Theoretical post-glacial sedimentation rates for a semi-enclosed sea; example of the Kieler Bucht, Western Baltic

The theoretical rates of deposition for fine sediments over the last 10 ka have been deduced and plotted for the Kieler Bucht. Assumptions are that the bay has remained as a closed sedimentary system, and that the fine sediments deposit in water deeper than 10 m. A sharp peak of sedimentation activity is indicated between 7.5 and 8.5 ka B.P. with low rates prior to 9.5 ka and since 6 ka. Comparison of rates obtained from dated cores extracted from different parts of the Kieler Bucht with the theoretical curve shows general conformity, and confirms that peak sedimentation rates exceeding 3 mm/a, as averaged over 100–200 years, occurred between 8 and 9 ka, with the suggestion of a minor activity peak between 3 and 4 ka. The overall consistency supports the view that the bay has acted essentially as a closed sedimentary basin during the Holocene marine transgression and subsequently.     

Late Pleistocene fans and terraces in the Majes valley, southern Peru, and their relation to climatic variations

This study investigates the connection between sediment aggradation, erosion and climate in a desert environment of the Majes valley, southern Peru. Luminescence dating of terraces and fans shows that sediment aggradation correlates with wet time intervals on the Altiplano, suggesting a climatic influence on the aggradation–degradation cycles. Major periods of aggradation occurred between ~110–100, ~60–50 and 12–8 ka. More precipitation in the Majes catchment resulted in increased erosion and transportation of sediment from the hillslopes into the trunk river. As a result, the sediment loads exceeded the transport capacity of the Majes River and aggradation started in the lower reaches where the river gradient is less. Depletion of the hillslope sediment reservoirs caused a relative increase in the capacity of the trunk river to entrain and transport sediment, resulting in erosion of the previously deposited sediment. Consequently, although climate change may initiate a phase of sediment accumulation, degradation can be triggered by an autocyclic negative feedback and does not have to be driven by climatic change.     

Distribution of quartz in late Quaternary Atlantic sediments in relation to climate

The distribution of quartz in the surface sediments of the Atlantic Ocean reflects derivation from continents by means of rivers, wind, ice, and coastal erosion. Enrichment of quartz thus supplied has occurred in some deep basins of especially the southern high latitudes from winnowing of finegrained clays by bottom currents. Although similar modes of quartz transport may have operated both during the Holocene and the last glacial maximum (18,000 yr B.P.), significant differences in the intensity of transport and in the locii of deposition, which are attributable to climatic variations during these times, exist in some areas of the Atlantic. In Holocene sediments of the eastern equatorial Atlantic, a band of high percent quartz exists directly off the present Saharan Desert and Sahel region and reflects the trade-wind transport of dusts from these arid and semiarid regions. During the last glacial maximum (18,000 yr B.P.), this high quartz band expanded southward by about 8° of latitude. This expansion was caused not only by the southward expansion of aridity and desert dunes but also by the southward migration of the northerly belt of trade winds during the last glaciation. Relatively high abundances and accumulation rates of quartz during the last glaciation suggest higher intensities of trade winds during that time compared to the Holocene. In the North Atlantic, the abundances of quartz in Holocene sediments are high adjacent to Greenland-Iceland and in the areas off Newfoundland-Labrador, and gradually decrease toward the central areas. The polar front and limit of sea-ice melting are at present confined to the northern part of the North Atlantic. The ice-rafting of quartz grains is, therefore, effective in the areas adjacent to Greenland and to some extent off Labrador causing high abundances in these areas. In contrast to this, during the last glaciation, the quartz abundances and accumulation rates are high in the central areas of North Atlantic around 45°N and decrease toward Greenland-Newfoundland. The migration of the polar front to as far south as 45°N and the consequent southward migration of sea-ice melting and ice-rafting during the last glaciation apparently caused this change in distribution. In addition to ice-rafting at present, wave or current reworking of relict glacial-marine detritus may have caused the high abundance of quartz in the surface sediments off Newfoundland-Labrador. In 18,000 yr B.P. sediments of the Norwegian Sea, the area of high percent quartz (>10%) is more extensive than that in Holocene sediments. This reflects the greater influence of ice-rafting or glacier activity in the sediment dispersal in the Norwegian Sea during the last glacial times.     

The morphology and late Quaternary paleogeomorphology of the continental shelf off Sydney,NSW

Shallow seismic-reflection profiling and proton-precession magnetometry have been conducted over the continental shelf off Sydney between Broken Bay (in the north) and Bate Bay (in the south) as well as over part of the upper continental slope in the area east of the coastline between Narrabeen and Port Hacking. In this area, four major paleodrainage channels incise the bedrock, within the coastal estuaries and on the inner and mid-shelf:

1. the Hawkesbury paleo-watercourse, which is joined offshore by four lesser paleochannels, that we call the Newport, Mona Vale, Narrabeen and Long Reef paleo-watercourses;

2. the Parramatta paleo-watercourse, which is joined by the Bondi paleo-watercourse;

3. the Botany paleo-watercourse and

4. the Georges paleo-watercourse, which is joined under the Kurnell Peninsula land isthmus by the Cooks paleo-watercourse, and then by the Hacking paleo-watercourses in Bate Bay.

Of these paleodrainages, only that of the Hawkesbury River has discernible expression at depths >120 m, the sea-level low and inferred paleo-shoreline of the Last Glacial Maximum (LGM) at ca 20 ka. Some of the lesser paleo-watercourses are manifested only at depths shallower than the ?120 m paleo-shoreline and include those of the Maroubra paleo-watercourse and the combined Manly/North Head paleo-watercourses. Paleochannels detected below the LGM shoreline are those of:

• the ancestral Hawkesbury River;

• the minor Peak paleo-watercourse east of Coogee, which is discernible at depths shallower than the ?100 m isobath and is maintained to depths greater than ?210 m; and

• the minor Island paleo-watercourse whose head terminates at ～?140 m east of Bronte, lies entirely below the LGM paleo-shoreline, and can be traced to a depth of ?260 m.

Based on the paleotopographic and sediment-infill geophysical records obtained, 10 stages in the evolution of the paleo-watercourses are proposed.     

The subfossil seals of Finland and their relation to the history of the Baltic Sea

The occurrence of seals in the Finnish prehistoric fauna and in the Baltic since the end of the last glaciation is discussed on the basis of subfossil remains in refuses at cultural sites, and stray finds. The species represented are the harp ( Phoca groenlandica Müller), the ringed seal ( Phoca hispida Schreb.), and the grey seal ( Halicoerus grypus (Fabr.)), of which the latter two are native in the recent fauna, whereas the former has since become extinct in the Baltic. The earliest seals, which probably immigrated to the Yoldia Sea, were ringed seals, whereas the subfossil harp seals are solely found in sediments of the Litorina Sea stage.     

Dissolution rates of minerals and their relation to surface morphology

Experimentally observed dissolution rates of minerals in an aqueous solution are determined by surface reaction rates, mass transport by molecular diffusion through a diffusion boundary layer (DBL) and the morphology of the mineral’s surface. By solving the transport equation in the presence of a diffusion boundary layer for surfaces containing open pores their contribution to the observed dissolution rates can be quantified. Furthermore dissolution rates are calculated for fractal surfaces. A general solution is given. Two extremes are discussed. If the surface controlled rate constant k is small compared to the mass transport constant k_t = D/ε (ε thickness of DBL, D coefficient of diffusion), the rates are surface controlled and the entire surface contributes to the observed dissolution rate. In this case rates must be normalized to the B.E.T.-surface area. When k ? k_t the observed rates are limited by diffusion and information on k cannot be obtained. In intermediate cases a careful analysis is required. If ink bottle pores are present their contribution to the observed rates can be neglected and rates must be normalized to the geometrical envelope surface area, although in such cases the B.E.T.-surface area can be much larger.     

Deformation patterns of upper Quaternary strata and their relation to active tectonics,Po Basin,Italy

Despite increased application of subsurface datasets below the limits of seismic resolution, reconstructing near‐surface deformation of shallow key stratigraphic markers beneath modern alluvial and coastal plains through sediment core analysis has received little attention. Highly resolved stratigraphy of Upper Pleistocene to Holocene (Marine Isotope Stage 5e to Marine Isotope Stage 1) alluvial, deltaic and coastal depositional systems across the southern Po Plain, down to 150 m depth, provides an unambiguous documentation on the deformation of previously flat‐lying strata that goes back in time beyond the limits of morphological, historical and palaeoseismic records. Five prominent key horizons, accurately selected on the basis of their sedimentological characteristics and typified for their fossil content, were used as highly effective stratigraphic markers (M1 to M5) that can be tracked for tens of kilometres across the basin. A facies‐controlled approach tied to a robust chronology (102 radiocarbon dates) reveals considerable deformation of laterally extensive nearshore (M1), continental (M2 and M3) and lagoon (M4 and M5) marker beds originally deposited in a horizontal position (M1, M4 and M5). The areas where antiformal geometries are best observed are remarkably coincident with the axes of buried ramp anticlines, across which new seismic images reveal substantially warped stratal geometries of Lower Pleistocene strata. The striking spatial coincidence of fold crests with the epicentres of historic and instrumental seismicity suggests that deformation of marker beds M1 to M5 might reflect, in part at least, syntectonically generated relief and, thus, active tectonism. Precise identification and lateral tracing of chronologically constrained stratigraphic markers in the ¹⁴C time window through combined sedimentological and palaeoecological data may delineate late Quaternary subsurface stratigraphic architecture at an unprecedented level of detail, outlining cryptic stratal geometries at the sub‐seismic scale. This approach is highly reproducible in tectonically active Quaternary depositional systems and can help to assess patterns of active deformation in the subsurface of modern alluvial and coastal plains worldwide.     

Deposition and taphonomy of earthworm granules in relation to their interpretative potential in Quaternary stratigraphy

Calcium carbonate granules up to 2.5 mm in size are commonly found in Quaternary soils and sediments but have only rarely been used for any form of interpretation. Growing interest in recent years has focused on the concentration patterns in stratigraphy containing buried land surfaces, and the possibility of dating the granules. Making sense of either of these approaches requires a basic understanding of granule types, together with their modes of accumulation and destruction in stratigraphy. Details of the formation, morphology, deposition and post‐depositional changes are discussed along with the necessary ecological and pedological information on earthworm behaviour and effects, then summarised into a framework for interpretations. Copyright © 2006 John Wiley & Sons, Ltd.     

Late Quaternary erosion events in lowland and mid-altitude Tasmania in relation to climate change and first human arrival

The establishment of a chronology of landscape-forming events in lowland and mid-altitude Tasmania, essential for assessing the relative importance of climatic and human influences on erosion, and for assessing present erosion risk, has been limited by the small number of ages obtained and limitations of dating methods. In this paper we critically assess previous Tasmanian studies, list published radiocarbon ages considered to be dependable, present new radiocarbon and thermoluminescence (TL) ages for 25 sites around Tasmania, and consider the evidence for the hypotheses that erosion processes at low and mid altitudes have been: (1) purely climatically controlled; and (2) influenced both by climatic and anthropogenic (increased fire frequency) effects. A total of 94 dependable finite ages (calibrated for radiocarbon and ‘as measured’ for TL and optically stimulated luminescence (OSL) determinations) are listed for deposits comprising dunes, colluvium, alluvium and loess-like aeolian deposits. Two fall in the >100 ka period, 15 fall in the period 65–35 ka, and 77 fall in the period 35–0.3 ka. There was a sustained increase in erosion recorded in the period 35–15 ka, as reflected by a greater number of dated aeolian deposits during this period.We considered three possible biases that may have affected the age distribution obtained: the limitations of radiocarbon dating, sampling bias, and preservation bias. Sampling bias may have favoured more recent dune strata, but radiocarbon dating and preservation biases are unlikely to have significantly distorted the age distribution obtained.Long but intermittent aeolian deposition is recorded at two sites (Southwood B; c. 59–28 ka and Dunlin Dune; c. 29–14 ka) but there is no evidence of regional loess deposits such as found in New Zealand. The timing of increased erosion in Tasmania between 35 and 30 ka approximately coincides with the intermittent ten-fold increase of dust accumulation between 33 and 30 ka in the Antarctic Dome C ice core. The absence of widespread erosion before 35 ka, the abrupt increase of erosion around this time, the frequent association of erosion products with charcoal, the arrival of people in Tasmania at c. 40 cal ka, and the known use of fires by Aborigines to maintain areas of non-climax vegetation suggest that ecosystem disturbance by anthropogenic fires, in a drier climate than that presently prevailing, may have contributed to erosion in lowland and mid-altitude Tasmania after 35 ka. Thus the Tasmanian erosion record provides circumstantial support for the proposition that human dispersal in southeast Australia was accompanied by significant ecological change.     

Mønsted and Sevel salt domes,North Jutland,and their influence on the Quaternary morphology

This paper deals with two salt domes, Mønsted and Sevel, located in northern Jutland, and is primarily concerned with the problem of Quaternary salt tectonics and its possible relationship to the Quaternary morphology.Geological mapping of the two areas during the summers of 1965 and 1966 included a detailed surveying by means of a theodolite of a stream valley extending over the north-eastern part of Mønsted salt dome and of two valleys in the southern part of Sevel salt dome. In the Mønsted area extensive use of aerial photographs was made.In the light of the results of the geological study, an interpretation of the available geophysical data — in the case of Mønsted both gravimetric and magnetic — is attempted.

---

Zusammenfassung Die Salzstöcke Mønsted und Sevel in Nordjütland werden untersucht. Es wird versucht in beiden Gebieten eine Beziehung zwischen Quartär-Morphologie und Salztektonik herzustellen.Eine geologische Kartierung der beiden Gebiete wurde im Sommer 1965 und 1966 durchgeführt. Sie umfaßt eine detaillierte Vermessung des Bachlaufes, der über den Nordostteil des Mønsted-Salzstockes fließt, so wie zweier Täler im Südteil des Sevel-Salzstockes.Die Ergebnisse der geologischen Untersuchung werden in Beziehung zu den geophysikalischen Daten — für Mønsted gravimetrische und magnetische gesetzt.

---

Résumé Cet article traite deux dômes de sel, Mønsted et Sevel, situés au Nord du Jutland, et il s'occupe en premier lieu du problème de la tectonique du sel pendant le Quaternaire, et son éventuelle influence sur la morphologie quaternaire.L'étude géologique des deux régions, faite au cours des étés 1965 et 1966, comprenait un mesurage détaillé à l'aide d'un théodolite d'une vallée qui s étend sur la partie Nord-Est du dôme de sel à Mønsted et de deux vallées dans la partie Sud du dôme de sel à Sevel. Dans le cas de Mønsted on a fait ample usage de photographies aériennes.S'appuyant sur les résultats de l'étude géologique, l'auteur propose une interprétation des données géophysiques disponibles, qui dans le cas de Mønsted, comportent des mesurages tant gravimétriques que magnétiques.

---

Mø nsted Sevel . . ( Mønsted).

     

Quaternary sediments in the northwestern part of the Barents Sea and their relation to the underlying Mesozoic bedrock

A sedimentological study of Quaternary sediments from the northwestern part of the Barents Sea shows that their composition is controlled by the underlying Mesozoic bedrock and that very little sediment has been supplied from outside sources. The Quaternary sediments consist of Pleistocene glacial clays (moraines) and Holocene gravel, sand and mud, derived by erosion of the clay-rich moraines, which again have been derived from underlying Mesozoic rocks. On the shallow Spitsbergen Bank (30-100 m depth) we find a high energy facies of bioclastic carbonate sand and gravel and lag deposits of Mesozoic rock fragments from the underlying moraine. ¹⁴C-datings of the bioclastic carbonates (Molluscs and Barnacles) suggest that soft bottom conditions with Mya truncata prevailed in early Holocene time, succeeded by a hard bottom high energy environment with Barnacles in the last 2000-3000 years. This may be due to a southward movement of the oceanic polar front into the Spitsbergen Bank due to colder climate in Late Holocene (subatlantic) time, which at present day produces strong bottom currents down to 100 m depth. On the Spitsbergen Bank carbonate sedimentation has succeeded glacial sedimentation as a result of withdrawal of clastic sediment supply in Holocene time and high organic productivity because of upwelling. A similar mechanism may have been operating during earlier glaciations, i.e. in Late Precambrian time to produce an association of glacial and carbonate sediments although the biological precipitation was different at that time. In Late Precambrian time precipitation or carbonate by algaes may have occurred in colder water on the shelves due to higher saturation of carbonate in the sea water.     

Thickness of Quaternary deposits and their relation to the pre-Quaternary in the Fennoscandian border zone in Kattegat and Vendsyssel

Refraction seismic measurements from Kattegat have been analysed for information about Quaternary deposits. Preliminary results show a gradual increase in thickness of the Quaternary deposits from about 50m in the SW to 150–250m in the NE, close to the Swedish coast. A number of narrow zones with extraordinarily great thickness are superimposed on this surface. Comparisons with structural features in the pre-Quaternary, as known from reflection seismic investigations, strongly indicate that the 'Kattegat Basin' is a structural phenomenon generated by subsidence under tensional stress perpendicular to the Fennoscandian border zone. Stratigraphical analysis which is available from wells on the islands in Kattegat and in Vendsyssel shows that subsidence of the 'Kattegat Basin' was initiated in Holstein or earlier.     

Compositional variations in calciturbidites due to sea-level fluctuations,late Quaternary,Bahamas

Piston cores in Tongue of the Ocean, Bahamas, revealed an alternating sequence of periplatform ooze and bankderived turbidites of the past 5 glacial and interglacial periods. By using the point-count method we have analyzed the composition of the turbidite sediment. Variations in the bank-derived fraction are clearly linked to the glacial-interglacial cycles. Nonskeletal components (pellets; ooids; grapestones) are most abundant in interglacial turbidites, while skeletal components (calcareous algae; peneroplids and reef builders) dominate in glacial turbidites. We attribute this pattern to the exposure and flooding of the surrounding carbonate platforms during Late Quaternary sea-level cycles. Because nonskeletal sediment is produced in the interior of the platforms, its growth and subsequent export to the flanks are at a maximum when the banks are flooded, i.e. during interglacial periods. During glacials, skeletal grains dominate because the banks are exposed and carbonate production is limited to a narrow belt of skeletal sands and fringing reefs. The resulting compositional signal appeared to have a good correlation with aragonite variations in the periplatform ooze between the turbidites. Further, compositional variation parallels the change in turbidite frequency described earlier (»highstand bundling«). Frequency and composition of turbidites are both unaffected by diagenesis and therefore provide an excellent monitor of sealevel fluctuations.

---

Zusammenfassung In Kolbenlotkernen aus der Tongue of the Ocean, Bahamas, bestehen die jüngsten fünf Glaziale und Interglaziale aus einer Wechselfolge von Periplattform-Schlamm und Turbiditen mit Flachwasser-Material. Die Zusammensetzung der neritischen Kornfraktion in den Turbiditen wurde durch Punktzählung ermittelt. Sie schwankt deutlich im Verlauf eines glazialen Zyklus. Abiogene Komponenten (Pellets, Ooide, Traubenklumpen) dominieren in den interglazialen Turbiditen, während Biogene (Kalkalgen, peneroplide Foraminiferen und Riffbildner) in glazialen Turbiditen vorherrschen. Wir erklären diese Schwankungen mit dem Auftauchen und Überfluten der Bahama Bänke während der jungquartären Schwankungen des Meeresspiegels. Die abiogenen Komponenten werden auf der Innenseite der Plattformen gebildet. Ihre Produktion und Export zu den Plattformflanken erreichen daher ein Maximum während der interglazialen Hochstände des Meeres. In den Glazialen dominieren biogene Komponenten, weil die Plattformen trocken liegen und die Karbonat-Produktion auf einen schmalen Streifen von Saumriffen und Biogensanden beschränkt ist.Die Zusammensetzung der Turbidite variiert im gleichen Rhythmus wie der Aragonitgehalt der zwischengeschalteten Periplattform-Schlamme. Überdies korreliert die Zusammensetzung gut mit der Häufigkeitsverteilung der Turbidite. Während der Interglaziale sind Turbidite häufiger als während der Glaziale (»Hochstand-Bündel«). Häufigkeitsverteilung und Zusammensetzung der Turbidite zusammen ergeben ein gutes, durch Diagenese nicht verwischbares Abbild der Schwankungen des Meeresspiegels.

---

Résumé Dans le »Tongue of the Ocean« (Bahamas), des sondages à piston effectués dans les sédiments des cinq dernières périodes glaciaires et interglaciaires montrent une alternance de turbidites et de boues déposées en périphérie de plate-forme. La composition de la fraction néritique des turbidites, dé terminée par la méthode du compteur de points, montre une relation claire avec les cycles glaciaires. Les composants abiogènes (pellets, ooïdes, grapestones) dominent dans les turbidites interglaciaires, tandis que les composants biogènes (algues calcaires, foraminifères de type pénéroplide et organismes constructeurs) sont prépondérants dans les turbidites glaciaires. Nous attribuons cette répartition aux émersions et submersions successives du banc des Bahamas, consécutives aux variations du niveau de la mer au Quaternaire récent. Comme les composants abiogènes ont été formés sur la partie interne de la plate-forme, leur développement et leur transport vers les flancs étaient maximaux lorsque le banc était submergé, au cours des périodes interglaci aires. Par contre, les composants biogènes dominaient pendant les épisodes glaciaires, où la plate-forme était exondée et où la production de carbonate était restreinte à une zone étroite de récifs frangeants et de sables biogènes. Ces variations dans la composition des turbidites présentent une bonne corrélation avec la teneur en anhydrite des boues de périphérie de plate-forme intercalées entre les turbidites. Il existe également une bonne corrélation avec la fréquence des turbidites, plus élevée pendant les interglaciaires. La fréquence et la composition des turbidites ne sont pas affectées par la diagenèse et constituent donc un excellent témoin des fluctuations du niveau de la mer.

---

, «» , , . . . / , , / , , .. , . - . . . , . , . , . , / «Hochstand-Bndel» /. , .

     

柴西第四纪湖泊冰水沉积的发现及意义

柴达木盆地西部的茫崖坳陷发育了第四纪湖泊冰水沉积,其特征是灰绿、黄褐色页岩和泥岩中含大量的冰水滴石。滴石最大粒径可达4cm×12cm,成分复杂,有火山岩、变质岩及沉积岩。孢粉分析表明,其形成时代为第四纪,极有可能为更新世,与我国西部的第四纪冰期形成时代相同,但具体期次尚不能确定。柴西茫崖坳陷第四纪冰水沉积证据充分,对于研究我国第四纪冰期及青藏高原的形成演化、古气候、古地理具有重要意义。另外,第四纪冰水沉积充分说明在第四纪冰期青藏高原没有被整个大冰盖所覆盖。     

穆尼盆地第四纪深水弯曲水道:沉积构型、成因及沉积过程

深水水道是陆坡沉积的重要组成单元,深水水道储层受到广泛关注。基于高分辨率三维地震资料,利用地震属性、分频技术等研究穆尼盆地第四纪深水弯曲水道的沉积构型、成因及沉积过程,主要取得以下3个方面的成果:(1)建立了深水弯曲水道沉积构型模式。弯曲深水水道由水道和堤岸组成。堤岸脊将堤岸分成内堤岸和外堤岸两部分。水道由底部粗粒滞留沉积、深海泥质披覆沉积以及滑块组成。(2)深水水道早期为低弯曲水道,后期逐渐演化为高弯曲水道。(3)建立了深水弯曲水道沉积的岩相模式,深水弯曲水道由垂向加积水道和侧向迁移水道组成。顺重力流方向,侧向迁移带,内弯带以沉积作用为主,外弯带以侵蚀作用为主。垂向加积带,水道底部粗粒滞留沉积往往表现为垂向加积特征。深水弯曲水道岩相模式的建立对深水浊积水道储层准确预测具有重要的理论指导意义。     

Late Quaternary marine terraces in the Mediterranean coastal area of Syria: Geochronology and neotectonics

In order to provide new data on the neotectonics and geodynamic properties of western Syria, studies of marine terraces have been carried out. The most attention was paid to the lower terraces in the range of 3–5 to 30–35 m above sea level, because they have more complete distributions along the shore. The lower terraces were examined along the coastal area from Tartus to Latakia, and along the carbonate cliff on Arwad Island. Seven ²³⁰Th/U dates for these terraces are in the range of 85–130 ka, suggesting the age interval of the last interglacial (MIS 5). New dates on the lower terraces provide a basis for stratigraphical and geomorphological interpretation as well as neotectonic reconstruction. According to the geomorphological data and lithological composition of those terraces, two main uplifted blocks can be established. One coincides with the Latakia block, and another corresponds to the western margin of the Banias volcanic plateau. These blocks are divided by a subsided structure corresponding to the Nahr el Kebir graben. The amplitude of neotectonic uplifting in the Latakia and Banias blocks reaches 15–20 m for the Late Pleistocene.