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George E. Williams - One of the best experts on this subject based on the ideXlab platform.
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Comment on “Tidal Rhythmites and their implications” by R. Mazumder and M. Arima [Earth-Science Reviews, 69 (2005) 79–95]
Earth-Science Reviews, 2005Co-Authors: George E. WilliamsAbstract:Abstract The study of tidal Rhythmites, involving sedimentology, time-series analysis and astronomy, can contribute to understanding the history of the Earth's rotation and the Moon's orbit. It is regrettable, therefore, that the paper by Mazumder and Arima (2005) [Mazumder R., Arima M., 2005. Tidal Rhythmites and their implications. Earth-Sci. Rev. 69, 79–95.] on tidal Rhythmites and their implications contains errors of methodology and unsubstantiated speculation that could confuse and mislead. Moreover, contrary to the introductory statement of Mazumder and Arima (2005, p. 79) [Mazumder, R., Arima M., 2005. Tidal Rhythmites and their implications. Earth-Sci. Rev. 69, 79–95.] that the analysis of ancient tidal Rhythmites “is not straightforward”, the analysis need not be complicated. Problems will arise, however, if the Rhythmite raw data are of poor quality and basic astronomical laws are misapplied. Such shortcomings are to be found in the paper under discussion.
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geological constraints on the precambrian history of earth s rotation and the moon s orbit
Reviews of Geophysics, 2000Co-Authors: George E. WilliamsAbstract:Over the past decade the analysis of sedimentary cyclic Rhythmites of tidal origin, i.e., stacked thin beds or laminae usually of sandstone, siltstone, and mudstone that display periodic variations in thickness reflecting a strong tidal influence on sedimentation, has provided information on Earth's paleorotation and the evolving lunar orbit for Precambrian time (before 540 Ma). Depositional environments of tidal Rhythmites range from estuarine to tidal delta, with a wave-protected, distal ebb tidal delta setting being particularly favorable for the deposition and preservation of long, detailed Rhythmite records. The potential sediment load of nearshore tidal currents and the effectiveness of the tide as an agent of sediment entrainment and deposition are related directly to tidal range (or maximum tidal height) and consequent current speed. Hence the thickness of successive laminae deposited by tidal currents can be a proxy tidal record, with paleotidal and paleorotational values being determined by analysis of measured records of lamina and cycle thickness. The validity of the findings can be investigated by testing the primary, observed values for internal self-consistency through application of the laws of celestial mechanics. Paleotidal and paleorotational values provided by late Neoproterozoic (∼620 Ma) tidal Rhythmites in South Australia are validated by these tests and indicate 13.1±0.1 synodic (lunar) months/yr, 400±7 solar days/yr, a length of day of 21.9±0.4 h, and a relative Earth-Moon distance a/a0 of 0.965±0.005. The mean rate of lunar recession since that time is 2.17±0.31 cm/yr, which is little more than half the present rate of lunar recession of 3.82±0.07 cm/yr obtained by lunar laser ranging. The late Neoproterozoic data militate against significant overall change in Earth's moment of inertia and radius at least since 620 Ma. Cyclicity displayed by Paleoproterozoic (2450 Ma) banded iron formation in Western Australia may record tidal influences on the discharge and/or dispersal of submarine hydrothermal plumes and suggests 14.5±0.5 synodic months/yr and a/a0 = 0.906±0.029. The combined Rhythmite data give a mean rate of lunar recession of 1.24±0.71 cm/yr during most of the Proterozoic (2450–620 Ma), suggesting that a close approach of the Moon did not occur during earlier time. Concentrated study of Precambrian tidal Rhythmites promises to illuminate the evolving dynamics of the early Earth-Moon system and may permit the lunar orbit to be traced back to near the time of the Moon's origin.
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Geological constraints on the Precambrian history of the Earth’s rotation and the Moon’s orbit
2000Co-Authors: George E. WilliamsAbstract:Abstract. Over the past decade the analysis of sedi-mentary cyclic Rhythmites of tidal origin, i.e., stacked thin beds or laminae usually of sandstone, siltstone, and mudstone that display periodic variations in thickness reflecting a strong tidal influence on sedimentation, has provided information on Earth’s paleorotation and the evolving lunar orbit for Precambrian time (before 540 Ma). Depositional environments of tidal Rhythmites range from estuarine to tidal delta, with a wave-pro-tected, distal ebb tidal delta setting being particularly favorable for the deposition and preservation of long, detailed Rhythmite records. The potential sediment load of nearshore tidal currents and the effectiveness of the tide as an agent of sediment entrainment and deposition are related directly to tidal range (or maximum tida
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Precambrian tidal and glacial clastic deposits: implications for Precambrian Earth–Moon dynamics and palaeoclimate
Sedimentary Geology, 1998Co-Authors: George E. WilliamsAbstract:Abstract Over the past decade the study of Precambrian clastic tidal Rhythmites — stacked laminae of sandstone, siltstone and mudstone that display periodic variations in thickness reflecting a strong tidal influence on sedimentation — has provided accurate palaeotidal and palaeorotational data. Palaeotidal records obtained from tidal Rhythmites may be systematically abbreviated, however, and derived periods and frequencies can be misleading. The validity of such values, including past length of day, can be assessed by testing for internal self-consistency through application of the laws of celestial mechanics. Such a test supports the estimated length of day of 21.9±0.4 h derived from the late Neoproterozoic (∼620 Ma) Elatina–Reynella Rhythmites in South Australia, and the indicated mean rate of lunar retreat of 2.16±0.31 cm/year since ∼620 Ma. The validity of estimated lengths of day obtained from other Precambrian tidal Rhythmites remain unverified because the data sets contain only one primary value directly determined from the Rhythmites. The Elatina–Reynella data militate against significant Earth expansion at least since ∼620 Ma, and suggest that the free nutation or `tipping' of the Earth's fluid core has undergone a resonance with the Earth's annual forced nutation since the Neoproterozoic. Glaciogenic deposits are readily distinguishable from ejecta resulting from impacts with Earth-crossing bodies. Palaeomagnetic data, based on the geocentric axial dipole model for the geomagnetic field, indicate that Neoproterozoic and Palaeoproterozoic glaciation and cold climate near sea level occurred in low palaeolatitudes. This enigmatic finding may imply global glaciation or an increased obliquity of the ecliptic, and is relevant to modelling the effect of ice sheet formation on the Earth's obliquity history by obliquity–oblateness feedback mechanisms. Through multidisciplinary studies, clastic sedimentology and geophysics together can make substantial contributions to understanding Precambrian Earth–Moon dynamics and global palaeoenvironments.
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Precambrian length of day and the validity of tidal Rhythmite paleotidal values
Geophysical Research Letters, 1997Co-Authors: George E. WilliamsAbstract:Paleotidal records obtained from sedimentary tidal Rhythmites may be systematically abbreviated and so may give incorrect paleotidal and paleorotational values. The validity of determined values, including past length of day (l.o.d.), can be assessed by testing for internal self-consistency through application of the laws of celestial mechanics. Three independent values obtained from the ∼620-Ma Elatina-Reynella Rhythmites in South Australia (14.1 sidereal months/year, 401 sidereal days/year, and 19.5 years for the lunar nodal period), when employed in different equations that make allowance for lunar and solar tidal effects, each give a lunar semimajor axis in the range of 96.5–96.9% of the present figure. Such self-consistency strongly supports the validity of the derived l.o.d. of 21.9 hours at ∼620 Ma. The validity of the estimated l.o.d. of 20.9 hours at ∼900 Ma (revised value, Big Cottonwood Rhythmites, Utah) and of 17.1–18.9 hours at ∼2.5 Ga (Weeli Wolli Rhythmites, Western Australia) cannot be assessed in that way because each data set has only one directly determined value. The derived mean rate of lunar retreat of 2.16 cm/year since ∼620 Ma averts a close approach of the Moon at least since 3 Ga and a lower rate of retreat seems likely during the Proterozoic.
Anna C Snider - One of the best experts on this subject based on the ideXlab platform.
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deep water stratigraphic cyclicity and carbonate mud mound development in the middle cambrian marjum formation house range utah usa
Sedimentology, 2002Co-Authors: Maya Elrick, Anna C SniderAbstract:In mid-Middle Cambrian time, shallow-water sedimentation along the Cordilleran passive margin was abruptly interrupted by the development of the deep-water House Range embayment across Nevada and Utah. The Marjum Formation (330 m) in the central House Range represents deposition in the deepest part of the embayment and is composed of five deep-water facies: limestone–argillaceous limestone Rhythmites; shale; thin carbonate mud mounds; bioturbated limestone; and cross-bedded limestone. These facies are cyclically arranged into 1·5 to 30 m thick parasequences that include Rhythmite–mound, Rhythmite–shale, Rhythmite–bioturbated limestone and Rhythmite–cross-bedded limestone parasequences. Using biostratigraphically constrained sediment accumulation rates, the parasequences range in duration from ≈14 to 270 kyr. The mud mounds are thin (<2 m), closely spaced, laterally linked, symmetrical domes composed of massive, fenestral, peloidal to clotted microspar with sparse unoriented, poorly sorted skeletal material, calcitized bacterial(?) filaments/tubes and abundant fenestrae and stroma- tactoid structures. These petrographic and sedimentological features suggest that the microspar, peloids/clots and syndepositional micritic cement were precipitated in situ from the activity of benthic microbial communities. Concentrated growth of the microbial communities occurred during periods of decreased input of fine detrital carbonate transported offshore from the adjacent shallow-water carbonate platform. In the neighbouring Wah Wah Range and throughout the southern Great Basin, coeval mid-Middle Cambrian shallow-water carbonates are composed of abundant metre-scale, upward-shallowing parasequences that record high-frequency (104−105 years) eustatic sea-level changes. Given this regional stratigraphic relationship, the Marjum Formation parasequences probably formed in response to high-frequency sea-level fluctuations that controlled the amount of detrital carbonate input into the deeper water embayment. During high-frequency sea-level rise and early highstand, detrital carbonate input into the embayment decreased as a result of carbonate factory retrogradation, resulting in the deposition of shale (base of Rhythmite–shale parasequences) or thin nodular Rhythmites, followed by in situ precipitated mud mounds (lower portion of Rhythmite–mound parasequences). During the ensuing high-frequency sea-level fall/lowstand, detrital carbonate influx into the embayment increased on account of carbonate factory pro- gradation towards the embayment, resulting in deposition of Rhythmites (upper part of Rhythmite–mound parasequences), reworking of Rhythmites by a lowered storm wave base (cross-bedded limestone deposition) or bioturbation of Rhythmites by a weakened/lowered O2-minimum zone (bioturbated lime- stone deposition). This interpreted sea-level control on offshore carbonate sedimentation patterns is unique to Palaeozoic and earliest Mesozoic deep-water sediments. After the evolution of calcareous plankton in the Jurassic, the presence or absence of deeper water carbonates was influenced by a variety of chemical and physical oceanographic factors, rather than just physical transport of carbonate muds.
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Deep‐water stratigraphic cyclicity and carbonate mud mound development in the Middle Cambrian Marjum Formation, House Range, Utah, USA
Sedimentology, 2002Co-Authors: Maya Elrick, Anna C SniderAbstract:In mid-Middle Cambrian time, shallow-water sedimentation along the Cordilleran passive margin was abruptly interrupted by the development of the deep-water House Range embayment across Nevada and Utah. The Marjum Formation (330 m) in the central House Range represents deposition in the deepest part of the embayment and is composed of five deep-water facies: limestone–argillaceous limestone Rhythmites; shale; thin carbonate mud mounds; bioturbated limestone; and cross-bedded limestone. These facies are cyclically arranged into 1·5 to 30 m thick parasequences that include Rhythmite–mound, Rhythmite–shale, Rhythmite–bioturbated limestone and Rhythmite–cross-bedded limestone parasequences. Using biostratigraphically constrained sediment accumulation rates, the parasequences range in duration from ≈14 to 270 kyr. The mud mounds are thin (
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Deep-water stratigraphic cyclicity and carbonate mud mound development
2002Co-Authors: Maya Elrick, Anna C SniderAbstract:In mid-Middle Cambrian time, shallow-water sedimentation along the Cordilleran passive margin was abruptly interrupted by the development of the deep-water House Range embayment across Nevada and Utah. The Marjum Formation (330 m) in the central House Range represents deposition in the deepest part of the embayment and is composed of five deep-water facies: limestone–argillaceous limestone Rhythmites; shale; thin carbonate mud mounds; bioturbated limestone; and cross-bedded limestone. These facies are cyclically arranged into 1Æ5 to 30 m thick parasequences that include Rhythmite–mound, Rhythmite–shale, Rhythmite–bioturbated limestone and Rhythmite–cross-bedded limestone parasequences. Using biostratigraphically constrained sediment accumulation rates, the parasequences range in duration from 14 to 270 kyr. The mud mounds are thin (<2 m), closely spaced, laterally linked, symmetrical domes composed of massive, fenestral, peloidal to clotted microspar with sparse unoriented, poorly sorted skeletal material
Rajat Mazumder - One of the best experts on this subject based on the ideXlab platform.
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Tidal Rhythmites in a deep sea environment: An example from Mio-Pliocene Misaki Formation, Miura Peninsula, Japan
Marine and Petroleum Geology, 2013Co-Authors: Rajat Mazumder, Makoto ArimaAbstract:Abstract The Mio-Pliocene Misaki Formation, Miura Peninsula, Japan is characterized by alternation of mafic scoriaceous pebbly sandstone, pumiceous sandstone and siltstone, and mudstone formed in a fore-arc basin in an arc–arc collisional zone. The qualitative as well as quantitative evidences of tide during the Misaki sedimentation in the Jogashima area, Miura Peninsula are presented here. The lunar synodic period of ∼28 days/lunar month extracted from the Misaki tidal Rhythmite agrees well with the published Miocene tidal Rhythmite data. The couplet series of the Misaki tidal Rhythmite, however, is often interrupted by downslope resedimentation via turbidity currents, intense penecontemporaneous deformation and bioturbation. Association of deep sea turbidites, mass flow deposits and tidal Rhythmite suggest Misaki sedimentation in the Miura Peninsula took place in a submarine canyon setting.
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Tidal Rhythmites in offshore shale: A case study from the Palaeoproterozoic Chaibasa shale, eastern India and implications
Marine and Petroleum Geology, 2012Co-Authors: Leena Mallik, Rajat Mazumder, Makoto Arima, B.s. Mazumder, Priyanka ChatterjeeAbstract:Abstract Tidal Rhythmites have been documented from modern continental shelves and distal offshore settings. In significant contrast to their modern counterparts, sedimentological studies of ancient tidal Rhythmites formed in distal offshore settings and quantification of tidal rhythms encoded therein are, however, scarce. This paper presents sedimentological analysis of vertically accreted tidal Rhythmites from the Palaeoproterozoic Chaibasa shale facies in India, and quantification of their tidal rhythms. The facies characteristics of the Chaibasa Shale coupled with harmonic analysis of the laminae thicknesses of the sandstone inter-layers corroborate a distal shelf palaeogeography for the generation of the vertically accreted tidal Rhythmites. The latter are the distal counterparts of laterally accreted, tidal “bundle” deposits, well preserved within the shallow marine Chaibasa sandstones. The number of lunar days in a synodic month (∼23) estimated from the Chaibasa shale facies is, however, considerably lower than that estimated from the Chaibasa sandstone facies (∼32) suggesting that the tidal record encoded from the Chaibasa shale facies is incomplete.
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Reply to the comment of G. Williams on “Tidal Rhythmites and their implications” by R. Mazumder and M. Arima [Earth-Science Reviews 69 (2005), 79–95]
Earth-Science Reviews, 2005Co-Authors: Rajat MazumderAbstract:Dr. George Williams (Williams, 2005) provided me an opportunity to clarify the misunderstandings and misconceptions prevailing among some so-called tidal Rhythmite researchers. Ancient tidal Rhythmites, like their modern counterparts, can preserve a record of astronomically induced tidal periods. Unlike modern tide and tidal deposits, analysis of ancient tidal Rhythmites, however, is not straightforward. This is simply because spectral analysis of ancient tidal cycles is not an actual time series, but is in fact a thickness series. Many geologists use standard timeseries techniques while analyzing ancient tidal Rhythmites without concern to this basic fact! Complications are thus inherent with the analysis of ancient tidal Rhythmite. In discrete-signal records the relationship between sediment thickness and time is more complex than for continuous signal records (Weedon, 2003, p. 28–32) Understandably, quality of Rhythmite raw data and application of basic astronomical laws, if applicable at all, has nothing to do with these inherent complications. One of the major objectives
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implications of lunar orbital periodicity from the chaibasa tidal Rhythmite india of late paleoproterozoic age
Geology, 2004Co-Authors: Rajat MazumderAbstract:Harmonic analysis of the sandstone foreset-laminae thickness series from the Chaibasa tidal Rhythmite, India, clearly shows that a normal semidiurnal tidal system with synodic month of ;32 lunar days was in effect during the late Paleoproterozoic (2100‐1600 Ma). The minimum number of solar days in a lunar sidereal month was ;31. Published quantitative tidal-Rhythmite data of others in combination with data derived from the Chaibasa tidal Rhythmite indicate long-term stability of the lunar orbit and progressive increase in the Earth-Moon distance during the Proterozoic.
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Tidal Rhythmites and their implications
Earth-Science Reviews, 2004Co-Authors: Rajat Mazumder, Makoto ArimaAbstract:Abstract Tidal Rhythmites are unequivocal evidence of marine conditions in sedimentary basins and can preserve a record of astronomically induced tidal periods. Unlike modern tide and tidal deposits, analysis of ancient tidal Rhythmites, however, is not straightforward. This paper highlights the advances made in the tidal Rhythmite research in the last decade and reviews the methodologies of extracting lunar orbital periods from ancient tidal Rhythmites, the mathematics behind the use of tidalites, and their limitations and uncertainties. We have shown that analysis of ancient tidal Rhythmite may help us to estimate the palaeolunar orbital periods in terms of lunar days/month accurately. Determination of absolute Earth–Moon distances and Earth's palaeorotational parameters in the distant geological past from tidal Rhythmite, however, is ambiguous because of the difficulties in determining the absolute length of the ancient lunar sidereal month.
Maya Elrick - One of the best experts on this subject based on the ideXlab platform.
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Millennial-scale paleoclimate cycles recorded in widespread Palaeozoic deeper water Rhythmites of North America
Palaeogeography Palaeoclimatology Palaeoecology, 2006Co-Authors: Maya Elrick, Linda A. HinnovAbstract:Rhythmically interbedded limestone and shale or limestone and chert (“Rhythmites”) are a common feature of many deep-water Phanerozoic carbonate marine deposits. Seventeen different Palaeozoic Rhythmite successions from across North America (8 studied in detail, 9 studied in reconnaissance) are described and summarized. Individual Rhythmite couplets (4–20 cm thick) are composed of fine-grained, laminated to massive detrital limestone alternating with shale (or marl), or laminated spiculitic chert. Stratigraphic and primary depositional features within Rhythmites and associated facies indicates that the carbonate-rich and carbonate-poor interbedding is the result of repetitive changes in sediment input (primary) rather than due to diagenetic redistribution of calcareous material (secondary). The average duration of individual Rhythmite couplets is calculated using spectral analysis (to determine couplet thickness) combined with biostratigraphically calibrated undecompacted average sediment accumulation rates. The duration of Rhythmite couplets from the eight well studied successions ranges between ∼150 and ∼4900 yrs with the majority lying between ∼1000 and 3000 yrs; i.e., millennial scale. The paucity and low diversity of skeletal and trace fossils, preserved suspension laminae, lack of sediment reworking, and facies associations indicate Rhythmite accumulation was favored by: (1) deposition below storm-wave base which limited reworking by currents, (2) dysaerobic bottom waters which restricted bioturbation and intermixing of interbedded lithologies, and (3) proximity to nearshore carbonates supplying abundant fine-grained detrital carbonate. These combined conditions were best met along flooded, subtropical continental shelves or epeiric seas during My-scale (3rd-order) sealevel rises. The rhythmic alternation between carbonate-rich and carbonate-poor layers is interpreted to represent millennial-scale paleoclimatic changes related to: (1) wet/dry climate cycles which influenced the amount of continent-derived eolian and/or fluvial sediment input, (2) variations in offshore transport (via storm-generated or density currents) of nearshore-derived terrigenous or carbonate sediments, and/or (3) changes in wind-driven upwelling and availability of recycled biogenic silica. The various Rhythmite successions accumulated under dramatically different paleoenvironment and paleogeographic conditions including active to passive tectonic settings, equatorial to subtropical latitudes, long-term icehouse through greenhouse climatic conditions, calcite versus aragonitic seas, variable atmospheric CO2 concentrations, before and after land plant and animal evolution, and across widely varying ocean basin configurations. If our short-term paleoclimatic interpretations for the Rhythmites are correct, then it is apparent that millennial-scale climate changes occurred over a very wide spectrum of paleoceanographic, paleogeographic, paleoclimatic, tectonic, and biologic conditions and over time periods from the Cambrian to the Quaternary. Given this, it is difficult to invoke models of internally driven thermohaline oceanic oscillations or continental ice sheet instabilities to explain their origin. Instead, we suggest that
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deep water stratigraphic cyclicity and carbonate mud mound development in the middle cambrian marjum formation house range utah usa
Sedimentology, 2002Co-Authors: Maya Elrick, Anna C SniderAbstract:In mid-Middle Cambrian time, shallow-water sedimentation along the Cordilleran passive margin was abruptly interrupted by the development of the deep-water House Range embayment across Nevada and Utah. The Marjum Formation (330 m) in the central House Range represents deposition in the deepest part of the embayment and is composed of five deep-water facies: limestone–argillaceous limestone Rhythmites; shale; thin carbonate mud mounds; bioturbated limestone; and cross-bedded limestone. These facies are cyclically arranged into 1·5 to 30 m thick parasequences that include Rhythmite–mound, Rhythmite–shale, Rhythmite–bioturbated limestone and Rhythmite–cross-bedded limestone parasequences. Using biostratigraphically constrained sediment accumulation rates, the parasequences range in duration from ≈14 to 270 kyr. The mud mounds are thin (<2 m), closely spaced, laterally linked, symmetrical domes composed of massive, fenestral, peloidal to clotted microspar with sparse unoriented, poorly sorted skeletal material, calcitized bacterial(?) filaments/tubes and abundant fenestrae and stroma- tactoid structures. These petrographic and sedimentological features suggest that the microspar, peloids/clots and syndepositional micritic cement were precipitated in situ from the activity of benthic microbial communities. Concentrated growth of the microbial communities occurred during periods of decreased input of fine detrital carbonate transported offshore from the adjacent shallow-water carbonate platform. In the neighbouring Wah Wah Range and throughout the southern Great Basin, coeval mid-Middle Cambrian shallow-water carbonates are composed of abundant metre-scale, upward-shallowing parasequences that record high-frequency (104−105 years) eustatic sea-level changes. Given this regional stratigraphic relationship, the Marjum Formation parasequences probably formed in response to high-frequency sea-level fluctuations that controlled the amount of detrital carbonate input into the deeper water embayment. During high-frequency sea-level rise and early highstand, detrital carbonate input into the embayment decreased as a result of carbonate factory retrogradation, resulting in the deposition of shale (base of Rhythmite–shale parasequences) or thin nodular Rhythmites, followed by in situ precipitated mud mounds (lower portion of Rhythmite–mound parasequences). During the ensuing high-frequency sea-level fall/lowstand, detrital carbonate influx into the embayment increased on account of carbonate factory pro- gradation towards the embayment, resulting in deposition of Rhythmites (upper part of Rhythmite–mound parasequences), reworking of Rhythmites by a lowered storm wave base (cross-bedded limestone deposition) or bioturbation of Rhythmites by a weakened/lowered O2-minimum zone (bioturbated lime- stone deposition). This interpreted sea-level control on offshore carbonate sedimentation patterns is unique to Palaeozoic and earliest Mesozoic deep-water sediments. After the evolution of calcareous plankton in the Jurassic, the presence or absence of deeper water carbonates was influenced by a variety of chemical and physical oceanographic factors, rather than just physical transport of carbonate muds.
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Deep‐water stratigraphic cyclicity and carbonate mud mound development in the Middle Cambrian Marjum Formation, House Range, Utah, USA
Sedimentology, 2002Co-Authors: Maya Elrick, Anna C SniderAbstract:In mid-Middle Cambrian time, shallow-water sedimentation along the Cordilleran passive margin was abruptly interrupted by the development of the deep-water House Range embayment across Nevada and Utah. The Marjum Formation (330 m) in the central House Range represents deposition in the deepest part of the embayment and is composed of five deep-water facies: limestone–argillaceous limestone Rhythmites; shale; thin carbonate mud mounds; bioturbated limestone; and cross-bedded limestone. These facies are cyclically arranged into 1·5 to 30 m thick parasequences that include Rhythmite–mound, Rhythmite–shale, Rhythmite–bioturbated limestone and Rhythmite–cross-bedded limestone parasequences. Using biostratigraphically constrained sediment accumulation rates, the parasequences range in duration from ≈14 to 270 kyr. The mud mounds are thin (
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Deep-water stratigraphic cyclicity and carbonate mud mound development
2002Co-Authors: Maya Elrick, Anna C SniderAbstract:In mid-Middle Cambrian time, shallow-water sedimentation along the Cordilleran passive margin was abruptly interrupted by the development of the deep-water House Range embayment across Nevada and Utah. The Marjum Formation (330 m) in the central House Range represents deposition in the deepest part of the embayment and is composed of five deep-water facies: limestone–argillaceous limestone Rhythmites; shale; thin carbonate mud mounds; bioturbated limestone; and cross-bedded limestone. These facies are cyclically arranged into 1Æ5 to 30 m thick parasequences that include Rhythmite–mound, Rhythmite–shale, Rhythmite–bioturbated limestone and Rhythmite–cross-bedded limestone parasequences. Using biostratigraphically constrained sediment accumulation rates, the parasequences range in duration from 14 to 270 kyr. The mud mounds are thin (<2 m), closely spaced, laterally linked, symmetrical domes composed of massive, fenestral, peloidal to clotted microspar with sparse unoriented, poorly sorted skeletal material
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Millennial-scale climate origins for stratification in Cambrian and Devonian deep-water Rhythmites, western USA
Palaeogeography Palaeoclimatology Palaeoecology, 1996Co-Authors: Maya Elrick, Linda A. HinnovAbstract:Abstract Basinal facies of the Middle Cambrian Marjum Formation (western Utah) and Middle Devonian Denay Limestone (central Nevada) are characterized by thin, rhythmically interbedded limestone and marl layers (deep-water Rhythmites). Limestone layers (average thickness range of 4.3–5.5 cm) are composed of laminated to massive pelleted lime mudstone; marl layers (average thickness range of 0.7–1.7 cm) are characterized by laminated, argillaceous, dolomitic mudstone. The absence of current- or wave-reworked features, paucity of bioturbation and skeletal fossils, stratigraphic relationships with adjacent facies, and the dark color indicate that limestone and marl layers in both Rhythmite successions were deposited in quiet, dysaerobic waters below storm-wave base. Both limestone and marl layers are composed of submillimeter-thick graded laminae which represent discrete depositional events from dilute density currents generated by high-frequency storms or distal turbidity currents. Fluctuations in primary pelagic productivity cannot account for variations in carbonate influx because calcareous microfossils did not evolve until the Mesozoic. Instead, the rhythmic interbedding is interpreted to reflect climatically controlled variations in fluvial and/or eolian influx, or changes in marine currents (storm or distal turbidity currents) which transported shallow platform-derived carbonate material into the deep-water region. Spectral analysis of carbonate time series were compared to lithologic rank series and, particularly for the Middle Cambrian Rhythmites, were found to be statistically indistinguishable. The durations of significant spectral peaks were estimated from calculating the average sedimentation rates from the two biostratigraphically controlled stratigraphic sections; these rates range between 4.3 ± 4.1 cm/k.y. and 21.2 ± 29.2 cm/k.y. for the Cambrian, and 3.6 ± 1.8 cm/k.y. to 5.1 ± 7.4 cm/k.y. for the Middle Devonian. Application of these sedimentation rates to the Marjum couplets suggests that individual couplets represent between ∼190–2100 years of time. The Denay couplets represent ∼800–1900 years. The good agreement between empirical Holocene hemipelagic sedimentation rates and the sedimentologic evidence of relatively high depositional rates for the Paleozoic Rhythmites supports this millennial-scale interpretation. These results, combined with that from previous work in Paleozoic evaporite and carbonate successions, suggest that millennial-scale paleoclimatic variations affected marine and marginal-marine sedimentation as far back in time as the Cambrian. Millennial-scale climatic change appears to be a permanent feature affecting the oceans and atmosphere, and is apparently largely unaffected by major changes in Phanerozoic paleogeography, tectonics and atmospheric composition.
Kalle Lertola - One of the best experts on this subject based on the ideXlab platform.
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Miocene semidiurnal tidal Rhythmites in Madre de Dios, Peru
Geology, 2005Co-Authors: Jussi Hovikoski, Matti Räsänen, Murray Gingras, Martin Roddaz, Stéphane Brusset, Wilber Hermoza, Lidia Romero Pittman, Kalle LertolaAbstract:New data from upper Miocene deposits in the Madre de Dios region, southern Peru, allow the delineation of tidal regime for the first time in western Amazonia and provide strong evidence of elevated tidal range and brackish-water influence. The results point out the insufficiency of the current depositional models and support the earlier hypothesis that western Amazonia was also connected to the Paranan Sea during the late Miocene. In this paper we present sedimentological, ichnological, and statistical (Fourier transformation) data from two selected outcrops containing Rhythmite successions from an area that is traditionally considered as continental. The sediments are interpreted to represent tide-dominated, inner-middle estuarine deposits. The cyclic Rhythmites display semidiurnal cyclicity. The results are significant because (1) they contradict recent interpretations of the area's paleoenvironmental history; (2) the evidence for tidal processes is persuasive; and (3) the delineated tidal regime and range provide a unique insight into the depositional dynamics of a system having many important paleogeographic implications.