Hasil untuk "Stratigraphy"

Brian Taylor

Recently published marine geophysical and seafloor drilling data permit a substantive reappraisal of the rifting and spreading that formed the South China Sea (SCS). The SCS rifted margins are different from those of the Atlantic type, having higher strain rates, younger orogenic crust, and distributed syn-rift magmatism. Rifting ~66–11 Ma and spreading 30–14 Ma split a Cretaceous Andean arc and forearc, producing >700 km of seafloor spreading in the east and a ~2000-km-wide rifted margin in the west. Luconia Shoals–Dangerous Grounds–Reed Bank–north Palawan–SW Mindoro were separated from China when the SCS opened. Brittle faulting of the upper crust was decoupled from ductile flow and magmatic intrusion of the lower crust, producing wide rifting with thin spots held together by less extended surrounds. Sediments accumulated in inter-montane lakes. Transform faults formed at/after breakup to link offset spreading segments. Spreading in the eastern subbasin from C11n to C5AD was at rates averaging 62 mm/yr, 30–24 Ma, decreasing to 38.5 mm/yr younger than 23 Ma. Spreading reorganization was common as margin segments broke up to the SW and spreading directions changed from ~N-S before 23 Ma to NW-SE after 17 Ma.

Christos Tsakalidis, George E. Konidaris, Evangelia Tsoukala et al.

Dental wear analyses of extinct animals offer key insights into their dietary preferences and in turn contribute substantially to palaeoenvironmental reconstructions, leading to more accurate interpretations about past ecosystems. This study employs dental mesowear analysis on Pliocene and Pleistocene elephants and mammoths from several localities in Northern Greece (Ptolemais Basin, Mygdonia Basin, Drama Basin, and the Neapolis-Grevena Basin), aiming to classify them into three main dietary categories (browsers, mixed-feeders, grazers) and investigate potential niche partitioning. The method relies on documenting the wear pattern of molar surfaces through angle measurements on the enamel ridges, which reflect the average annual diet of the examined taxon and in turn the annual ecological conditions of the studied area. Prior to the palaeodietary study and in order to ensure the taxonomic attribution of the examined specimens, a taxonomic review was conducted which confirmed the presence of the mammoths <i>Mammuthus rumanus</i>, <i>Mammuthus meridionalis</i> (southern mammoth), and <i>Mammuthus trogontherii</i> (steppe mammoth), and the European straight-tusked elephant <i>Palaeoloxodon antiquus</i>. Dental mesowear results indicate a grazing diet for <i>M.</i> (cf.) <i>rumanus</i>, a mainly browsing diet for <i>M. meridionalis</i> but mixed-feeding to grazing for the subspecies <i>Mammuthus meridionalis vestinus</i>, a grazing one for <i>M. trogontherii</i>, and a wide diet spectrum for <i>P. antiquus</i>, including browsing, mixed-feeding and grazing, depending on the locality. This study expands our knowledge on the palaeoecology of Greek proboscideans and further highlights the importance of mesowear analysis on proboscidean teeth for palaeodietary and palaeoenviromental inferences.

Anna Maria Mercuri, Assunta Florenzano, Eleonora Clò et al.

Palynology deals with several topics closely linked to sustainability [...]

Kun-sheng Du, Jin Guo, Sarah R Losso et al.

Euarthropods are an extremely diverse phylum in the modern, and have been since their origination in the early Palaeozoic. They grow through moulting the exoskeleton (ecdysis) facilitated by breaking along lines of weakness (sutures). Artiopodans, a group that includes trilobites and their non-biomineralizing relatives, dominated arthropod diversity in benthic communities during the Palaeozoic. Most trilobites – a hyperdiverse group of tens of thousands of species - moult by breaking the exoskeleton along cephalic sutures, a strategy that has contributed to their high diversity during the Palaeozoic. However, the recent description of similar sutures in early diverging non-trilobite artiopodans means that it is unclear whether these sutures evolved deep within Artiopoda, or convergently appeared multiple times within the group. Here, we describe new well-preserved material of Acanthomeridion, a putative early diverging artiopodan, including hitherto unknown details of its ventral anatomy and appendages revealed through CT scanning, highlighting additional possible homologous features between the ventral plates of this taxon and trilobite free cheeks. We used three coding strategies treating ventral plates as homologous to trilobite-free cheeks, to trilobite cephalic doublure, or independently derived. If ventral plates are considered homologous to free cheeks, Acanthomeridion is recovered sister to trilobites, however, dorsal ecdysial sutures are still recovered at many places within Artiopoda. If ventral plates are considered homologous to doublure or non-homologous, then Acanthomeridion is not recovered as sister to trilobites, and thus the ventral plates represent a distinct feature to trilobite doublure/free cheeks.

Elena V. Petrova, Artyom V. Gusarov, Achim A. Beylich

Buried river valleys from the Neogene–Quaternary time are widespread throughout the Middle Volga region of the Russian Plain. They have been studied for a long period, since the 1940s, with the last major generalizations dating back to the 1980s. This paper presents new results based on GIS mapping using materials from the state geological study of the region in 1960–1970, 1984–1996 and 2000–2002. On the whole, the pattern of the buried valley network is close to the modern valley network of the region. During the Quaternary, the right-sided displacement of the valley incisions prevailed. The incisions of modern river valleys are located above the Neogene (pre-Akchagyl) incisions almost throughout the entire territory. The vertical displacement amplitude ranges from 30 to 200 m. The morphometric characteristics of the paleovalleys (the depth and width of the incisions, as well as the gradients of the bottoms of the paleovalleys) exceeded modern ones. The maximum values were typical for the middle Paleo-Volga valley: the width of the valley reached 10 km, the incision depth was−201.4 m below sea level and the bottom gradient was 0.9–5.0 m/km. The most important factor that influenced the position of paleovalleys and their morphological appearance was fluctuations in the level of the Caspian paleowaterbody. According to this study, the development of paleovalleys began in the Miocene and ended in the Early Quaternary. The alluvial–lacustrine type of sedimentation was predominant. The results of this work contribute to the study of the paleogeography of the Cenozoic of the southeast of the Russian Plain.

Gerson Fauth, Henrique Parisi Kern, Jorge Villegas-Martín et al.

Abstract This study reports a set of primeval marine incursions identified in two drill cores, 1PS-06-CE, and 1PS-10-CE, which recovered the Barbalha Formation, Araripe Basin, Brazil. Based on a multi-proxy approach involving stratigraphy, microbiofacies, ichnofossils, and microfossils, three short-lived marine incursions were identified, designated Araripe Marine Incursions (AMI) 1–3. AMI-1 and AMI-2, which occur within the shales of the Batateira Beds (lower part of the Barbalha Formation), were identified by the occurrence of benthonic foraminifera, calcareous nannofossils, dinocysts, and a mass mortality event of non-marine ostracods. AMI-3 was recognized in the upper part of the Barbalha Formation, based on the occurrence of ichnofossils and planktonic foraminifera. The observation of the planktonic foraminifera genus Leupoldina for the first time in the basin indicates early Aptian/early late Aptian age for these deposits, and the first opportunity of correlation with global foraminifera biozonation. Our findings have implications for the breakup of the Gondwana Supercontinent, as these incursions represent the earliest marine-derived flooding events in the inland basins of northeastern Brazil.

Erik Tihelka, Chenyang Cai

Yan Zheng, Haiyan Hu, Dong Chen et al.

The present corrigendum corrects errors that occurred in: Zheng Y., Hu H., Chen D., Chen J., Zhang H. & Rasnitsyn A.P. 2021. New fossil records of Xyelidae (Hymenoptera) from the Middle Jurassic of Inner Mongolia, China.  European Journal of Taxonomy 733: 146–159. https://doi.org/10.5852/ejt.2021.733.1229

John Parianos, Anthony O’Sullivan, Pedro Madureira

The Clarion Clipperton Zone (CCZ) hosts the most valuable deposit of polymetallic nodules yet discovered. International Seabed Authority exploration contractors, such as Tonga Offshore Mining Limited, Nauru Ocean Resources Incorporated and Marawa Research and Exploration Limited, routinely conduct ship-based 12 kHz multibeam echosounder surveys over all or parts of their exploration contract areas. This is often supported by physical seabed samples, side-scan sonar, sub-bottom profile sonar and seabed photographs. Geological maps for seven discrete mapped areas are presented. Basaltic abyssal plains of mid-Eocene to early Miocene age are overlain by 75–100 m of mid-Eocene and younger deep-sea chalks of the Marquesas Oceanic Formation. In turn, the chalk is overlain by up to 27 m of early Miocene to present, often mobile, siliceous clay-ooze sediment of the Clipperton Oceanic Formation. This stratigraphy is crosscut by a very wide variety of mostly volcanic magmatic rock units.

B. Guillaume, G. M. Gianni, G. M. Gianni et al.

<p>Geological settings characterized by multiple coeval tectonic regimes provide a unique opportunity to understand complex interactions among different geodynamic processes. However, they remain comparatively less studied from an experimental point of view than areas with more simple patterns of deformation resulting from primary plate–boundary interactions. Here, we carried out analog experiments involving simultaneous shortening and orthogonal extension under different rheological conditions, including the effect of crustal inheritance. We performed brittle experiments and brittle–ductile experiments to simulate cases of “strong” and “weak” crusts, respectively. We present two types of experiments: (i) one-stage experiments with either shortening only or synchronous orthogonal shortening and stretching and (ii) two-stage experiments with a first stage of stretching and a second stage with either shortening only or synchronous orthogonal shortening and stretching. In our models, deformation is accommodated by a combination of normal, thrust, and strike-slip faults with structure location depending on boundary conditions and crustal inheritance. For brittle models, we show that the three types of structures can develop at the same time for intermediate ratios of stretching (extension) over shortening rates (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">1.4</mn><mo>&lt;</mo><msub><mi>V</mi><mtext>e</mtext></msub><mo>/</mo><msub><mi>V</mi><mtext>s</mtext></msub><mo>&lt;</mo><mn mathvariant="normal">2</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="75pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="af69233c84ff4d4adccb736f107da1e9"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="se-13-1393-2022-ie00001.svg" width="75pt" height="14pt" src="se-13-1393-2022-ie00001.png"/></svg:svg></span></span>). For lower ratios, deformation is accommodated by in-sequence shortening-orthogonal thrust faults and stretching-orthogonal normal faults at the edges of the model (when <span class="inline-formula"><i>V</i>_e&gt;0</span>). For larger ratios and for the same amount of stretching, deformation is accommodated by normal faults at edges and in the center of the model as well as by conjugate strike-slip faults at the edges of the model. For brittle–ductile models, we always observe strike-slip faults that crosscut the entire model. They are associated with shortening-orthogonal thrust faults for models with low <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>V</mi><mtext>e</mtext></msub><mo>/</mo><msub><mi>V</mi><mtext>s</mtext></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="28pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="21734ff4312cbf6c18c8504a92708291"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="se-13-1393-2022-ie00002.svg" width="28pt" height="14pt" src="se-13-1393-2022-ie00002.png"/></svg:svg></span></span> and no initial extensional stage or stretching-orthogonal normal faults for models with high <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>V</mi><mtext>e</mtext></msub><mo>/</mo><msub><mi>V</mi><mtext>s</mtext></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="28pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="d9182a6738f95271133780575c99e077"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="se-13-1393-2022-ie00003.svg" width="28pt" height="14pt" src="se-13-1393-2022-ie00003.png"/></svg:svg></span></span> and an initial extensional stage. Whatever the crustal strength, the past deformation history, and the stretching / shortening ratio, both normal and thrust faults remain with similar orientations, i.e., stretching-orthogonal and shortening-orthogonal, respectively. Instead, strike-slip faults exhibit orientations with respect to the shortening direction that vary between <span class="inline-formula">∼0</span> and <span class="inline-formula">∼65</span><span class="inline-formula">^∘</span>. Strike-slip faults parallel to the shortening direction develop in previously extended portions of models with a brittle–ductile crust, while strike-slip faults with a high angle form at the boundaries of the brittle model, their orientation being to some extent influenced by pre-existing or newly forming graben in the center of the model. We also show that extensional structures formed during a first stage of deformation are never inverted under orthogonal shortening but can be reactivated as normal or strike-slip faults depending on <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>V</mi><mtext>e</mtext></msub><mo>/</mo><msub><mi>V</mi><mtext>s</mtext></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="28pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="7c61cb28ca59a97cd73b0a86a7a32130"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="se-13-1393-2022-ie00004.svg" width="28pt" height="14pt" src="se-13-1393-2022-ie00004.png"/></svg:svg></span></span>. Our experiments reproduce <span class="inline-formula"><i>V</i></span>-shaped conjugate strike-slip systems and normal faulting during compression similar to structures observed in the Tibetan Plateau, the eastern Alps, western Anatolia, and the Central Asia orogen. Models with two-stage deformation show variable extensional to strike-slip reactivation of former extensional basins during basin-parallel shortening, which resembles synorogenic foreland transtensional reactivations documented in the Baikal and Golfo de San Jorge basins.</p>

C. T. Bolton, E. Gray, E. Gray et al.

<p>In the modern northern Indian Ocean, biological productivity is intimately linked to near-surface oceanographic dynamics forced by the South Asian, or Indian, monsoon. In the late Pleistocene, this strong seasonal signal is transferred to the sedimentary record in the form of strong variance in the precession band (19–23 kyr), because precession dominates low-latitude insolation variations and drives seasonal contrast in oceanographic conditions. In addition, internal climate system feedbacks (e.g. ice-sheet albedo, carbon cycle, topography) play a key role in monsoon variability. Little is known about orbital-scale monsoon variability in the pre-Pleistocene, when atmospheric CO<span class="inline-formula">₂</span> levels and global temperatures were higher. In addition, many questions remain open regarding the timing of the initiation and intensification of the South Asian monsoon during the Miocene, an interval of significant global climate change that culminated in bipolar glaciation. Here, we present new high-resolution (<span class="inline-formula">&lt;1</span> kyr) records of export productivity and sediment accumulation from International Ocean Discovery Program Site U1443 in the southernmost part of the Bay of Bengal spanning the late Miocene (9 to 5 million years ago). Underpinned by a new orbitally tuned benthic isotope stratigraphy, we use X-ray fluorescence-derived biogenic barium variations to discern productivity trends and rhythms. Results show strong eccentricity-modulated precession-band productivity variations throughout the late Miocene, interpreted to reflect insolation forcing of summer monsoon wind strength in the equatorial Indian Ocean. On long timescales, our data support the interpretation that South Asian monsoon winds were already established by 9 Ma in the equatorial sector of the Indian Ocean, with no apparent intensification over the latest Miocene.</p>

Elena A. Hensel, Ralf Vogelsang, Tom Noack et al.

The preservation of archaeological remains and environmental information in a sediment accumulation can vary in caves and rockshelters, depending on external climatic conditions, and the circumstances within the shelter. Several sediment stratigraphies in the Horn of Africa are characterized by erosion layers, discordances and chronological gaps, that create uncertainties about the impact of climatic and environmental shifts on human settlements. Archaeological sites in Ethiopia that preserve information about human occupation during the Upper Pleistocene and Holocene often deal with major gaps during a period corresponding to MIS 2. In this study we present the first results of sedimentological, geochemical analyses and radiocarbon dating at Sodicho Rockshelter (1930 m above sea level) that provide evidence on high altitude settlement during this mentioned chronostratigraphic gap and subsequent time slices. This new archaeological site in the southwestern Ethiopian Highlands hosts a 2-m-long sediment record. So far, a stratigraphy has been excavated that dates back to ∼27 ka, including several settlement phases of Late Pleistocene and Holocene hunter-gatherers and providing information on environmental changes. A multiproxy approach was chosen to establish a first general stratigraphy of the site and to disentangle the sediment composition as well as site formation processes. The results suggest a variation of allochthonous and autochthonous geogenic deposits, and anthropogenic accumulation processes. With the help of radiocarbon dating, anthropogenic layers were dated covering the arid Last Glacial Maximum (LGM, ∼21 ± 2 ka). The occupation phases were interrupted in cause of environmental changes. The most prominent is the accumulation of reddish, archaeological sterile deposits that can be chronologically associated with the African Humid Period (AHP, ∼15–5 ka BP). Geochemical records point to dry spells within this humid phase, suggesting correlations with regional climate signals of lacustrine sediments. These sediment accumulations of past wet conditions are covered by alternating layers of Holocene volcanic fallout and sediments with preserved cultural material. Our study provides a preliminary impression of still poorly understood time periods of human occupation in the southwestern Ethiopian Highlands. The data obtained from Sodicho Rockshelter could validate the current state of knowledge and partially reduce the chronostratigraphic gap.

N. Ross, H. Corr, M. Siegert

<p>It has been hypothesized that complex englacial structures identified within the East Antarctic and Greenland ice sheets are generated by (i) water freezing to the ice sheet base and evolving under ice flow, (ii) deformation of ice of varying rheology, or (iii) entrainment of basal material. Using ice-penetrating radar, we identify a widespread complex of deep-ice facies in West Antarctica that exist in the absence of basal water. These deep-ice units are extensive, thick (<span class="inline-formula">&gt;500</span>&thinsp;m), and incorporate multiple highly reflective englacial layers. At the lateral margin of an enhanced flow tributary of the Institute Ice Stream, these units are heavily deformed and folded by the action of lateral flow convergence. Radar reflectivity analysis demonstrates that the uppermost reflector of the deep-ice package is highly anisotropic, due to abrupt alternations in crystal orientation fabric, and consequently will have a different rheology to the ice above and below it. Deformation and folding of the deep-ice package is an englacial response to the combination of laterally-convergent ice flow and the physical properties of the ice column.</p>

J. E. Pohlner, J. E. Pohlner, A. K. Schmitt et al.

<p>Baddeleyite (<span class="inline-formula">ZrO₂</span>) is widely used in U–Pb geochronology but analysis and age interpretation are often difficult, especially for samples which have experienced post-intrusive alteration and/or metamorphism. Here, we combine high spatial resolution (secondary ionization mass spectrometry, SIMS) and high-precision (isotope dilution thermal ionization mass spectrometry, ID-TIMS) analyses of baddeleyite from the Spread Eagle Intrusive Complex (SEIC) and Cape St. Mary's sills (CSMS) from Newfoundland. Literature data and our own detailed microtextural analysis suggest that at least seven different types of baddeleyite–zircon intergrowths can be distinguished in nature. These include secondary baddeleyite inclusions in altered zircon, previously unreported from low-grade rocks, and likely the first discovery of xenocrystic zircon inclusions mantled by baddeleyite. <span class="inline-formula">²⁰⁷Pb∕²⁰⁶Pb</span> baddeleyite dates from SIMS and ID-TIMS mostly overlap within uncertainties. However, some SIMS sessions of grain mounts show reverse discordance, suggesting that bias in the U&thinsp;<span class="inline-formula">∕</span>&thinsp;Pb relative sensitivity calibration affected <span class="inline-formula">²⁰⁶Pb∕²³⁸U</span> dates, possibly due to crystal orientation effects, and/or alteration of baddeleyite crystals, which is indicated by unusually high common-Pb contents. ID-TIMS data for SEIC and CSMS single baddeleyite crystals reveal normal discordance as linear arrays with decreasing <span class="inline-formula">²⁰⁶Pb∕²³⁸U</span> dates, indicating that their discordance is dominated by recent Pb loss due to fast pathway diffusion or volume diffusion. Hence, <span class="inline-formula">²⁰⁷Pb∕²⁰⁶Pb</span> dates are more reliable than <span class="inline-formula">²⁰⁶Pb∕²³⁸U</span> dates even for Phanerozoic baddeleyite. Negative lower intercepts of baddeleyite discordia trends for ID-TIMS dates for SEIC and CSMS and direct correlations between ID-TIMS <span class="inline-formula">²⁰⁷Pb∕²⁰⁶Pb</span> dates and the degree of discordance may indicate preferential <span class="inline-formula">²⁰⁶Pb</span> loss, possibly due to <span class="inline-formula">²²²Rn</span> mobilization. In such cases, the most reliable crystallization ages are concordia upper intercept dates or weighted means of the least discordant <span class="inline-formula">²⁰⁷Pb∕²⁰⁶Pb</span> dates.</p> <p>We regard the best estimates of the intrusion ages to be <span class="inline-formula">498.7±4.5</span>&thinsp;Ma (2<span class="inline-formula"><i>σ</i></span>; ID-TIMS upper intercept date for one SEIC dike) and <span class="inline-formula">439.4±0.8</span>&thinsp;Ma (ID-TIMS weighted mean <span class="inline-formula">²⁰⁷Pb∕²⁰⁶Pb</span> date for one sill of CSMS). This first radiometric age for the SEIC is consistent with stratigraphic constraints and indicates a magmatic episode prior to opening of the Rheic Ocean. Sample SL18 of the Freetown Layered Complex (FLC), Sierra Leone, was investigated as an additional reference. For SL18, we report a revised <span class="inline-formula">201.07±0.64</span>&thinsp;Ma intrusion age, based on a weighted mean <span class="inline-formula">²⁰⁷Pb∕²⁰⁶Pb</span> date of previous and new baddeleyite ID-TIMS data, agreeing well with corresponding SIMS data. Increasing discordance with decreasing crystal size in SL18 indicates that Pb loss affected baddeleyite rims more strongly than cores. Our SL18 results validate that the SIMS in situ<span id="page188"/> approach, previously used for Precambrian and Paleozoic samples, is also suitable for Mesozoic baddeleyite.</p>

César Jacques-Áyala

The Late Cretaceous El Chanate Group is a clastic and volcanic sequence, ranging from 700 to more tan 2,800 m in thickness, deposited in a continental basin. It disconformably overlies the Lower Cretaceous Bisbee Group and underlies the Late Cretaceous (71 Ma) Tarahumara Formation. On the basin of major upward-fining eyeles and different conglomerate composition, three stratigraphic units were identified in the Sierra El Chanate: the Pozo Duro (oldest), Anita, and Escalante (youngest) formations. El Chanate Group and its three formations are proposed herein as formal stratigraphic units… download the full paper in PDF.

S. H. R. Sadeghi, L. Gholami, M. Homaee et al.

Various organic and inorganic mulches are used for soil conservation purposes, the effectiveness of which on soil characteristics has not been comprehensively considered from different aspects. The present study surveys the efficiency of straw mulch, manure and TA-200 polyacrylamide with respective rates of 500, 300 and 50 g m^&minus;2 in changing sediment concentration and soil loss. The experiments were conducted for sandy-loam soil taken from a summer rangeland, the Alborz Mountains, northern Iran. The experiments were performed under laboratory conditions with simulated rainfall intensities of 30, 50, 70 and 90 mm h^&minus;1 and a slope of 30%. The results showed that the straw mulch decreased soil erosion at rate of 45.60% compared to the control plots and performed better than manure (8.98% reduction) and PAM (4.74% reduction). The results showed that the maximum reduction in sediment concentration and soil loss for all soil amendments occurred at the rainfall intensity of 90 mm h^&minus;1 with the rates of 58.69 and 63.24% for straw mulch, 14.65 and 13.14% for manure and 20.15 and 23.44% for TA-200.

D. B. Sobolev, A. V. Zhuravlev, V. V. Popov et al.

The Upper Visean-Serpukhovian deep-water shelf succession is described in the Subpolar Urals. Turbidite model of the sequence forming and direction of the carbonate material transport are proposed. The bioherm and shoal facial belt of the shelf margin is supposed as a main source of the material.

Ivanišević Vujadin, Bugarski Ivan

Roman Margum and Mediaeval town of Morava, situated on the Orašje site in Dubravica at the confluence of the Velika Morava and the Danube, could not have been analysed more thoroughly in the past because of the damage caused by the river bed displacements and soil erosion on the one hand, and dense vegetation growing on such a moist terrain on the other. Archaeological research has so far failed to produce even a site plan. Available data on this important site are contradictory to a considerable extent, so the information one could obtain from the written and cartographic sources needed to be confronted with the archaeological ones and, especially, those derived from the recent LiDAR scanning of the terrain, conducted within the scope of the Archaeo-Landscapes Europe Project. Among the most important plans of the confluence area are those left by Marsigli in the 18th and Kanitz in the 19th century. Felix Kanitz, the famous Balkan traveler, also provided us with a textual description of his visit to the site in 1887. Our analyses of the two plans have revealed a number of inaccuracies. Through analyses of the obtaineded LiDAR scans, however, the preserved area of the two settlements has been clearly demarcated, measuring 7-8 hectares, and the eastern edge of the Roman agglomeration - presumed already in the course of the 2011 excavations - was confirmed. Most probably it was the eastern rampart of the Roman fortification. Apart from this, the purpose of a canal stretching along the whole plateau, and mentioned by Kanitz, has been established. Given that to the east of the canal there was the presumably Roman rampart, and to the west of it there were recently excavated ruins of Roman buildings, the canal itself must have been of a more recent date. Bearing in mind the established vertical stratigraphy of the site, we conclude that it was in fact a Mediaeval defence trench. The topography of the nearby fort Kulič has been studied as well. It is often believed that this fortification was originally built in Roman times, but the analyses of DTM have shown the fort erected on an embankment, round in shape, i.e. on the more elevated terrain in comparsion to the largest part of the confluence area, where most of Roman Margum and Mediaeval Morava has been wiped out by water. So the Kulič fortification could have been originally erected only afterwords, i.e. in Turkish times. There are some data from the written sources to corroborate such a date, and we also know of two later accounts describing the 17th century settlement in front of it. There has been no field confirmation so far, but thanks to the results of LiDAR scanning one may observe the traces of a small settlement south of the fortification, protected by a trench. [Projekat Ministarstva nauke Republike Srbije, br. 177021: ArchaeoLandscapes Europe i Procesi urbanizacije i razvoja srednjovekovnog društva]

Janez Mulec, Svatava Kubešova

In subterranean environments phototrophic organisms can grow only in the proximity of light sources. In a study from eight Slovenian show caves: Črna jama, Kostanjeviška jama, Krška jama, Pekel pri Zalogu, Pivka jama, Postojnska jama, Škocjanske jame, Županova jama and two mines, Idrija mer­cury mine and Mežica lead and zinc mine, equipped for tourist visits, 37 taxa of Bryophyta and Pteridophyta were identified. The most frequent organisms were mosses Amblystegium ser­pens, Brachythecium sp., Eucladium verticillatum and Fissidens taxifolius. The highest diversity of bryophytes was recorded in Mežica mine with16 identified taxa where lamps are on con­tinuously. Bryophytes were collected at wide range of photo­synthetic photon flux densities (PPFD) from 0.2 to 530.0 μmol photons/m2/s. Eucladium verticillatum had the highest span of PPFDs, ranging from 1.4 to 530.0 μmol photons/m2/s. Bryo­phytes compensate for low PPFD withlonger exposure to light irradiance. Cratoneuron filicinum identified in Mežica mine de­veloped sporophytes at 2.1 and 2.4 μmol photons/m2/s, in Post­ojnska jama Brachythecium salebrosum developed sporophytes at 4.7 μmol photons/m2/s. Recolonization of lampenflora in show caves where bleachis applied to prevent its growthis still successful at sites that are exposed to long periods of irradiance and highPPFDs.

Andrej Kranjc