around spring tide but disappear towards neap tide. The subordinate tide carves ‘pause planes’ which enclose the tidal bundles. These pause planes are either erosional or depositional (mud).