The influence of subaerial exposure on the bulk properties of fine-grained intertidal sediment from Minas Basin, Bay of Fundy

1988 ◽  
Vol 27 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Carl L. Amos ◽  
Nancy A. Van Wagoner ◽  
Graham R. Daborn
Keyword(s):  
Intertidal Sediment ◽  
Bay Of Fundy ◽  
Bulk Properties ◽  
Fine Grained ◽  
Subaerial Exposure

Erosion and deposition of fine-grained sediments from the Bay of Fundy

Sedimentology ◽  
1985 ◽  
Vol 32 (6) ◽  
pp. 815-832 ◽  
Author(s):  
CARL L. AMOS ◽  
DAVID C. MOSHER
Keyword(s):  
Bay Of Fundy ◽  
Erosion And Deposition ◽  
Fine Grained

scholarly journals The Aztec Siltstone: an Upper Devonian Alluvial Plain Red Bed Sequence, Southern Victoria Land, Antarctica

2021 ◽  
Author(s):  
◽  
John Gordon McPherson
Keyword(s):  
Water Table ◽  
Ferric Oxide ◽  
Alluvial Plain ◽  
Heavy Minerals ◽  
Fine Grained ◽  
Subaerial Exposure ◽  
Hydrated Ferric Oxide ◽  
Victoria Land ◽  
Clay Matrix ◽  
Red Bed

<p>The Aztec Siltstone (late Devonian) crops out for 150 km along the Transantarctic Mountains, between the Mawson and Mulock Glaciers of southern Victoria Land, Antarctica. It is the uppermost formation of the Taylor Group, the lower of the two subdivisions of the Beacon Supergroup of southern Victoria Land. The formation consists largely of fine to medium-grained sandstone, and greyish red (10R 4/2), grey (N5), and greenish grey (5G 6/1) siltstone and claystone. Other lithologies include carbonaceous siltstone and claystone, limestone and intraformational conglomerate. Conchostracans, fish fossils, plant fragments, and gypsum lenses are present also. Cross-stratification, horizontal stratification, channelling, and "fining-upwards" cycles indicate deposition from shallow, high sinuosity (tortuous), meandering streams that migrated laterally across a broad alluvial plain. The sandstone beds are laterally accreted channel deposits, whereas the siltstone and claystone beds represent overbank deposition by vertical accretion in the interchannel areas of the floodbasin. Other floodbasin deposits include lacustrinal sediments from pluvial ponds and ox-bow lakes, and palustrinal sediments from the backswamps. Overbank deposition of bed load material formed levees, and stream avulsion and crevassing during flood stage produced crevasse-splay deposits. The sandstone beds are quartzarenites, with detrital grains consisting largely of plutonic quartz; other grains include chert, feldspar, metamorphic quartz and a trace of heavy minerals. Sandstone textures average fine-grained and well sorted, although sandstone with textural inversion is common. Compositional and textural characteristics indicate that the sandstone is a product of the reworking of older quartzarenite in the source area. Subaerial exposure was a feature of the fine-grained floodbasin sediments; the evidence includes the abundance of mudcracks, and a variety of soil features. The latter include extensive kankar ('calichea') horizons, pseudo- or wavey bedding structures, a compositional and textural similarity to modern soils, vein networks (considered to be a product of deep cracking in the unconsolidated. substratum), burrowing, and root horizons with in some cases associated plant fragments. The kankar ('calichea') suggests that there was a period of prolonged subaerial exposure and soil development which followed the deposition of fine-grained, fine member lithologies of the "fining upwards" cycles. This period was probably in the range 5,000 to 50,000 years. The Aztec Siltstone is a typical "variegated" red-bed sequence, containing interbedded red and drab fine-grained lithologies. The fine-grained drab lithologies consist of quartz grains set in a matrix of green illitic and chloritic clay. The colour in the interbedded red and grey siltstone and claystone results from a haematite pigment, which in the red samples is present in a concentration sufficient to completely mask the green colour of the clay matrix. The reddening is believed to have been a penecontemporaneous process that took place in the floodbasin sediments during their prolonged subaerial exposure under a hot and seasonally wet and dry (savanna) climate. The haematitic pigment was derived from the in situ and progressive dehydration of detrital amorphous and poorly crystalline brown hydrated ferric oxide in those sediments which maintained an oxidizing environment and were above the ground-water table during the dehydration process. Sediments which remained in a water-logged state, below the water table, and in association with organic matter, were invariably reduced and lost their iron oxide in solution. Later post-depositional reduction of some red lithologies produced reduction spheres and channels, reduced burrows and vein networks, and the reduced layers immediately underlying the scoured surface at the base of the channel sandstones. Some chemical redistribution of iron contributed to the variegated and mottled horizons of the formation. The mineral composition of adjacent red and drab lithologies is essentially the same except for the haematite constituent. The red average 5.86 ([delta] = 1.09) percent total Fe (as Fe2O3), of, which 3.01 ([delta] = 0.63) percent is as haematite pigment, 1.57 percent Fe2O3 is in a combined form (probably as ferric silicates), and 1 14 ([delta] = 0.57) percent is as FeO. The green average 3.65 ([delta] = 1.81) percent total Fe (as Fe2O3) of which approximately 0.27 percent is as haematite pigment, approximately 1.4 percent Fe2O3 is in a combined form, and 1.77 ([delta] = 1.37) percent is as FeO. In the majority of the green lithologies the free ferric oxide (as haematite or hydrated ferric oxide) was removed in solution during reduction, and at the same time minor amounts of clay matrix were also leached out.</p>

Geochemical factors controlling the accumulation and dispersal of heavy metals in the Bay of Fundy sediments

1982 ◽  
Vol 19 (5) ◽  
pp. 930-944 ◽  
Author(s):  
D. H. Loring
Keyword(s):  
Source Rocks ◽  
Bay Of Fundy ◽  
Fine Grained ◽  
Anthropogenic Inputs ◽  
Geochemical Factors ◽  
Industrial Sources ◽  
High Concentrations ◽  
Abundance And Distribution ◽  
Local Anomalies ◽  
Nova Scotian

Total Zn, Cu, Pb, Co, Ni, Cr, V, Hg, Be, As, Ba, and Se concentrations vary regionally and in response to textural variations of the sediments of the Bay of Fundy. They are, except for local anomalies, at or near natural levels in relation to their source rocks and other unpolluted marine sediments.Chemical partition indicates that small but significant amounts (1–27%) of the total element concentrations are potentially available to the biota. Potential bioavailable metals are derived from natural and industrial sources and are held in the sediments by fine grained organic material (Hg, Pb), hydrous iron oxides (Cr, V, Co, Pb), ion exchange positions (Zn), and calcareous components (Cu, Zn, Ba).Of the total metal content, however, 73–99% is not readily available to the biota but held in various sulphide (Zn, Cu, Pb, As, Se), oxide (Cr, Ni, Co, V), and silicate minerals (Cr, V, Co, Ni). The host minerals have accumulated at the same rates as other detrital material except for particles of zinc oxide that have been derived from industrial sources adjacent to the Bay of Fundy. The accumulations of fine grained host minerals are the main control on the abundance and distribution of Hg, Be, Zn, Pb, and As in the sediments whereas the dispersal of the ferromagnesian silicates and various oxide minerals, rather than the grain size of their hosts, accounts for dispersal of Cr, V, Co, and Ni in the sediments. These factors together with the present depositional pattern of the particles account for the accumulation and relative enrichment of most metals along with other fine grained materials in the "Quoddy region" of the bay. Local anomalies of detrital minerals related to bedrock exposures also account for high concentrations of Cr, V, and Ni in the vicinity of Grand Manan Island and along the Nova Scotian coast. Relatively high metal concentrations also occur near a dredge dispersal site off St. John Harbour and may reflect the initial impact of anthropogenic inputs on the natural levels of metals in the Fundy sediments.

scholarly journals Paleoenvironments and sequential stratigraphy of Ordovician marginal marine deposits of Sierra de Zapla (Sierras Subandinas, northwestern Argentina) and their relation with the Central Andean Basin

2010 ◽  
Vol 33 (2) ◽  
pp. 247
Author(s):  
Ricardo A. Astini ◽  
Larisa F. Marengo
Keyword(s):  
Main Tool ◽  
High Energy ◽  
Gradual Change ◽  
Fine Grained ◽  
Marine Deposits ◽  
Ice Cap ◽  
Subaerial Exposure ◽  
Stage 4 ◽  
Glacial Stage ◽  
Paleocurrent Analysis

The best and most complete palynologically constrained Ordovician section across the Sierras Subandinas crops out in the southern part of the Sierra de Zapla along the Capillas River (Subandean Ranges, Jujuy Province). The dominantly marginal marine setting explains the scarcity of invertebrates throughout the section. Palynomorphs are the main tool in stratigraphic studies of the area and trace fossils are important aids in paleoenvironmental analysis. Based on a detailed facies analysis, geometry and paleocurrent analysis, and recognition of key surfaces, four depositional sequences (S1-S4) with different internal arrangements and compatible with 3rd order cycles were identified. The Zanjón Formation (upper part of Global Stage 2 and Global Stage 3) with unexposed base, initiates the stratigraphic section and it is characterized by a heterolithic facies association with subordinate storm layers, thin-bedded phosphate-rich micro-conglomerates and inarticulate-rich shell beds. Common subaerial exposure features like truncated ripple tops and mud cracks suggest tidal flat environments. This interval yields a mixed Skolithos-Cruziana ichnofacies. Towards the top, an increase in mottling and a gradual change into dominant purplish-red colors (Laja Morada Member of the Labrado Formation) indicate a protracted subaerial emergence during a Darriwilian (Global Stage 4) relative sea-level drop, and a fluctuating water table in interfluves. This unit is covered in sharp erosive boundary by the Lagunilla Member of the Labrado Formation, suggesting development of composite fluvial incisions. Sandy fluvial to tide-dominated estuarine fills and thoroughly-bioturbated subtidal hetherolithic beds overlie the sequence boundary representing a typical transgressive systems tract. Development of surfaces with dominant Skolithos forms are interpreted as representing Glossifungites ichnofacies typically indicating by-pass erosion and firm-ground development previous to reworking of interfluves by advancing ravinement surface. The Capillas Formation (upper Darriwilian and lower part of Global Stage 5), sharply levels the previous estuarine complexes and represents a fine-grained wedge that gradually coarsens up. This unit contains the only truly marine shelly fauna concentrated in few storm beds above the fine-grained interval that characterizes a maximum flooding stage. This is the only interval that can be positively correlated with sections in the Cordillera Oriental to the west and Bolivia. A gradual coarsening to silty sandstones and the replacement of Cruziana by Skolithos dominated ichnofacies suggest a shallowing-upward section, capped by the thick-bedded, high energy quartz sandstones with pipe-rock structures of the Centinela Formation (middle and upper part of Global Stage 5). A shallowing-upward trend indicates the progradation of deltaic complexes, which in turn were erosively truncated by the waxing stage of the Gondwanan Hirnantian (uppermost Ordovician) ice-cap represented by the Zapla Formation (Global Stage 6) along the Central Andes. Above the diamictite-rich Zapla Formation the Lipeón Formation (Silurian) is interpreted as related to repeated transgressive ravinement surfaces that truncated Fe+2 saturated estuaries after a waning glacial stage and isostatic rebound, favouring the deposition of oolitic ironstones and succeeded by the development of a Zoophycos dominated muddy shelf.

In situ erosion measurements on fine-grained sediments from the Bay of Fundy

1992 ◽  
Vol 108 (2) ◽  
pp. 175-196 ◽  
Author(s):  
Carl L Amos ◽  
G.R Daborn ◽  
H.A Christian ◽  
A Atkinson ◽  
A Robertson
Keyword(s):  
Bay Of Fundy ◽  
Fine Grained

Paleoalterações e Carbonatos em Depósitos Aluviais na Região de Santa Maria, Triássico Médio a Superior do Sul do Brasil

2004 ◽  
Vol 31 (1) ◽  
pp. 3 ◽  
Author(s):  
ÁTILA AUGUSTO STOCK DA ROSA ◽  
NUNO LAMAS VALENTE PIMENTEL ◽  
UBIRATAN FERRUCIO FACCINI
Keyword(s):  
Stratigraphic Correlation ◽  
Carbonate Precipitation ◽  
Southern Brazil ◽  
Fluvial Deposits ◽  
Fine Grained ◽  
Weathering Processes ◽  
Subaerial Exposure ◽  
Fossil Preservation ◽  
Santa Maria ◽  
Mn Oxides

Five types of paleo-weathering and carbonate precipitation were recognized in fine-grained deposits of the Alemoa Member, Santa Maria Formation, Middle to Upper Triassic of southern Brazil. The fauna and flora found in these lithologies are important dating tools, but only in a generic way, misleading the time involved in periods of deposition and non deposition. The identified types of deposits are (i) reddish mudstones, with none or little paleo-weathering, (ii) mottled mudstones, with incipient pedogenesis, mainly mottling, destratification, animal and vegetal colonization, (iii) carbonate veins, with more evidences of exposure and root action, (iv) carbonate siltstones/sandstones, where restricted fluvial deposits are cemented by phreatic carbonate, and (v) carbonate nodules and lenses, in which small lenses of a very compact calcrete are at the top and in the center of carbonated siltstone/sandstone beds, distinguished by its crystalinity, hardness and brighter color. The recorded microfacies point to a cyclic variation of the mainly high phreatic level, forming cracks and pedotubules (pedogenesis) filled with carbonate and Fe and Mn oxides (phreatic). The identification of five distinct pedofacies and the stratigraphic correlation in the sedimentary package of the Alemoa Member (base, middle or topmost position) suggest a probable association of paleo-weathering processes and vertebrate preservation. Near channel facies, mainly at the base and top, present smaller exposure periods and higher variations on the phreatic level, and consequently, the best preserved vertebrate fossils. On the other hand, facies which are far from the channel, record more subaerial exposure and more significant phreatic variation, leading to more advanced (although still incipient) paleo-weathering and carbonate precipitation, and to a worst fossil preservation.

Textural and Isotopic Variations in Diagenetic Kaolinite from the Magnus Oilfield Sandstones

Clay Minerals ◽  
1993 ◽  
Vol 28 (4) ◽  
pp. 625-639 ◽  
Author(s):  
C. I. Macaulay ◽  
A. E. Fallick ◽  
R. S. Haszeldine
Keyword(s):  
Isotopic Composition ◽  
Meteoric Water ◽  
Upper Jurassic ◽  
Coarse Grained ◽  
Pore Waters ◽  
Burial Diagenesis ◽  
Fine Grained ◽  
The North ◽  
Subaerial Exposure ◽  
The North Sea

AbstractIn Upper Jurassic sandstones of the Magnus Sandstone Member from the Magnus Oilfield in the North Sea, diagenetic kaolinite morphology and isotopic composition vary away from the Late Cimmerian unconformity. Near the unconformity, coarse-grained (15-30 μm) vermiform kaolinite morphology is most common, whereas downdip, 3 km away, fine-grained (∼10 μm) blocky morphology is prevalent. Kaolinite abundances increase downdip, away from the unconformity, and kaolinite near the unconformity has low δ18O (12·5-14·9%o smow) compared to that downdip (15·9−17·5%o). This reflects replacement of marine depositional pore-waters by meteoric water near the erosion surface. However, isotopic temperature estimates suggest that the majority of kaolinite formed at elevated burial temperatures of ~80°C, and not during subaerial exposure of the sandstone. The δD of kaolinite close to the unconformity is also lower than that downdip. Kaolinite morphology and isotopic composition record meteoric water ingress during Late Cimmerian subaerial erosion and retention of meteoric-derived water in the crest of the Magnus structure during burial diagenesis. Kaolinite formation during subaerial exposure is not of significance to the sandstone reservoir quality.

scholarly journals The Aztec Siltstone: an Upper Devonian Alluvial Plain Red Bed Sequence, Southern Victoria Land, Antarctica

2021 ◽  
Author(s):  
◽  
John Gordon McPherson
Keyword(s):  
Water Table ◽  
Ferric Oxide ◽  
Alluvial Plain ◽  
Heavy Minerals ◽  
Fine Grained ◽  
Subaerial Exposure ◽  
Hydrated Ferric Oxide ◽  
Victoria Land ◽  
Clay Matrix ◽  
Red Bed

<p>The Aztec Siltstone (late Devonian) crops out for 150 km along the Transantarctic Mountains, between the Mawson and Mulock Glaciers of southern Victoria Land, Antarctica. It is the uppermost formation of the Taylor Group, the lower of the two subdivisions of the Beacon Supergroup of southern Victoria Land. The formation consists largely of fine to medium-grained sandstone, and greyish red (10R 4/2), grey (N5), and greenish grey (5G 6/1) siltstone and claystone. Other lithologies include carbonaceous siltstone and claystone, limestone and intraformational conglomerate. Conchostracans, fish fossils, plant fragments, and gypsum lenses are present also. Cross-stratification, horizontal stratification, channelling, and "fining-upwards" cycles indicate deposition from shallow, high sinuosity (tortuous), meandering streams that migrated laterally across a broad alluvial plain. The sandstone beds are laterally accreted channel deposits, whereas the siltstone and claystone beds represent overbank deposition by vertical accretion in the interchannel areas of the floodbasin. Other floodbasin deposits include lacustrinal sediments from pluvial ponds and ox-bow lakes, and palustrinal sediments from the backswamps. Overbank deposition of bed load material formed levees, and stream avulsion and crevassing during flood stage produced crevasse-splay deposits. The sandstone beds are quartzarenites, with detrital grains consisting largely of plutonic quartz; other grains include chert, feldspar, metamorphic quartz and a trace of heavy minerals. Sandstone textures average fine-grained and well sorted, although sandstone with textural inversion is common. Compositional and textural characteristics indicate that the sandstone is a product of the reworking of older quartzarenite in the source area. Subaerial exposure was a feature of the fine-grained floodbasin sediments; the evidence includes the abundance of mudcracks, and a variety of soil features. The latter include extensive kankar ('calichea') horizons, pseudo- or wavey bedding structures, a compositional and textural similarity to modern soils, vein networks (considered to be a product of deep cracking in the unconsolidated. substratum), burrowing, and root horizons with in some cases associated plant fragments. The kankar ('calichea') suggests that there was a period of prolonged subaerial exposure and soil development which followed the deposition of fine-grained, fine member lithologies of the "fining upwards" cycles. This period was probably in the range 5,000 to 50,000 years. The Aztec Siltstone is a typical "variegated" red-bed sequence, containing interbedded red and drab fine-grained lithologies. The fine-grained drab lithologies consist of quartz grains set in a matrix of green illitic and chloritic clay. The colour in the interbedded red and grey siltstone and claystone results from a haematite pigment, which in the red samples is present in a concentration sufficient to completely mask the green colour of the clay matrix. The reddening is believed to have been a penecontemporaneous process that took place in the floodbasin sediments during their prolonged subaerial exposure under a hot and seasonally wet and dry (savanna) climate. The haematitic pigment was derived from the in situ and progressive dehydration of detrital amorphous and poorly crystalline brown hydrated ferric oxide in those sediments which maintained an oxidizing environment and were above the ground-water table during the dehydration process. Sediments which remained in a water-logged state, below the water table, and in association with organic matter, were invariably reduced and lost their iron oxide in solution. Later post-depositional reduction of some red lithologies produced reduction spheres and channels, reduced burrows and vein networks, and the reduced layers immediately underlying the scoured surface at the base of the channel sandstones. Some chemical redistribution of iron contributed to the variegated and mottled horizons of the formation. The mineral composition of adjacent red and drab lithologies is essentially the same except for the haematite constituent. The red average 5.86 ([delta] = 1.09) percent total Fe (as Fe2O3), of, which 3.01 ([delta] = 0.63) percent is as haematite pigment, 1.57 percent Fe2O3 is in a combined form (probably as ferric silicates), and 1 14 ([delta] = 0.57) percent is as FeO. The green average 3.65 ([delta] = 1.81) percent total Fe (as Fe2O3) of which approximately 0.27 percent is as haematite pigment, approximately 1.4 percent Fe2O3 is in a combined form, and 1.77 ([delta] = 1.37) percent is as FeO. In the majority of the green lithologies the free ferric oxide (as haematite or hydrated ferric oxide) was removed in solution during reduction, and at the same time minor amounts of clay matrix were also leached out.</p>

FIRST ARGENTINE MICROFOSSIL BONEBED FROM THE UPPER TRIASSIC MARAYES—EL CARRIZAL BASIN, SAN JUAN PROVINCE

Palaios ◽  
2015 ◽  
Vol 30 (10) ◽  
pp. 743-757 ◽  
Author(s):  
CARINA E. COLOMBI ◽  
RICARDO N. MARTÍNEZ ◽  
GUSTAVO CORREA ◽  
ELIANA FERNáNDEZ ◽  
PAULA SANTI MALNIS ◽  
...  
Keyword(s):  
Upper Triassic ◽  
San Juan ◽  
Fluvial System ◽  
High Concentration ◽  
Fine Grained ◽  
Subaerial Exposure ◽  
Low Degree ◽  
Authigenic Mineral ◽  
Three Stages ◽  
Tooth Marks

Abstract The first Triassic microfossil bonebed found in Argentina is located 80 meters from the top of the Quebrada del Barro Formation in the Marayes-El Carrizal Basin, in the province of San Juan. It consists of specimens from at least 63 individuals from an anomalously high concentration of fossils distributed laterally and vertically in a meter-thick fine-grained deposit. Two new taxa from the genera Sphenodontia and Eucynodontia had previously not been found in Argentine Triassic quarries. The bonebed is preserved in a mudflow deposit interbedded with calcic-Argillisols in the medial-distal zone of a distributary fluvial system (DFS). The accumulation is characterized by small-sized skeletal fragments (skulls, jaws and vertebra; all less than 50 mm), low degree of articulation, variable degrees of subaerial exposure, tooth marks, surface dissolution, and an alkaline authigenic mineral suite. Detailed paleoenvironmental and taphonomic characterization indicate that this accumulation underwent three stages in its taphonomic history: (1) biogenic extrinsic concentration; (2) local transportation and re-deposition by a mudflow on a swampy floodplain; and (3) drying and pedogenesis. Additionally, the deposit highlights biogenic activity as a way to concentrate a paleofaunal assemblage that likely represents the original community, and mudflow deposits from crevasse splays in DFS as a potential facies for microfossil preservation.

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