scholarly journals Siliciclastic sedimentation in the interlude between two Neoproterozoic glaciations, Mirbat area, southern Oman: A missing link in the Huqf Supergroup?

GeoArabia ◽  
2008 ◽  
Vol 13 (4) ◽  
pp. 45-72
Author(s):  
Ruben Rieu ◽  
Philip A. Allen
Keyword(s):  
Arabian Peninsula ◽  
Sedimentary Rocks ◽  
Crystalline Basement ◽  
Coarse Grained ◽  
Shallow Marine ◽  
Fluvial Deposits ◽  
Fine Grained ◽  
Marine Deposits ◽  
Sedimentary Succession ◽  
Late Neoproterozoic

ABSTRACT The Huqf Supergroup in Oman contains an exceptionally well-preserved and complete sedimentary record of the Late Neoproterozoic era, including the oldest components in some of Oman’s hydrocarbon plays. Outcrops of the Huqf Supergroup in northern and central Oman are now well-documented. However, a key succession in the Mirbat area of southern Oman, the Mirbat Group, which includes a stratigraphic interval missing elsewhere in the Arabian Peninsula, remains poorly understood. The <1.5 km-thick Cryogenian (850–635 Ma) Mirbat Group comprises an essentially continuous succession of little-deformed sedimentary rocks containing two glacial intervals separated by c. 1 km of non-glacial marine deposits. The lowermost glacial interval (Ayn Formation) occupies deep paleovalleys incised into crystalline basement. The overlying Arkahawl Formation records at its base a major post-glacial transgression over the previous basin margin and a 300 to 400 m-thick turbidite complex consisting of 1 to 5 km-wide, coarse-grained depositional lobes embedded vertically and laterally in fine-grained distal turbidite fan deposits. Ayn Formation paleovalleys continued to serve as sediment transport routes for the coarse-grained turbidite complexes of Arkahawl times. The turbidite complex deposits gradationally pass up into a c. 500 m-thick unit of distal-marine mudstone and siltstone. The overlying c. 100 m-thick Marsham Formation records highstand deposition and the pulsed progradation of shallow-marine and fluvial deposits over offshore mudstone and siltstone in the approach to a second glaciation, represented by the Shareef Formation. The sedimentary succession described in this paper is believed to largely fill the stratigraphic gap present between the Ghubrah and Fiq formations in the Al Jabal al-Akhdar in northern Oman represented by an unconformity.

scholarly journals Dominant Weathering Profile Assessment of Kebo-Butak Volcanic Rocks in Gedangsari and Ngawen area, Yogyakarta, Indonesia

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Fathan Hanifi Mada Mahendra ◽  
I Gde Budi Indrawan ◽  
Sugeng Sapto Surjono
Keyword(s):  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Coarse Grained ◽  
Residual Soil ◽  
Geological Condition ◽  
Weathering Profile ◽  
Fine Grained ◽  
Degree Pattern ◽  
Weathering Degree ◽  
East West

The Gedangsari and Ngawen area is predominantly composed of volcanic and volcaniclastic sequencesdistributed east – west direction of the northern parts of Southern Mountain. The massive tectonism as well as tropical climatein this region have been producing weathering profiles in varying thickness which inevitably affects thegeotechnical properties. This study aims to assess the dominant weathering profileof the lower part of Kebo-Butak Formation as well as evaluating the distribution of the discontinuity. In order to know the dominant weathering profile and discontinuity evaluation, this study utilizes a total of  26 panels from five stations investigated through a geotechnical data acquisition including the geological condition, weathering zones, joint distribution, and discontinuity characteristics. The result shows four types of dominant weathering profiles in lower part of Kebo-Butak Formation called as dominant weathering profile A, B, C, and D. Profile A, B, C consisted of a relatively identical weathering degree pattern of fresh, slightly, moderately, completely weathered zone with the variation of thicknesses. However, the weathering degree in profile D reached the residual soil degree controlled by more intensive joints. The fine-grained sedimentary rocks also tends to have smaller spacing, shorter persistence, and higher weathering degree of discontinuities as compared to coarse-grained sedimentary rocks.

scholarly journals Luminescence Dating of Fluvial Deposits from the Weser Valley, Germany

2015 ◽  
Vol 42 (1) ◽  
Author(s):  
Julia Roskosch ◽  
Sumiko Tsukamoto ◽  
Manfred Frechen
Keyword(s):  
Late Pleistocene ◽  
Luminescence Dating ◽  
Marine Isotope Stage ◽  
Coarse Grained ◽  
Performance Tests ◽  
Luminescence Signal ◽  
Fluvial Deposits ◽  
Fine Grained ◽  
Infrared Stimulated Luminescence ◽  
Off Time

Abstract Luminescence dating was applied on coarse-grained monomineralic potassium-rich feld-spar and polymineralic fine-grained minerals of five samples derived from fluvial deposits of the Riv-er Weser in northwestern Germany. We used a pulsed infrared stimulated luminescence (IRSL) single aliquot regenerative (SAR) dose protocol with an IR stimulation at 50°C for 400 s (50 μs on-time and 200 μs off-time). In order to obtain a stable luminescence signal, only off-time IRSL signal was rec-orded. Performance tests gave solid results. Anomalous fading was intended to be reduced by using the pulsed IRSL signal measured at 50°C (IR50), but fading correction was in most cases necessary due to moderate fading rates. Fading uncorrected and corrected pulsed IR50 ages revealed two major fluvial aggradation phases during the Late Pleistocene, namely during marine isotope stage (MIS) 5d (100 ± 5 ka) and from late MIS 5b to MIS 4 (77 ± 6 ka to 68 ± 5 ka). The obtained luminescence ages are consistent with previous 230Th/U dating results from underlying interglacial deposits of the same pit, which are correlated with MIS 7c to early MIS 6.

Oxygen, carbon and strontium isotope study of the carbonatitic dolomite host of the Bayan Obo Fe-Nb-REE deposit, Inner Mongolia, N China

1997 ◽  
Vol 61 (407) ◽  
pp. 531-541 ◽  
Author(s):  
M. J. Le Bas ◽  
B. Spiro ◽  
Yang Xueming
Keyword(s):  
Sedimentary Rocks ◽  
Coarse Grained ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Fine Grained ◽  
Dolomite Marble ◽  
Ore Body ◽  
Ore Bodies ◽  
Isotope Study ◽  
Bayan Obo

AbstractThe large Fe-Nb-REE deposit at Bayan Obo is hosted by a dolomite marble within the thrust complex of marbles, quartzites and slates that belongs to the Bayan Obo Formation of mid-Proterozoic age. The dolomite is either a dolomitized sedimentary limestone subsequently mineralized and tectonically thrust and folded, or a dolomite (or dolomitized) carbonatite intrusion with late-stage recrystallization and mineralization that has been subsequently tectonically deformed.O and C isotope data indicate that the sedimentary limestones and dolomites of the Bayan Obo Formation, which occur in the thrust stack together with quartzites and slates, have values of δO c. +20 per mil (SMOW) and δC c. zero. In contrast, the coarser grained facies of the large (0.5 × 10 km) dolomite marble which hosts the REE ore body has δO per mil values between +8 and +12 and δC values between −5 and −3, whereas the finer-grained recrystallized and REE-mineralized dolomite marble which occurs close to the ore bodies has δO between +12 to +16 and δC between −4 and zero. 87Sr/86Sr data confirm this distinction: >0.710 for the sedimentary rocks and <0.704 for the coarse- and fine-grained dolomite marbles.These data are taken to indicate that the large and coarse-grained dolomite was an igneous carbonatite (as borne out by its fenitic contact rocks and trace element geochemistry), and that the finer grained dolomite recrystallized under the influence of mineralizing solutions which entrained groundwater. The stratiform features in the coarse-grained dolomite that are evident in the field are interpreted as tectonic layering.

Pb–Zn occurrences and their Pb-isotopic signatures bearing on metallogeny and mineral exploration—Paleozoic sedimentary rocks, northern Appalachians, Quebec

1988 ◽  
Vol 25 (11) ◽  
pp. 1777-1790 ◽  
Author(s):  
K. Schrijver ◽  
E. Marcoux ◽  
G. Beaudoin ◽  
J. Y. Calvez
Keyword(s):  
Continental Crust ◽  
Mineral Exploration ◽  
Sedimentary Rocks ◽  
Isotope Ratios ◽  
Isotopic Signature ◽  
Coarse Grained ◽  
Pb Isotope ◽  
Isotopic Signatures ◽  
Fine Grained ◽  
Quartz Veins

Galena Pb-isotope ratios of epithermal vein and disseminated sulfide occurrences in the Taconian Orogen and Siluro-Devonian basin cluster around 17.90–18.05 for 206Pb/204Pb and 37.70–38.00 for 208Pb/204Pb. The major source of Pb in most, if not all, occurrences is a fairly common continental crust, a characteristic found in published analyses of Grenville feldspar Pb. A southwest to northeast increase in galena 206Pb/204Pb ratios is ascribed to the supply of several types of detritus from Grenville basement during the Cambro-Ordovician: coarse-grained, K-feldspar-bearing in the southwest, grading into fine-grained phyllitic, and relatively more highly radiogenic in the northeast.Emplacement (i) of Pb–Zn–barite veins and disseminations, commonly of homogeneous crustal Pb-isotopic signature, was late Taconian; (ii) of Pb–Zn–quartz veins, of less homogeneous signature, was post-Taconian; and (iii) of Pb–Zn–carbonate veins, relatively highly radiogenic and commonly homogeneous, was late or post-Acadian. Signatures of the first-mentioned group seem to be most useful in exploration.

scholarly journals A record of deglaciation-related shifting of the proximal zone of a sandur — a case study from the Gwda sandur, NW Poland (MIS 2)

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Mateusz Mleczak ◽  
Małgorzata Pisarska-Jamroży
Keyword(s):  
Structural Features ◽  
Complex Problem ◽  
Coarse Grained ◽  
Fine Grained ◽  
Depositional Processes ◽  
Long Time ◽  
Sedimentary Succession ◽  
Late Weichselian ◽  
Proximal Zone ◽  
Nw Poland

AbstractThe study analyses a 7.5-m-thick sedimentary succession deposited in the largest sandur (the Gwda sandur, a glacial outwash plain) in NW Poland, during the late Weichselian (MIS 2). Although the study site is located in the distal zone of the sandur, its sedimentological features and palaeohydrological parameters reflect the presence of an energetic, powerful environment typical of the proximal zone. Three sedimentary units were recognized in the studied sedimentary succession: (1) lower unit — fine-grained sands with ripple cross-lamination and horizontal lamination; (2) middle unit — gravelly coarse-grained sands and sandy gravels with planar cross-stratification; and, (3) upper unit — sands and gravelly sands with trough cross-stratification. Although the age of deposition of the sandur is accepted to be convergent with that of end-moraines of the same phase, the sediments in the distal zone of the Gwda sandur correlate with an earlier glaciation phase/subphase. Our findings hint at a complex problem: large sandurs such as the Gwda sandur were probably deposited over a long time, and their successions might record the textural and structural features of the proximal subenvironment, even in their distal parts due to deglaciation-related shifting of the proximal zone of a sandur. This paper presents a new approach to analysing the depositional processes in large sandurs, shows a new light on glaciofluvial water supply dynamics of distal parts of sandurs, and may solve several fundamental problems related to the sandur deposition.

Clay mineralogy and geochemistry of early Jurassic sedimentary rocks from the Moezian Platform, northern Bulgaria

Clay Minerals ◽  
2002 ◽  
Vol 37 (3) ◽  
pp. 413-428 ◽  
Author(s):  
E. Hrischeva ◽  
S. Gier
Keyword(s):  
Clay Minerals ◽  
Clay Mineral ◽  
Sedimentary Rocks ◽  
Depositional Environments ◽  
Early Jurassic ◽  
Source Rocks ◽  
Shallow Marine ◽  
Fine Grained ◽  
Depositional Processes ◽  
Mineral Assemblages

AbstractClay minerals in early Jurassic sequences of shales, siltstones and sandstones deposited in non-marine, transitional and shallow marine environments have been examined by X-ray diffraction, electron microscopy and chemical analysis to study the relationship between clay minerals, their environment of deposition and subsequent diagenetic modifications.The inherited clay mineral composition of the fine-grained sediments reflects the influence of climate, relief, source rocks and depositional processes. Inhomogeneous clay mineral assemblages, comprising abundant kaolinite and varying proportions of illite, I-S, chlorite and vermiculite, characterize fine-grained sediments from the non-marine and transitional environments. In shallow marine depositional environments clay mineral assemblages are more uniform, dominated by illite+I-S with minor kaolinite and chlorite.The principal diagenetic process affecting fine-grained sedimentary rocks is the smectite–illite transformation. In sandstones, the authigenic formation of kaolinite, chlorite and illite appears to have been primarily determined by the environment of deposition.

Source terranes for Proterozoic sedimentary rocks in southern British Columbia: Nd isotopic and petrographic evidence

1988 ◽  
Vol 25 (6) ◽  
pp. 824-832 ◽  
Author(s):  
R. A. Burwash ◽  
P. A. Cavell ◽  
E. J. Burwash
Keyword(s):  
British Columbia ◽  
Sedimentary Rocks ◽  
Crystalline Basement ◽  
Main Body ◽  
Residence Times ◽  
Stratigraphic Unit ◽  
Fine Grained ◽  
Southern Alberta ◽  
Windermere Supergroup ◽  
Basal Conglomerate

Quartz arenites of the Fort Steele Formation, the lowest exposed stratigraphic unit of the Purcell Supergroup, have Nd crustal residence times (Tcr) of 2.61–2.63 Ga. These overlap the low end of the Tcr range of the polymetamorphic Kenoran–Hudsonian basement of southern Alberta and southwestern Saskatchewan. The Tcr values of overlying fine-grained Purcell rocks average 2.0 Ga.Near Lake Windermere, the basal Toby conglomerates of the Windermere Supergroup, apparently derived from underlying Purcell strata, have Tcr values of 1.98 and 2.03 Ga. Stratigraphically higher argillite and arkoses range from 2.35 to 2.54 Ga. This higher range indicates contributions from a source terrane different from the main body of the Purcell Supergroup.Our interpretation of events in the East Kootenay area is that early Purcell sedimentation (Fort Steele Formation) was derived from reworking of the crystalline basement of the Alberta shelf as the Beltian Sea transgressed. As the basin deepened, it was filled by fine-grained turbidites from a distal southern or southeastern source. Later Purcell strata have more complex paleocurrent direction patterns but relatively uniform Tcr values similar to those of the earlier turbidites. Following the East Kootenay orogeny, the basal conglomerate of the Windermere Supergroup (Toby Formation) consisted dominantly of locally derived clasts. These Purcell-derived strata grade upward into arkosic rocks with an admixture of Archean detrital material, probably from a proximal eastern source.

scholarly journals Sedimentological characterization of the quaternary deposits in the region between Marília and Presidente Prudente, São Paulo State, Brazil

2008 ◽  
Vol 61 (3) ◽  
pp. 343-356 ◽  
Author(s):  
Alethéa Ernandes Martins Sallun ◽  
Kenitiro Suguio
Keyword(s):  
Sedimentary Rocks ◽  
Sao Paulo ◽  
Heavy Minerals ◽  
Coarse Grained ◽  
São Paulo ◽  
Fine Grained ◽  
Paulo State ◽  
Grain Sizes ◽  
São Paulo State ◽  
Bauru Group

Sedimentologic characterization and provenance studies of quaternary colluvial deposits (9±1 to 980±100 ky B.P. - dated by luminescence) were based on textural and mineralogical analyses. These deposits occur extensively between Marília and Presidente Prudente (São Paulo State, Brazil), superimposed on the Bauru Group sedimentary rocks or the Serra Geral Formation basaltic rocks, both of Cretaceous age. They are distributed irregularly throughout the study area and are studied by sedimentologic and morphologic methods. These deposits are composed of very fine to coarse-grained unconsolidated sands, mostly constituted by quartzose monocrystalline grains reddened by iron oxide and hydroxide impregnation. Analyses of grain sizes indicated that total granulometric distributions are richer in the clay fraction than in the sedimentary rocks located. Non-micaceous transparent heavy minerals studied microscopically in fine-grained as well as in very fine-grained sands showed that zircon, tourmaline, staurolite and rutile are present in all the samples. Differences in grain sizes among the colluvial deposits and the Bauru Group sedimentary rocks are attributable to pedogenetic processes.

scholarly journals Ediacaran and Cambrian rocks on Scatarie Island and nearby Hay Island, Avalonian Mira terrane, Cape Breton Island, Nova Scotia, Canada

2020 ◽  
Vol 56 ◽  
pp. 257-279
Author(s):  
Sandra M. Barr ◽  
Chris E. White ◽  
Sören Jensen ◽  
Teodoro Palacios ◽  
Deanne Van Rooyen
Keyword(s):  
Nova Scotia ◽  
Geographical Distribution ◽  
Detrital Zircon ◽  
Sedimentary Rocks ◽  
Trace Fossils ◽  
Island Formation ◽  
Cape Breton Island ◽  
Fine Grained ◽  
Cape Breton ◽  
Late Neoproterozoic

Scatarie Island and adjacent Hay Island, located 2 km east of the eastern tip of the Avalonian Mira terrane of southern Cape Breton Island, Nova Scotia, contain a succession of epiclastic and other sedimentary rocks of inferred Ediacaran to Cambrian age. The age assignment was based previously on lithological comparison with the Main-à-Dieu Group and overlying Bengal Road and MacCodrum formations of the Mira River Group. Detrital zircon grains from two sandstone samples from the Bengal Road Formation yielded typical Avalonian detrital zircon spectra with middle to late Neoproterozoic, Meso- to Paleoproterozoic (1300–2200 Ma) and Neoarchean ages. They indicate maximum depositional ages of 532.4 ± 4.2 Ma and 525.4 ± 2.4 Ma from essentially the same stratigraphic level, consistent with the interpretation that the rocks are Cambrian. The Bengal Road Formation also yielded scarce organic-walled microfossils including an acanthomorphic acritarch identified as Polygonium sp., also consistent with Cambrian age. The fine-grained siliciclastic succession on Hay Island, tentatively attributed to the MacCodrum Formation, yielded trace fossils, including Teichichnus isp. and Gyrolithes scintillus, that confirm Cambrian age. The Hay Island Gyrolithes scintillus expands the geographical distribution of this ichnospecies, previously known mainly from the Chapel Island Formation of Newfoundland, and represents a younger occurrence.

Correlation between dislocation, grain boundary and interface of duplex SS in stress corrosion cracking(SCC)

1990 ◽  
Vol 48 (4) ◽  
pp. 928-929
Author(s):  
Wang Zheng-fang ◽  
Z.F. Wang
Keyword(s):  
Stainless Steel ◽  
Thermal Cycle ◽  
Secondary Phase ◽  
Corrosion Cracking ◽  
Coarse Grained ◽  
Test Environment ◽  
Fine Grained ◽  
Evaluation Test ◽  
Welding Thermal Cycle ◽  
Micro Analysis

The main purpose of this study highlights on the evaluation of chloride SCC resistance of the material,duplex stainless steel,OOCr18Ni5Mo3Si2 (18-5Mo) and its welded coarse grained zone(CGZ).18-5Mo is a dual phases (A+F) stainless steel with yield strength:512N/mm2 .The proportion of secondary Phase(A phase) accounts for 30-35% of the total with fine grained and homogeneously distributed A and F phases(Fig.1).After being welded by a specific welding thermal cycle to the material,i.e. Tmax=1350°C and t8/5=20s,microstructure may change from fine grained morphology to coarse grained morphology and from homogeneously distributed of A phase to a concentration of A phase(Fig.2).Meanwhile,the proportion of A phase reduced from 35% to 5-10°o.For this reason it is known as welded coarse grained zone(CGZ).In association with difference of microstructure between base metal and welded CGZ,so chloride SCC resistance also differ from each other.Test procedures:Constant load tensile test(CLTT) were performed for recording Esce-t curve by which corrosion cracking growth can be described, tf,fractured time,can also be recorded by the test which is taken as a electrochemical behavior and mechanical property for SCC resistance evaluation. Test environment:143°C boiling 42%MgCl2 solution is used.Besides, micro analysis were conducted with light microscopy(LM),SEM,TEM,and Auger energy spectrum(AES) so as to reveal the correlation between the data generated by the CLTT results and micro analysis.

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