Hellenic Trench sedimentation: An approach using terrigenous distributions

Feldhausen, Peter H.; Stanley, Daniel Jean

doi:10.1016/0025-3227(80)90003-1

Cited by 6 publications

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“…These three fine-grained types, in some instances, have been confused with betterdefined facies such as mud turbidites, hemipelagic muds and sapropels with which they are sometimes associated and may be genetically related. The more obvious compositional and textural differences between these mud types are obscured as a result of homogenization from the continued redeposition to more distal sites and incorporation of pelagic components during transport (Vittori, 1978;Feldhausen & Stanley, 1980). Only with a detailed petrographic and X-radiographic methodology is it possible to identify the sequence of transport episodes responsible for displacing sediment between shelf-inner trench slope settings and deep distal sectors.…”

Section: J Stanley and A Maldonadomentioning

confidence: 99%

“…It bears on the problem of identifying types and distributions of muds, and on their dispersal in submarine trench settings. Sedimentation of the sand-size terrigenous fraction, which accounts for a relatively small pro- (cruise 172, 1975) 32 37" 36.5' 20" 246' 3345 378 33 37" 25.6' 20" 18.2' 3820 339 34 37" 21.5' 20" 19.2' 4060 694 35 37" 22.9' 20" 21-3' 4140 609 36 37" 284' 20" 344' 4147 690 37 37" 38.2' 20" 35.3' 1200 215 R/V Marsili (Hellenic cruise, 1976) portion of the Late Quaternary cores, is discussed elsewhere (Feldhausen & Stanley, 1980). The small, confined sector west and south of the Peloponnesus in the eastern Mediterranean (Fig.…”

Section: Introductionmentioning

confidence: 99%

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Depositional models for fine‐grained sediment in the western Hellenic Trench, Eastern Mediterranean

Stanley

Maldonado

1981

Sedimentology

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Sediment in tectonically active, topographically restricted settings of the western Hellenic Arc, eastern Mediterranean, consists primarily of clayey silt and silty clay. Failure of metastable sediment temporarily stored on relatively steep slopes is triggered by earthquake tremors and eustatic oscillations. Redeposition of these materials by gravitative transport has resulted in markedly different lithofacies from site to site. Most piston cores include three Late Quaternary stratigraphic units that can be correlated with sections in other parts of the eastern Mediterranean; numerous radiocarbon-age determinations enhance the correlation.Seven fine-grainedsediment types are identified in cores fromeight dist inct depositional environments. Some muds are closely related to specific environments (slump and debrisflow deposits on slope and high-relief environments), or to time (well luminatedmud during the latest Pleistocene-mid-Holocene), or to both (uniform and faintly laminated muds restricted to trench basins), Turbiditic and hemipelagic muds are common throughout the study area. Mud distribution patterns correlate closely with calculated sedimentation rates.We propose two depositional models for these sediments. The first emphasizes downslope transformations resulting in progressively reduced flow concentration during transport : from slump and debris flow+turbidity current+low density turbidity current or turbid layer mechanisms. The distal endmember deposits settling from low concentration flows are thick, rapidly emplaced, fine-grained uniform muds closely associated with faintly laminated muds. These were ponded in flat trench basinplains. Planktonic and terrigenous fractions in the turbiditic, finely laminated and uniform muds record mixing of materials of gravitative and suspension origin during redeposition. This sequence prevails under conditions of minimal stratification of water masses, as characterized by the present Mediterranean.In the second model developed for conditions of well-developed water mass stratification, well laminated rather than uniform mud prevails as the end product of low concentration flows. These very finely laminated and graded muds record particle-by-particle settling from detached turbid layers concentrated along density interfaces; they include material from turbid layers complemented by the normal 'rain' of pelagic material. Stratification barriers resulted in region-wide distribution of such deposits, in both slope and trench environments. la couverture Plio-Quaternaire au niveau des pentes et des fosses HellPniques de PPloponnBse (CrPcc). Unpublished Thesis, UniversitC Paul Sabatier, Toulouse, 194 pp. 324-328. NOTE ADDED INPROOFThe name unifte is applied t o the nearly structureless, often thick, layers of clayey silt and silty clay that are formed by the uniform and faintly laminated mud facies described in this study. Such deposits generally appear but are not truly compositionally homogeneous and show a subtle fining-upward trend, and are deposited by gravity flow tra...

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Section: J Stanley and A Maldonadomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Depositional models for fine‐grained sediment in the western Hellenic Trench, Eastern Mediterranean

Stanley

Maldonado

1981

Sedimentology

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“…Successive gravitative events apparently result in size-sorting effects and, consequently, in changes downslope in the proportions of mineralogical components. Repeated redeposition may explain, for example, the downslope increase in clastic aggregates and planktonic tests relative to the sand-size terrigenous fraction (Feldhausen and Stanley, 1980). The increased proportion of attapulgite (palygorskite) downslope in the Kithera-Antikithera Trench is still further evidence of gravity-induced processes involving slope erosion (Stanley, Blanpied, and Sheng, 1981).…”

Section: Implications Of Study and Conclusionmentioning

confidence: 98%

“…The diminished basinward proportions of sarid and compositional homogenization of fine-grained sediments in the distally located cores (Figure 1) are accounted for by a barrier or dam effect, resulting from the complex topographic setting. This complexity induces preferential entrapment of coarser fractions in slope-perched catchment basins (Vittori, 1978: 44;Feldhausen and Stanley, 1980;Feldhausen et al, 1981). The major evidence that sediment has been carried into Hellenic Trench basins via submarine valleys is the presence of low-gradient basin aprons localized along some base-of-slope sectors (Figure 13).…”

Section: Implications Of Study and Conclusionmentioning

confidence: 99%

“…In this manner, coarse material is selectively entrapped in submarine valleys, perched slope basins, and depressions in the cobblestone terrain. Line drawings of selected 3.5 kHz profiles (on the right) from the Zakinthos- samples from these aprons include reworked shallow water microfossils and volcanic materials, and relatively important contents of terrigenous fractions of both silt and sand size (Feldhausen and Stanley, 1980). Some unifites, particularly those in the Zakinthos-Strofadhes Trench basin, were probably emplaced by canyon-derived turbidity currents spreading across trench basins.…”

Section: Implications Of Study and Conclusionmentioning

confidence: 99%

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Uniform Mud (Unifite) Deposition in the Hellenic Trench, Eastern Mediterranean

Blanpied¹,

Stanley²

1981

Smithsonian Contributions to the Marine Sciences

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Christian Blanpied and Daniel Jean Stanley. Uniform Mud (Unifite) Deposition in the Hellenic Trench, Eastern Mediterranean. Smithsonian Contributions to the Marine Sciences, number 13, 40 pages, 15 figures, 2 tables, 1981.-Unifites are nearly structureless, often thick, layers of clayey silt and silty clay that appear compositionally homogeneous and generally show a subtle finingupward trend. Formed by uniform and faintly laminated muds, unifites are deposited from rapidly emplaced single gravity-flow events. Along the Hellenic Arc, unifites are restricted to small trench basins and interpreted as an endmember gravity-emplaced facies. Unifites are not truly homogeneous and the petrological distinctions observed are closely related with the trench basin depositional site relative to steep margins bounding the trench plain. The faintly laminated portions of unifites contain a higher silt content; the uniform mud portions are slightly better sorted and display an upward increase of planktonic tests. The sand fraction is dominated by clastic aggregates eroded from older margin sediments; unifites also comprise a large silt-size nannofossil content (including reworked forms). The increased uniformity basinward of unifites records deposition from turbidity current-related flows of diminished concentration that spread over large areas of a flat trench floor. Faint laminae may be related to phases of flocculation and depositional sorting of the sediment load during transport, and to the hydraulic jump affecting a flow upon its arrival on a near-flat basin floor. The slower-moving tail releases the uppermost nonlaminated, graded unifite mud term. The thickness of Hellenic unifites is a function of entrapment of moderate amounts of material in small trench plains. The homogenization process essential for unifite deposition involves relief bypass, i.e., the preferential entrapment of coarser or denser fractions in slope depressions, while finer or less dense particles are transported further downslope across irregular seafloor features. Unifite deposition records the interplay of: (1) complexity of dispersal paths and accessibility of sediment to the trench basin, (2) redepositional processes, grain-support mechanisms and gravityinduced flow characteristics, (3) type of material transported, (4) extent of textural segregation and compositional sorting during flow, (5) slope relief bypassing process, and (6) selective entrapment of essentially fine-grained particles in the more distal trench catchment basins. Mediterranean unifites can serve to interpret uniform mud facies on both active and passive margins and in the rock record. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: Seascape along the Atlantic coast of eastern North America. Library of Congress Cataloging in Publication Data Blanpied, Christian. Uniform mud (unifite) desposition in the Hellenic trench, eastern Mediterranean. (Smithsonian contr...

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Mediterranean Seafloor Features: Overview and Assessment

Vanney¹,

Gennesseaux²

1985

Geological Evolution of the Mediterranean Basin

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Hellenic Trench sedimentation: An approach using terrigenous distributions

Cited by 6 publications

References 6 publications

Depositional models for fine‐grained sediment in the western Hellenic Trench, Eastern Mediterranean

Depositional models for fine‐grained sediment in the western Hellenic Trench, Eastern Mediterranean

Uniform Mud (Unifite) Deposition in the Hellenic Trench, Eastern Mediterranean

Mediterranean Seafloor Features: Overview and Assessment

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