Rip currents as a geological tool

This paper considers the nature and sedimentary significance of rip currents. Rip currents are the main factor responsible for the transport of coarse sediments from the littoral zone to greater depths. Such sediments, deposited outside the zone of wave deformation, may be identified as storm rip current increments within sediments deposited during fair weather. Composite beds deposited during a given wave cycle by storm rip currents are closely similar to ‘turbidites’ and many so called ‘fluxo-turbidites’ described from flysch deposits. Using data gathered in studies conducted on the modern Baltic coast, supplemented by experimental work and theoretical considerations, a sedimentary model is proposed. The model may be used to interpret possible rip current deposits among shallow water ‘turbidites’, and both modern storm sediments and ancient ‘tempestites’.     

Crustacean species new to Spitsbergen with notes on the polymorphism and the subfossil preservation of Cytherissa lacustris (G. O. Sars)

The copepods Limnocalanus macrurus G. O. Sars and Eucyclops serrulatus (Fisch.) and the ostracode Cytherissa lacustris (G. O. Sars), hitherto unknown on Spitsbergen, were found in Lake Rewatnet, the last species also in Lake Svartvatnet. Samples from parthenogenetic populations of C. lacustris showed a complete lack of electrophoretically detectable variability at four enzyme-encoding loci, two of which are highly variable in mainland populations. However, morphological variation in the carapace length and nodation was no less than in the mainland populations. The carapace valves of C. lacustris do not preserve well in the sediments of Rewatnet.     

Late Saalian climate changes in Europe in the light of pollen analysis and the problem of two-step deglaciation at the oxygen isotope stage 6/5e transition

Taking a palynological study from Dziewule in eastern Poland as an example, we discuss the problem of distinguishing the so-called 'Zeifen-Kattegat oscillation' in some European pollen profiles. In the light of pollen analysis, this is questionable, and therefore requires careful consideration. In Poland, the palynological succession from this period indicates a gradual evolution from open plant communities to a closed forest in which no record of a 'Younger Dryas' type cool event exists.     

Geochemical evolution of the Dras–Kohistan Arc during collision with Eurasia: Evidence from the Ladakh Himalaya, India

Abstract   The Dras 1 Volcanic Formation of the Ladakh Himalaya, India, represents the eastern, upper crustal equivalent of the lower crustal gabbros and mantle peridotites of the Kohistan Arc exposed in Pakistan. Together these form a Cretaceous intraoceanic arc now located within the Indus Suture zone between India and Eurasia. During the Late Cretaceous, the Dras–Kohistan Arc, which was located above a north-dipping subduction zone, collided with the south-facing active margin of Eurasia, resulting in a switch from oceanic to continental arc volcanism. In the present study we analyzed samples from the pre-collisional Dras 1 Volcanic Formation and the postcollisional Kardung Volcanic Formation for a suite of trace elements and Nd isotopes. The Kardung Volcanic Formation shows more pronounced light rare earth element enrichment, higher Th/La and lower ɛ_Nd values compared with the Dras 1 Volcanic Formation. These differences are consistent with an increase in the reworking of the continental crust by sediment subduction through the arc after collision. As little as 20% of the Nd in the Dras 1 Volcanic Formation might be provided by sources such as the Karakoram, while approximately 45% of the Nd in the Kardung Volcanic Formation is from this source. However, even before collision, the Dras–Kohistan Arc shows geochemical evidence for more continental sediment contamination than is seen in modern western Pacific arcs, implying its relative proximity to the Eurasian landmass. Comparison of the lava chemistry in the Dras–Kohistan Arc with that in the forearc turbidites suggests that these sediments are partially postcollisional, Jurutze Formation and not all pre-collisional Nindam Formation. Thus, the Dras–Eurasia collision can be dated as Turonian–Santonian (83.5–93.5 Ma), older than it was previously considered to be, but consistent with radiometric ages from Kohistan.     

Influence of climate on the variability of snails of the genus Viviparus in deposits of the Holsteinian (Mazovian) Interglacial from Ortel Krolewski, eastern Poland

Sediments of palaeolakes located in eastern Poland represent the Holsteinian (Mazovian) Interglacial, which corresponds to the Marine Isotope Stage 11 (MIS 11). Some of these sediments are characterized by an extremely rich occurrence of mollusc shells. A total of 1795 specimens of the snail Viviparus diluvianus were measured from 5 samples collected from a succession of lake deposits at Ortel Krolewski. The sample from the lowermost part of the succession (2.5 m) represents the Picea-Alnus pollen zone of the Holsteinian Interglacial. Samples from 2.0, 1.5, 1.0m are related to the Taxus Zone. Samples collected from the uppermost part of the succession (0.5 m) correspond to the Pinus Zone representing the so-called intra-interglacial cooling. The population of V. diluvianus displays variability correlated with climatic changes. The population from the Taxus Zone is characterized by a higher content of mature forms compared to the earlier population from the Picea-Alnus Zone. Because the mature individuals are slimmer than the juvenile forms, their last whorl is relatively lower and the aperture relatively smaller. In populations from the Taxus Zone the mean slimness of the shell therefore increases, followed by a decrease in the mean relative height of the last whorl and the mean relative aperture height.     

The magnetic susceptibility record in the Polish and western Ukrainian loess-palaeosol sequences conditioned by palaeoclimate

The magnetic susceptibility of loess-palaeosol sequences in southern Poland and western Ukraine varies mainly with the degree of decomposition of detrital magnetite grains conditioned by palaeoclimate. Relatively high susceptibility values were observed in the unweathered loess horizons and in accumulation horizons of the non-gleyed soils which contain relatively high amounts of paramagnetic fraction and pedogenic (?) magnetite. The susceptibility curves characteristic for Polish and western Ukrainian loess-palaeosol sequences may be directly correlated with oxygen-isotope fluctuations in deep-sea sediments. This correlation is more complex than that for the Chinese or Alaskan loess-palaeosol sequences. The major causes of the complexities are the relatively small thicknesses of the investigated sections (especially their older horizons) and the heterogeneity of geochemical processes that affected loess surface in the interglacial and interstadial times.     

Deep‐seated relict permafrost in northeastern Poland

Szewczyk, J. & Nawrocki, J. 2011: Deep‐seated relict permafrost in northeastern Poland. Boreas, Vol. 40, pp. 385–388. 10.1111/j.1502‐3885.2011.00218.x. ISSN 0300‐9483. A research borehole drilled in northeastern Poland revealed a permafrost layer at least 93 m thick within the Cretaceous sedimentary succession below a depth of 357 m. Its entire thickness has not been determined, owing to the borehole depth limit (450 m). The relict of permafrost, unexpected in this part of Europe, is in the ice–water transition phase at a temperature close to 0 °C. We estimate that the permafrost has been preserved in an area of several square kilometres located above the central part of the Suwa?ki anorthosite intrusion, which is covered by ～800 m of sedimentary rocks. We show that the remnants of the Last Glaciation, which ended at c. 13.4 ka BP, can, even at present, affect the thermal regime of the outer zone of the Earth's crust. These findings are of significant importance for the reconstruction of past climate conditions.     

Climate stability during the Eemian – new pollen evidence from the Nidzica site,northern Poland

Bińka, K., Nitychoruk, J. & Dzier?ek, J. 2010: Climate stability during the Eemian – new pollen evidence from the Nidzica site, northern Poland. Boreas, 10.1111/j.1502‐3885.2010.00179.x. ISSN 0300‐9483 Interglacial sediments at Nidzica, northern Poland were investigated by means of pollen and isotope analysis. These deposits accumulated in an extensive basin through most of the Eemian and Early Weichselian, practically without stratigraphic gaps. Continuous subsidence of the basin floor has resulted in the accumulation of a great thickness of lacustrine sediments, consisting mostly of calcareous gyttja. The course of pollen and isotope curves in the interglacial interval does not indicate the abrupt climatic shifts reported from some other continental climatic archives. Particularly important has been the reconstruction of the final stages of the Eemian, a potential analogue for future climatic change in the late Holocene. At Nidzica, this period is registered as a gradual modification of forest composition, devoid of any pulsations in which temperate forest is followed by terminal, boreal pine–birch communities.     

Geological-geomorphological analysis and 14C dating of submoraine organogenic deposits within the Renardbreen outer margin, Wedel Jarlsberg Land, Spitsbergen

Amazing organogenic deposits were encountered within the terminal moraine zone of Renardbreen, north-western part of Wedel Jarlsberg Land. Pollen analyses and ^,14C dating locate the deposits at the Middle Late Subatlantic transition. The position of these deposits indicates possible glacial advances 3,500-2,000 years BP and during the Little Ice Age, respectively. Remnants of human activity at least as old as the 9th century were also found within organogenic deposits.     

Lodgement till deposition and deformation investigated by macroscopic observation, thin-section analysis and electron microscope study at site Dçbe, central Poland

Macroscopic observation, thin-section analysis and electron microscope study were used in a detailed examination of till exposed in a valley escarpment. The till displays two kinds of bedding: (1) beds of different colour (lithology) that are not separated from one another by distinct boundaries, and (2) beds that are separated by distinct subhorizontal planes of discontinuity, commonly consisting of several beds of the first type. Beds showing no clear separation are interpreted as having been deposited through continuous lodgement, while the distinct discontinuities most probably record sliding planes of the glacier sole during breaks in till deposition. These features, along with the qualitative and quantitative microscopic evidence, indicate that the lower and middle parts of the till were deposited by hard lodgement. The process of deposition was interrupted several times by episodes of non-deposition, some of them accompanied by glacial erosion. The upper part of the till was deposited by continuous lodgement that was transitional between hard and soft lodgement processes. Such a succession indicates the prevalence of a cooler subglacial thermal regime which changed upwards into a milder one. The till examined displays mainly brittle deformation - namely Riedel shears that are primarily concentrated between the subhorizontal discontinuities characteristic of the lower and middle parts of the section. A dense set of Riedel shears also cuts thicker portions of the upper part of the till and, in some places, such shears combine along additional subhorizontal (discrete) shear planes. The direction of the fractures, as well as the strong fabric orientation of stone a-axes within the till, indicate an ice flow in the studied area from NW to SE.