Erik P. Kvale

Daily, monthly, and yearly tidal cycles within laminated siltstones of the Mansfield Formation (Pennsylvanian) of Indiana

Whetstones (laminated siltstones) within the Mansfield Formation of Orange County, Indiana, are Lower Pennsylvanian (Morrowan) tidal deposits characterized by rhythmic laminations. Laminae thicknesses vary systematically in a vertical sequence and reflect tidal events of a mixed tidal regime. So complete is the record of tidal deposition that daily and monthly tidal cycles can be delineated. Neap-spring tides (related to the phases of the moon) and equatorial-tropical tides (related to the declination of the moon) are recognizable within the sequence.

Late Proterozoic and Paleozoic Tides, Retreat of the Moon, and Rotation of the Earth

The tidal rhythmites in the Proterozoic Big Cottonwood Formation (Utah, United States), the Neoproterozoic Elatina Formation of the Flinders Range (southern Australia), and the Lower Pennsylvanian Pottsville Formation (Alabama, United States) and Mansfield Formation (Indiana, United States) indicate that the rate of retreat of the lunar orbit is dξ/dt ∼ k2 sin(2δ) (where ξ is the Earth-moon radius vector, k2 is the tidal Love number, and δ is the tidal lag angle) and that this rate has been approximately constant since the late Precambrian. When the contribution to tidal friction from the sun is taken into account, these data imply that the length of the terrestrial day 900 million years ago was ∼18 hours.

Late Albian Kiowa-Skull Creek Marine Transgression, Lower Dakota Formation, Eastern Margin of Western Interior Seaway, U.S.A.

ABSTRACT An integrated geochemical-sedimentological project is studying the paleoclimatic and paleogeographic characteristics of the mid-Cretaceous greenhouse world of western North America. A critical part of this project, required to establish a temporal framework, is a stratigraphic study of depositional relationships between the Albian-Cenomanian Dakota and the Upper Albian Kiowa formations of the eastern margin of the Western Interior Seaway (WIS). Palynostratigraphic and sedimentologic analyses provide criteria for the Dakota Formation to be divided into three sedimentary sequences bounded by unconformities (D0, D1, and D2) that are recognized from western Iowa to westernmost Kansas. The lowest of these sequences, defined by unconformities D0 and D1, is entirely Upper Albian, and includes the largely nonmarine basal Dakota (lower part of the Nishnabotna Member) strata in western Iowa and eastern Nebraska and the marine Kiowa Formation to the southwest in Kansas. The gravel-rich fluvial deposits of the basal part of the Nishnabotna Member of the Dakota Formation correlate with transgressive marine shales of the Kiowa Formation. This is a critical relationship to establish because of the need to correlate between marine and nonmarine strata that contain both geochronologic and paleoclimatic proxy data. The basal gravel facies (up to 40 m thick in western Iowa) aggraded in incised valleys during the Late Albian Kiowa-Skull Creek marine transgression. In southeastern Nebraska, basal gravels intertongue with carbonaceous mudrocks that contain diverse assemblages of Late Albian palynomorphs, including marine dinoflagellates and acritarchs. This palynomorph assemblage is characterized by occurrences of palynomorph taxa not known to range above the Albian Kiowa-Skull Creek depositional cycle elsewhere in the Western Interior, and correlates to the lowest of four generalized palynostratographic units that are comparable to other palynological sequences elsewhere in North America. Tidal rhythmites in mudrocks at the Ash Grove Cement Quarry in Louisville (Cass County), Nebraska record well-developed diurnal and semimonthly tidal cycles, and moderately well developed semiannual cycles. These tidal rhythmites are interpreted to have accumulated during rising sea level at the head of a paleoestuary that experienced at least occasional mesotidal conditions. This scenario places the gravel-bearing lower part of the Nishnabotna Member of the Dakota Formation in the mouth of an incised valley of an Upper Albian transgressive systems tract deposited along a tidally influenced coast. Furthermore, it provides a depositional setting consistent with the biostratigraphic correlation of the lower part of the Nishnabotna Member of the Dakota Formation to the marine Kiowa Formation of Kansas.

Oldest direct evidence of lunar-solar tidal forcing encoded in sedimentary rhythmites, Proterozoic Big Cottonwood Formation, central Utah

The oldest known tidal rhythmites, identified in the Big Cottonwood Formation, Utah, are Late to Middle Proterozoic in age (800 Ma to 1.0 Ga), ∼250 to 400 m.y. older than the previously oldest known tidal rhythmites. Four tidally forced cycles and one nontidal (seasonal) cycle control lamina thickness patterns. All of these cycles are recognized in outcrop and core and include cycles associated with daily, semimonthly (synodic), monthly (anomalistic), semiyearly, and yearly (seasonal) events. These features form the oldest geological record of lunar-solar tidal forcing and show that the middle to late Precambrian lunar- and solar-generated tides behaved in a manner very similar to that of today. The analysis also suggests that the Big Cottonwood Formation may have undergone a seasonal climate.

Tidal deposits associated with low-sulfur coals, Brazil Fm. (Lower Pennsylvanian), Indiana

ABSTRACT The interval between the Lower and Upper Block Coal Members of the Brazil Formation (Lower Pennsylvanian, Indiana) records a transgression of brackish water tidal deposits over a coastal domed(?)-peat field, followed by a regression, and then re-establishment of the peat-forming environment. Within the study area, the interval averages 8 m in thickness and consists of a basal sequence of laminated mudstone that coarsens upwards to thinly interlayered sandstone and mudstone (lenticular, wavy, and flaser bedding). This is capped by an upward-fining sequence into a rooted mudstone. Sedimentation rates can be estimated by derailed thickness measurements of vertically stacked mudstone laminae and sandstone layers that thicken and thin rhythmically. This rhythmic thickness variation can be elated to neap-spring tidal-current cyclicity and indicates that sedimentation varied from 1 cm/yr to 1 m/yr. Locally, as much as 8 m of accommodation space for the sediments appears to have been generated and mostly filled in a matter of decades to a few centuries. Such rapid rates of filling indicate the possibility that the accommodation space was generated by compaction of the transgressed peat and mud-rich sediments.

Comparison of drier- to wetter-interval estuarine roof facies in the Eastern and Western Interior coal basins, USA

Abstract Many of the Carboniferous coals in the eastern interior of the US are associated with siliciclastic roof facies that were deposited within a fluvio-estuarine transition. These facies include a variety of rhythmites, some of which exhibit tidal cycles. Drier-interval coals (Westphalian B-C, Stephanian) tend to be more laterally restricted and more commonly are associated with paleovalleys. Conversely, wetter-interval coals (Westphalian D) are very widespread and are not restricted to paleovalleys. Throughout the Lake Carboniferous, wet paleoclimates associated with these coals lead to valley incision during sea-level lowstand when large tropical rivers downcut older sediments deposited during previous sea-level highstands. During subsequent rise of sea level, these fluvial valleys were flooded and converted to estuaries where tidal ranges and sedimentation rates were significantly amplified. Based on modern analogs and interpretation of many examples of Carboniferous tidal rhythmites, the localized depositional rates in these settings are exceptionally high. The estuaries became sediment sinks, trapping sediment that is pumped in from both fluvial and marine sources. As a result, sedimentation readily keeps pace with rising baselevel. Extensive intertidal flats and shallow subtidal flats are created and prograde over the valley-confined mires. Thick tidal cycles and upright trees (some with attached foliage) record rapid burial of mires. This model is supported with examples of roof facies from the Westphalian B-C of the Eastern Interior Basin, and the Stephanian of the Western Interior Basin. In these areas facies within each cycle range from well-developed, extensive paleosols and coals, to widespread marine shales or limestones. Variations in both sea level and climate resulted in a complex history of valley fill during which coals could be developed at any time (except during widespread flooding). Minable, low-sulfur and low-ash coals occur, but the coals are relatively thin and discontinuous. Conversely, the Westphalian D coals are very widespread and significant peat accumulations were not confined to paleovalleys. Nonetheless, the lowest sulfur coals are related to rapid deposition of roof facies that occurred within the paleovalley whereas high-sulfur coals were formed in areas of lower sedimentation rate of roof facies that occurred beyond the confines of the paleovalley.

Middle Jurassic (Bajocian and Bathonian) Dinosaur Megatracksites, Bighorn Basin, Wyoming, U.S.A

Abstract Two previously unknown rare Middle Jurassic dinosaur megatracksites are reported from the Bighorn Basin of northern Wyoming in the Western Interior of the United States. These trace fossils occur in carbonate units once thought to be totally marine in origin, and constitute the two most extensive Middle Jurassic dinosaur tracksites currently known in North America. The youngest of these occurs primarily along a single horizon at or near the top of the “basal member” of the “lower” Sundance Formation, is mid-Bathonian in age, and dates to ∼167 ma. This discovery necessitates a major change in the paleogeographic reconstructions for Wyoming for this period. The older tracksites occur at multiple horizons within a 1 m interval in the middle part of the Gypsum Spring Formation. This interval is uppermost Bajocian in age and dates to ∼170 ma. Terrestrial tracks found, to date, have been all bipedal tridactyl dinosaur prints. At least some of these prints can be attributed to theropods. Possible swim tracks of bipedal dinosaurs are also present in the Gypsum Spring Formation. Digitigrade prints dominate the Sundance trackways, with both plantigrade and digitigrade prints being preserved in the Gypsum Spring trackways. The Sundance track-bearing surface locally covers 7.5 square kilometers in the vicinity of Shell, Wyoming. Other tracks occur apparently on the same horizon approximately 25 kilometers to the west, north of the town of Greybull. The Gypsum Spring megatracksite is locally preserved across the same 25 kilometer east-west expanse, with the Gypsum Spring megatracksite more extensive in a north-south direction with tracks occurring locally across a 100 kilometer extent. Conservative estimates for the trackway density based on regional mapping in the Sundance tracksite discovery area near Shell suggests that over 150,000 in situ tracks may be preserved per square kilometer in the Sundance Formation in this area. Comparable estimates have not been made for other areas. Similarities between the two megatracksites include their formation and preservation in upper intertidal to supratidal sediments deposited under at least seasonally arid conditions. Microbial mat growth on the ancient tidal flats apparently initiated the preservation of these prints.

Analysis of modern tides and implications for ancient tidalites

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 to 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 paleography and make inferences regarding ancient lunar orbital geometries.

A tidal model of Carboniferous Konservat-Lagerstaetten formation

Rapid deposition of laminated sediments in tidally influenced estuaries can explain many characteristics of some Carboniferous Konservat-Lagerstatten. In modern environments each tide can potentially deposit a layer of normally graded mud. Localized depositional rates as high as 1 cm or more of sediment per week can occur in tidal estuarine settings. Characteristic periodicities in lamination thicknesses reflect neapspring cycles and other earth-moon orbital parameters; these periodicities can be used to identify tidal deposits in Carboniferous rocks. Commonly preserved in tidal sedimentary rocks are neap/spring cycles and the semi-diurnal tidal inequality. Such deposits are widespread in the midcontinental USA

Neap-spring tidal cyclicity in laminated carbonate channel-fill deposits and its implications; Salem Limestone (Mississippian), south-central Indiana, U.S.A.

ABSTRACT Limestone beds containing rhythmic parallel laminations occur within a channel-fill sequence exposed locally in the Salem Limestone (Mississippian) of Indiana. The laminations consist of carbonate grains and micrite in layers up to 2 mm thick capped by thin (0.1-0.3 mm) drapes of organic matter. Each couplet was generated by mixed or semidiurnal tidal events, during which carbonate sediment was mobilized and deposited by the dominant tide and organic material settled from suspension during slackwater conditions. Laminae thicken and thin systematically in a vertical sequence as a result of neap-spring tidal current fluctuations that occur during a lunar month. Laminations are well preserved in certain beds ranging from 20 to 40 cm thick through much of the channel-fill sequence. Other beds are extensively bioturbated and contain only a partial record of the laminations. The sequence of bioturbated and unbioturbated units defines a rhythmic pattern, suggesting periods of seasonal environmental restriction that precluded burrowing organisms. Estimation of sedimentation rates based on the neap-spring tidal cycles indicates that deposition within the channel occurred very rapidly (averaging 35 cm/year), a rate four orders of magnitude faster than calculated long-term depositional rates.