scholarly journals Field evidence suggests that the Palaeoproterozoic Gowganda Formation in Canada is non-glacial in origin

Geologos ◽  
2021 ◽  
Vol 27 (2) ◽  
pp. 73-91
Author(s):  
Mats O. Molén
Keyword(s):  
Recent Work ◽  
Debris Flows ◽  
Gravity Flow ◽  
Geological Evidence ◽  
Field Evidence ◽  
Gravity Flows ◽  
Geological Features

Abstract During more than a century since its original identification, the Gowganda Formation in Ontario (Canada) has gradually been reinterpreted from representing mainly subglacial tillites to secondary gravity flow and glaciomarine deposits. The main pieces of geological evidence advanced in favour of glaciation in recent articles are outsized clasts that have been interpreted as dropstones and patches of diamictites in a single small-sized area at Cobalt which is still interpreted as displaying subglacial basal tillites. The present research considers field evidence in the Gowganda Formation in the light of more recent work on gravity flows linked to tectonics. Detailed studies have demonstrated that the clasts which are interpreted to be dropstones rarely penetrate laminae and are commonly draped by sediments the appearance of which is similar to lonestones in gravity flows. The “subglacial area” at Cobalt displays evidence of tectonics and gravity flows, which can be traced from the underlying bedrock, and then further in the overlying sequence of diamictites and rhythmites. The sum of geological features displays appearances at odds with a primary glaciogenic origin, and there is no unequivocal evidence present of glaciation. The data indicate deposition by non-glaciogenic gravity flows, including cohesive debris flows for the more compact units, probably triggered by tectonic displacements.

scholarly journals Toe-of-slope facies of the Eocene limestones in Aghioi Pantes sequence (Zakynthos island, Western Greece)

2018 ◽  
Vol 34 (2) ◽  
pp. 699
Author(s):  
Μ. ΚΑΤΗ
Keyword(s):  
Shallow Water ◽  
Debris Flows ◽  
Depositional Environment ◽  
Facies Analysis ◽  
Facies Association ◽  
Gravity Flows ◽  
Carbonate Sequence ◽  
Western Greece ◽  
Water Carbonate ◽  
Water Facies

The facies analysis of the Eocene limestones in the Aghioi Pantes section in central Zakynthos, part of the Preapulian carbonate sequence in the greater area, showed three megafacies types: a) graded beds, in which two main subtypes have been recognized, medium- to thin-bedded calcarenites-calcilutites and thick-bedded ruditic calcarenites, consisting mainly of redeposited shallow-water carbonate sands (mostly bioclasts of nummulites and echinoids); based on their sedimentary structures they have been interpreted as low density turbidite and high density turbidite (or sandy debris flows) deposits correspondingly, b) calcareous conglomerates consisting of shallow-water facies lithoclasts and abundant pelagic intraclasts all of which have been interpreted as debris flow deposits and c) folded strata of pelagic-hemipelagic composition that have been interpreted as slumps. Subsequently, the studied limestones constitute exclusively deep-water resedimented facies having been deposited mainly through sediment gravity flows, carrying significant amounts of shallow-water bio- lithoclastic material. The distribution and the organization of this facies association, with the dominance in particular of the base cut-out turbidites, suggest as depositional environment of the studied Eocene limestones a "low" in the outer slope connecting the Preapulian platform with the adjacent Ionian basin.

scholarly journals The gravity flow dynamics of submarine fan sedimentation in the Magura Basin of the Western Carpathians (Magura Nappe, Slovakia)

2010 ◽  
Vol 61 (3) ◽  
pp. 201-209 ◽  
Author(s):  
František Teťák
Keyword(s):  
Deep Water ◽  
Flow Dynamics ◽  
Western Carpathians ◽  
Gravity Flow ◽  
Submarine Fan ◽  
Sedimentary Structures ◽  
Gravity Flows ◽  
Bed Thickness ◽  
Change Position ◽  
Current Arrangement

The gravity flow dynamics of submarine fan sedimentation in the Magura Basin of the Western Carpathians (Magura Nappe, Slovakia)This article deals with the dynamics of the deep-water gravity flows sedimentation within the Magura Formation. This investigation is based on analysis of the Magura sandstone sedimentary structures studied on the outcrops. The final comparison of the sedimentary structures and cycles with the paleocurrent directions provided an interpretation of the gravity flows dynamics and helped to restore the migration of the sandy lobes in space and time. Three modes of sedimentation are recorded: regular cyclic sedimentation from the lobe, irregular sedimentation from the immature lobe and pelitic sedimentation on the basin plane without the lobe influence. We compared the occurrence of some sedimentary structures with the changes of the current directions and bed thickness. The following interpretations of gravity flow fan dynamics are results of this comparision: the fan consists of one or several lobes, the lobe branches out into branches with the radial current arrangement, the lobes laterally change position and the lobes suddenly die out.

scholarly journals New Zealand Glaciations and the Duration of The Pleistocene

1961 ◽  
Vol 3 (29) ◽  
pp. 940-943 ◽  
Author(s):  
Maxwell Gage
Keyword(s):  
New Zealand ◽  
Recent Work ◽  
Late Pleistocene ◽  
Early Pleistocene ◽  
Pleistocene Glaciation ◽  
Shield Volcano ◽  
Geological Evidence ◽  
Pleistocene Period

Abstract Recent work has resulted in recognition of an additional glaciation preceding the Waimaunga Glaciation in the late Pleistocene. This followed the mid-Pleistocene climax of earth movements responsible for most of the present mountainous relief of New Zealand, but only after an interval of time long enough for the construction and subsequent deep dissection of Banks Peninsula shield volcano. It is inferred from this and other geological evidence that the earliest late Pleistocene glaciation was separated from the early Pleistocene Ross Glaciation by several hundred thousand years, and that the Pleistocene Period altogether covers at least one million years.

scholarly journals The origin of upper Precambrian diamictites, northern Norway: a case study applicable to diamictites in general

Geologos ◽  
2017 ◽  
Vol 23 (3) ◽  
pp. 163-181 ◽  
Author(s):  
Mats O. Molén
Keyword(s):  
Quartz Sand ◽  
Laboratory Data ◽  
Gravity Flow ◽  
Geological Data ◽  
Submarine Fan ◽  
Northern Norway ◽  
Gravity Flows ◽  
Material Evidence ◽  
Geological Context

AbstractUpper Precambrian diamictites in Varangerfjorden (northern Norway) have been examined for evidence of origin, whether glaciogenic, gravity flow or polygenetic. Studies of geomorphology, sedimentology and surface microtextures on quartz sand grains are integrated to provide multiple pieces of evidence for the geological agents responsible for the origin of the diamictites. The documented sedimentary and erosional structures, formerly interpreted in a glaciogenic context (e.g., diamict structure, pavements and striations) have been reanalysed. Field and laboratory data demonstrate that, contrary to conclusions reached in many earlier studies, the diamictites and adjacent deposits did not originate from glaciogenic processes. Evidence from macrostructures may occasionally be equivocal or can be interpreted as representing reworked, glacially derived material. Evidence from surface microtextures, from outcrops which are believed to exhibit the most unequivocal signs for glaciation, display no imprint at all of glaciogenic processes, and a multicyclical origin of the deposits can be demonstrated. The geological context implies (and no geological data contradict this) an origin by gravity flows, possibly in a submarine fan environment. This reinterpretation of the diamictites in northern Norway may imply that the palaeoclimatological hypothesis of a deep frozen earth during parts of the Neoproterozoic has to be revised.

scholarly journals Configuration and Dynamics of the Laurentide Ice Sheet During the Late Wisconsin Maximum

2007 ◽  
Vol 36 (1-2) ◽  
pp. 5-14 ◽  
Author(s):  
Arthur S. Dyke ◽  
Lynda A. Dredge ◽  
Jean-Serge Vincent
Keyword(s):  
Ice Sheet ◽  
Gravity Anomalies ◽  
Late Glacial ◽  
Laurentide Ice Sheet ◽  
Geological Evidence ◽  
Original Proposal ◽  
Field Evidence ◽  
Free Air ◽  
Free Air Gravity ◽  
Basin Region

ABSTRACT Prior to 1943 the Laurentide Ice Sheet was considered to have three major domes centered in Keewatin, Labrador, and Patricia (TYRRELL, 1898 a, b; 1913). FLINT (1943) argued that these centres were of only local and temporary importance and favoured a single-domed ice sheet. Despite the lack of supporting geological evidence, and despite the proposition of a Foxe Dome in the interim (IVES and ANDREWS, 1963), the single-dome concept was not seriously challenged until the late 1970's and, in fact, is still strenuously supported (HUGHES era/., 1977 ; DENTON and HUGHES, 1981). This paper extends and modifies recent conclusions that the Laurentide Ice Sheet had more than one dome at the Late Wisconsin maximum. We propose a model incorporating five domes (M'Clintock, Foxe, Labrador, Hudson, and (?) Caribou) based on the position of ice divides, ice flow patterns, drift composition, late-glacial features, postglacial isostatic recovery and free-air gravity anomalies. Our Labrador and Hudson domes closely correspond to Tyrrell's Labradorean and Patrician ice sheets; our Caribou and M'Clintock domes together with the Franklin Ice Complex over the Queen Elizabeth Islands north of the Laurentide Ice Sheet, correspond to Tyrrell's original Keewatin Ice Sheet. The style of glaciation of the Foxe Basin region was not known to Tyrrell, but our reconstruction of the Foxe Dome is in close agreement with the original proposal of Ives and Andrews. Like Tyrrell, our reconstruction is based on field evidence obtained through extensive mapping; the single dome model continues to be unsupported by geological data.

scholarly journals Rapid gravity flow transformation revealed in a single climbing ripple

Geology ◽  
2020 ◽  
Author(s):  
Jaco H. Baas ◽  
Jim Best ◽  
Jeff Peakall
Keyword(s):  
Plug Flow ◽  
Gravity Flow ◽  
Small Scale ◽  
Geometrical Characteristics ◽  
Gravity Flows ◽  
Sediment Gravity Flow ◽  
Wide Range ◽  
Sediment Deformation ◽  
Rheological Character ◽  
Current Ripples

Sediment gravity flows demonstrate a wide range of rheological behaviors, and past work has shown how transformations between flow types generate spatiotemporal changes in the resultant sedimentary successions. We used the geometrical characteristics of a single climbing ripple to demonstrate how such flows can transform from a turbulent to a quasi-laminar plug flow, with the transitional clay flow sequence being manifested by abnormally large heterolithic sand-clay current ripples with small backflow ripples, and then abundant clay deposition associated with smaller ripples. Analysis of ripple size, angle of climb, grain size, internal erosional surfaces, and soft-sediment deformation suggests that transformation in the rheological character of the sediment gravity flow was rapid, occurring over a period of tens of minutes, and thus probably over a spatial scale of hundreds of meters to several kilometers. Our study indicates how the character of flow transformation can be elucidated from the details of a small-scale sedimentary structure.

A REVIEW OF BORON SEDIMENTARY GEOCHEMISTRY IN RELATION TO NEW ANALYSES OF SOME NORTH AMERICAN SHALES

1966 ◽  
Vol 3 (1) ◽  
pp. 49-63 ◽  
Author(s):  
D. M. Shaw ◽  
R. Bugry
Keyword(s):  
Recent Work ◽  
North American ◽  
Geological Evidence ◽  
B Values ◽  
Free Basis ◽  
Sedimentary Geochemistry ◽  
Mineral Phases ◽  
Secular Variations

One hundred and sixty-eight North American shales, ranging in age from Proterozoic to Cretaceous, have been analyzed for boron; analyses for CO2 permitted corrections to a carbonate-free basis. The B values mostly agree with the inferred salinities of the environments of deposition, based on geological evidence: anomalously low values in the Devonian Littleton formation may be correlated with loss of B to regional quartz–tourmaline veins.The data do not permit drawing any inference regarding secular variations in oceanic B content.A review of recent work on B sedimentary geochemistry indicates the need for analyses of real, rather than hypothetical, mineral phases.

Continental displacement and expansion of the earth during the Mesozoic and Cenozoic

1976 ◽  
Vol 281 (1303) ◽  
pp. 223-291 ◽  
Keyword(s):  
Upper Jurassic ◽  
Mean Value ◽  
Ocean Floor ◽  
The Arctic ◽  
Late Triassic ◽  
Geological Evidence ◽  
Global Expansion ◽  
Field Evidence ◽  
Constant Dimension ◽  
Ocean Floor Spreading

Most reconstructions of Pangaea, the early Mesozoic supercontinent, assume an Earth of modern dimensions. Such reconstructions produce major geometric and Earth of modern dimensions. Such reconstructions produce major geometric and geological fit inconsistencies particularly in areas such as the Arctic, Caribbean, Mediterranean, and southeast Asia and Indonesia. The ocean floor spreading history of these regions and the adjacent oceans indicates that they have grown by areal expansion since their initiation. In contrast, the various reconstructions of Mesozoic and Cenozoic stages which assume an Earth of constant dimensions, require that these regions, either initially or during their development, should contract in area. The geological evidence from the continental margins and from the Earth’s oceans does not support the amount of subduction, either in whole or in part, required by the constant dimension hypothesis. It is shown that an exact fit of the various continental fragments together to reform Pangaea, which agrees with the geometric and geological matches, is obtained when the value of the Earth’s surface curvature is increased to the point at which the diameter of the globe is 80 % of its current mean value. This corresponds in time to the late Triassic-early Jurassic. It is asserted that the early Upper Jurassic to Recent ocean floor spreading data now available, displayed here in maps, also demonstrate progressive global expansion commensurate with an increase in diameter of 20 % of the Earth’s current mean value. Series of maps employing a zenithal equidistant projection are used to illustrate stages in the inferred development of certain regions during the Mesozoic and Cenozoic according to the ocean floor spreading data. The global expansion deduced from the geometric requirements of the spreading data in these maps permits a much more straightforward reading of the development of ocean basins and associated displacement of continents; one which accords with the field evidence. The inconsistencies seen in constant dimensions reconstructions do not arise. The results are summarized in outline hemisphere maps for which a new cartographic projection has been developed.

scholarly journals Earthquake-induced debris flows at Popocatépetl Volcano, Mexico

2021 ◽  
Vol 9 (3) ◽  
pp. 393-412
Author(s):  
Velio Coviello ◽  
Lucia Capra ◽  
Gianluca Norini ◽  
Norma Dávila ◽  
Dolors Ferrés ◽  
...  
Keyword(s):  
Debris Flows ◽  
Active Volcano ◽  
Horizontal Stress ◽  
Structural Features ◽  
Joint Effect ◽  
Volcanic Edifice ◽  
Field Evidence ◽  
Intraslab Earthquake ◽  
Popocatépetl Volcano ◽  
Popocatepetl Volcano

Abstract. The 2017 Mw 7.1 Puebla–Morelos intraslab earthquake (depth: 57 km) severely hit Popocatépetl Volcano, located ∼ 70 km north of the epicenter. The seismic shaking triggered shallow landslides on the volcanic edifice, mobilizing slope material saturated by the 3 d antecedent rainfall. We produced a landslide map based on a semi-automatic classification of a 50 cm resolution optical image acquired 2 months after the earthquake. We identified hundreds of soil slips and three large debris flows for a total affected area of 3.8 km2. Landslide distribution appears controlled by the joint effect of slope material properties and topographic amplification. In most cases, the sliding surfaces correspond with discontinuities between pumice-fall and massive ash-fall deposits from late Holocene eruptions. The largest landslides occurred on the slopes of aligned ENE–WSW-trending ravines, on opposite sides of the volcano, roughly parallel to the regional maximum horizontal stress and to volcano-tectonic structural features. This suggests transient reactivation of local faults and extensional fractures as one of the mechanisms that weakened the volcanic edifice and promoted the largest slope failures. The material involved in the larger landslides transformed into three large debris flows due to liquefaction. These debris flows mobilized a total volume of about 106 m3 of material also including large wood, were highly viscous, and propagated up to 7.7 km from the initiation areas. We reconstructed this mass wasting cascade by means of field evidence, samples from both landslide scarps and deposits, and analysis of remotely sensed and rainfall data. Although subduction-related earthquakes are known to produce a smaller number of landslides than shallow crustal earthquakes, the processes described here show how an unusual intraslab earthquake can produce an exceptional impact on an active volcano. This scenario, not related to the magmatic activity of the volcano, should be considered in multi-hazard risk assessment at Popocatépetl and other active volcanoes located along volcanic arcs.

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