scholarly journals Concerning the Microdiamonds and Cosmic Spherules from Middle Pleistocene Selenge River Basin in North Mongolia

2017 ◽  
Vol 1 (1) ◽  
Keyword(s):  
River Basin ◽  
Practical Interest ◽  
Flood Plain ◽  
Middle Pleistocene ◽  
Alluvial Deposits ◽  
The North ◽  
River Terraces ◽  
Cosmic Spherules ◽  
Alluvial Terraces ◽  
North And South

This paper concerns deals with new discovery of microdiamonds and cosmic spherules from Middle Pleistocene Selenge river basin by the example of the Teel and Khukh Ereg terrace alluvial terraces. The Teel and Khukh Ereg alluvial terraces are located at the north and south edges of the Selenge river (Fig.1), at the base of mountain Namnan uul (Fig.2). These terraces are those whose cusp and bench entirely composed of alluvial sediments of Middle Pleistocene age [1]. This indicates that the Selenge river has a long history of development, had time to develop a flood plain and to deposit alluvium, through which it cut subsequently and north and south behind as a Teel and Khukh Ereg terraces [2]. Alluvium studies may be of great practical interest because in some areas, river terraces are veritable treasure-troves of economic minerals. With river terraces are associated most placer deposits of such important economic minerals as gold, platinum, diamond, etc. Numerous engineering projects, an example, bridges (Kherlen, Tuul, Selenge, Orkhon, Baidrag, Tui, Zavkhan, Delger Muren, etc.), dams and hydropower plants (Durgun Nuur, Ulaan Boom) are built on alluvial deposits. Hence the need to know all the essential features of the geostructure of river terraces. Just our investigation of the Selenge river terraces in 2006-2010 and 2014 gave possibility to discover the placer diamonds within the Teel and Khukh Ereg alluvial terraces for the first time in Mongolia [3,4].

scholarly journals SOLONSKE SECTION AND THE PERSPECTIVES OF THE STUDY OF PLEISTOCENE CARPATHIAN FORELAND

2019 ◽  
pp. 73-100
Author(s):  
Roman Hnatiuk ◽  
Igor Papish
Keyword(s):  
Field Study ◽  
Key Words ◽  
Middle Pleistocene ◽  
Buried Soils ◽  
Iron Compounds ◽  
Main Attention ◽  
Alluvial Deposits ◽  
River Terraces ◽  
The Village ◽  
Made In

The article presents the results of the field study of the two artificial outcrops of the Pleistocene deposits, which are located in the suburbs Solonske near Drohobych city. Outcrops (careers) are located within the terrace of the Tysmenytsia River. The height of the terrace is about 50 m above the river level and changes along the distance from the mountains. The main attention in the article is paid to the study of the structure of the upper (covering) stratum of the terrace with a thickness of about 26 m, and also to the characteristics of its consolidated stratigraphic section. The basis of this stratum consists of the layers of non-carbonate loams and clays. They are more or less enriched of iron compounds and gleyed. Between them there are four horizons of buried soils of the interglacial and interstadial rank. Based on the observations made in the field, it was found that the sediments of the covering stratum have mainly river origin. The conditions of their accumulation, as well as the conditions for the formation and transformation of ancient soils, are considered; eight pre-Holocene lito- and pedostratigraphic layers of different rank are singled out. The division of the covering stratum of the terraces into three main layers is sub¬stan¬tiated, which is equivalent to the stratigraphic units of the glacial and interglacial rank. Comparison of the Solonske section with other sections of the similar height terraces, in particular with well-known outcrops near the village Dubrivka (section Dubrivka) gives grounds to assume that the formation of a local terrace occurred during the Marine Isotopic Stages 12 to 10. Consequently, the Solonske section represents a short strati¬gra¬phic interval of the Middle Pleistocene (not the three main Pleistocene units as stated in the results of its previous study). It can be the basis for studying only a few (two to three) horizons of the glacial/interglacial rank. At the same time, it is potentially a very impor¬tant key section of the Solonske (Dubrivska, Dovhivska, Varnytska) terrace of the Pre-Dniester. The studying of Solonske outcrops makes it necessary to revise the popular notions about the origin and the age of the so-called covering stratum of the river terraces of the Carpathian Foreland and Podolian Pre-Dniester, its stratigraphic filling and significance. Key words: alluvial deposits; terraces; soil-loess sequence; Middle Pleistocene; Dniester valley; Carpathian Foreland; Solonske section.

scholarly journals Evolution of the Bystrzyca River valley during Middle Pleistocene Interglacial (Sudetic Foreland, south-western Poland)

2020 ◽  
Vol 12 (1) ◽  
pp. 1679-1703
Author(s):  
Dariusz Krzyszkowski ◽  
Lucyna Wachecka-Kotkowska ◽  
Marcin Krawczyk
Keyword(s):  
Distal Part ◽  
System Development ◽  
River System ◽  
River Valley ◽  
Oxbow Lake ◽  
Middle Pleistocene ◽  
Alluvial Deposits ◽  
The North ◽  
Study Results ◽  
Tectonic Movements

AbstractThe article depicts the problem of river system development during the Middle Pleistocene Interglacial in the Bystrzyca River Valley (Sudetic Foreland, south-western Poland). Ten research sites located within the Świdnica Plain are presented, in which the structural, grain size (granulometry), petrographic, quartz grain morphoscopy, and heavy mineral analyses were carried out. The study results show the formation of piedmont fan deposits 2–8 km to the NE of the Sudetic Marginal Fault. The location of the fluvial deposits between the Sanian and Odranian tills indicates that they were deposited during the Holsteinian Interglacial (Krzczonów Formation, Mazovian; see Table 1). According toxthe lithofacies analysis, vast alluvial plains, composed of angular gravel grains in the south and of sands in the north, were deposited in the Sudetic Foreland in the environment of a very dynamic river. They are covered with a discontinuous layer of Odranian till. The petrographic spectrum shows 90–99% of local rocks, namely, Sudetic porphyry, Sowie Mts Gneiss and milky quartz, and 1–10% of Scandinavian rocks. In the proto-Bystrzyca river system, the existence of an oxbow lake in the distal part of the Krzczonów fan has been proved, which was developing at the end of the Holsteinian Interglacial. The continuity of the alluvial deposits is interrupted in the vicinity of Świdnica due to both the tectonic movements and the formation of the narrow tectonic graben of Roztoka–Mokrzeszów.

IV.—The Post-Pleistocene Flora and Fauna of Central England

1910 ◽  
Vol 7 (12) ◽  
pp. 542-553
Author(s):  
A. R. Horwood
Keyword(s):  
Fresh Water ◽  
The Other ◽  
Central Position ◽  
The South ◽  
Alluvial Deposits ◽  
Drainage Systems ◽  
River Drainage ◽  
The North ◽  
The One ◽  
North And South

The central position of Leicestershire gives it not only a peculiar relationship in regard to river-drainage, streams radiating from its plateau-frontier on the one hand to the north, flowing into the Humber, and on the other to the south into the Bristol Channel, separated alone by a now comparatively insignificant divide in the neighbourhood of Lutterworth. Also the very fact that this divide is given, by the otherwise lowland character of the tract to the north and south, a barrier-like aspect, renders it highly probable that the flora and fauna in this basin-like area is more or less homogeneous. That it has been uniform in character, no doubt from pre-Glacial times, when doubtless the existing drainage systems (though probably still more ancient fundamentally) received their most recent stamp, having been little modified (except in depth or width) during Glacial or later times. For this purpose we must needs summarize all that is known as to the occurrence of plants or land and fresh water Mollusca in post-Pleistocene alluvial deposits.

Alluvial Terracing in a Falling-stage Braidplain: the Lower Cretaceous Cadomin Formation, West-central Alberta, Canada

2019 ◽  
Vol 89 (8) ◽  
pp. 701-727 ◽  
Author(s):  
Michael F. Johnson ◽  
Robert W. Dalrymple
Keyword(s):  
Lower Cretaceous ◽  
Sediment Supply ◽  
Alluvial Deposits ◽  
Western Canada Sedimentary Basin ◽  
Exceptional Preservation ◽  
Base Level ◽  
The North ◽  
West Central ◽  
Alluvial Terraces ◽  
Canada Sedimentary Basin

Abstract The Lower Cretaceous Cadomin Formation in the Western Canada Sedimentary Basin is a thin, regionally extensive, conglomeratic fluvial deposit that accumulated over many million years on the sub-Cretaceous unconformity. Based on a dataset of approximately 50 cores and 750 wireline well logs from west-central Alberta, detailed isopach mapping of the overlying deposits reveals the presence of a complex, terraced paleo-topography on the top of the Cadomin Formation, consisting of six terrace levels in the study area. These terraces flank a series of north–south valleys that feed into a larger east–west valley to the north of the study area. This larger valley is also bordered by terraces that step downward to the north. The gradients of the north–south valley thalwegs are steeper than the flanking terraces, indicating that each terrace is diachronous and was most likely formed by the headward migration of knickpoints generated by episodic incision of the trunk valley. This paleo-topography formed during a prolonged period of falling base level caused by unroofing of the adjacent orogen. Thus, the Cadomin Formation represents a falling-stage systems tract. The deposits underlying each terrace consist mainly of channel-thalweg and braid-bar deposits. Preservation of full channel-bar successions in many terraces is consistent with terrace abandonment as incision resumed following a period of mild aggradation. Terrace abandonment is also indicated by the presence of a capping layer of wind-blown silt. Pedogenic alteration of this loessite is greatest on the highest terraces and extends to considerable depths, indicating the existence of a significant hiatus at the top of the Cadomin Formation. This surface, which lies above falling-stage deposits, should be used as the sequence boundary, if the sequence boundary is thought to coincide with the time of lowest base level. This surface, although its formation was diachronous, represents a real landscape surface, unlike the composite erosion surface beneath the Cadomin Formation (i.e., the sub-Cretaceous unconformity). The alternation of incision and aggradation that generated the terraces was probably the result of allogenic fluctuations in sediment supply caused by climate cycles, as was the case for analogous Quaternary terrace staircases. Downstepping alluvial terraces are a viable mechanism for the progradation of alluvial gravels long distances from a mountain belt during periods of basin uplift, and may explain the relatively thin, but areally extensive, alluvial sandstone and conglomerate sheets that are common at major unconformities in the stratigraphic record. We suggest that signs of subtle terracing may have been overlooked in similar sheet-like alluvial deposits elsewhere, although they can be removed by erosion during shoreline transgression or by later fluvial-channel migration. In the case of the Cadomin Formation, the exceptional preservation of the terraces is likely due to a combination of the difficulty of eroding the conglomerate and indurated loessite cap, and of the low-energy nature of floodplain sedimentation in the overlying Gething Formation.

PROBLEMS OF DIFFERENTIATION AND CORRELATION OF ALLUVIAL DEPOSITS OF THE NEO-PLEISTOCENE IN THE LOWER OB REGION

2021 ◽  
pp. 18-27
Author(s):  
I. D. Zolnikov ◽  
◽  
A. A. Anoykin ◽  
A. V. Postnov ◽  
A. V. Vybornov ◽  
...  
Keyword(s):  
River Sediments ◽  
Flood Plain ◽  
Middle Pleistocene ◽  
Interglacial Period ◽  
Pleistocene Glaciation ◽  
Pleistocene Glaciations ◽  
Alluvial Deposits ◽  
Glacier Ice

The Upper Neo-Pleistocene alluvial deposits lie in a close hypsometric position in outcrops of the Lower Ob Region right bank. Their top usually does not rise above the level of 5 m above the tow-path edge. At the same level, glacial erratic masses of the Middle Pleistocene alluvium were recorded in a number of areas. The height of the 1st and 2nd sites of terraces (on average from 5 to 10–15 m) depends on the thickness of subaerial deposits overlapping the alluvium. The 3rd terrace above flood-plain of the Bolshaya (Big) Ob has no geomorphological expression, since the alluvium of the first Late Neo-Pleistocene interglacial period without ablation is drape overlain by parallely bedded precipitates of the glacier-ice-blocked lake of the first Late Neo-Pleistocene glaciation. Thus, the height of sites of terraced surfaces does not directly correlate with the age of their alluvial basement. Therefore, the geomorphological method for differentiation of river sediments is not effective for this region. In addition, the problems of differentiation and correlation of alluvial deposits of the Lower Ob Region right bank are complicated by the presence of fluvioglacial incisions of deglaciation stages of the Middle Neo-Pleistocene and Upper Neo-Pleistocene glaciations.

Sign in / Sign up

Export Citation Format

Share Document