Energy Decay of the 2004 Sumatra Tsunami in the World Ocean

The catastrophic Indian Ocean tsunami generated off the coast of Sumatra on 26 December 2004 was recorded by a large number of tide gauges throughout the World Ocean. This study uses gauge records from 173 sites to examine the characteristics and energy decay of the tsunami waves from this event in the Indian, Atlantic and Pacific oceans. Findings reveal that the decay (e-folding) time of the tsunami wave energy within a given oceanic basin is not uniform, as previously reported, but depends on the absorption characteristics of the shelf adjacent to the coastal observation site and the time for the waves to reach the site from the source region. In general, the decay times for island and open-ocean bottom stations are found to be shorter than for coastal mainland stations. Decay times for the 2004 Sumatra tsunami ranged from about 13 h for islands in the Indian Ocean to 40–45 h for mainland stations in the North Pacific.     

Global Lightning Activity on the Basis of Inversions of Natural ELF Electromagnetic Data Observed at Multiple Stations around the World

The monitoring of global lightning activity and its spatial and temporal variations is known to be very essential for the study of global warming, the subject of greatest concern to human beings on planet Earth today. As a method of remote sensing for the global lightning distribution, we have proposed an inverse problem by using the data of natural electromagnetic noise in the ELF (extremely low frequency) Schumann resonance (SR) band observed simultaneously at a few stations around the world. The fundamentals of this inversion problem (or ELF tomography) to the SR data have been presented and the first attempt to deduce the global lightning distribution by means of the real SR data has been performed, which has indicated a possibility of snapshots of well-known thunderstorm centers on the globe. This ELF tomography consists of two stages. The first stage is the inversion of the ELF field power spectra to the distribution of lightning intensity by distance relative to an observation point. The obtained distance profiles of intensity of sources at a few stations are used as tomographic projections for reconstructing a spatial distribution of sources in the second stage. Maps of the global lightning distributions constructed by the result of inversions of ELF background field spectra obtained from three stations around the world show that the most active regions vary meridionally on the diurnal time scale being connected mainly with continental areas in the tropics. We do hope that this kind of inversion method to multi-stationed ELF data will be of great importance in the future.     

Detection of surface change in complex topography using terrestrial laser scanning: application to the Illgraben debris‐flow channel

Detection of surface change is a fundamental task in geomorphology. Terrestrial laser scanners are increasingly used for monitoring surface change resulting from a variety of geomorphic processes, as they allow the rapid generation of high‐resolution digital elevation models. Irrespective of instrument specifics, survey design or data processing, such data are subject to a finite level of ambiguity in position measurement, a consideration of which must be taken into account when deriving change. The propagation of errors is crucial in change detection because even very small uncertainties in elevation can produce large uncertainties in volume when extrapolated over an area of interest. In this study we propose a methodology to detect surface change and to quantify the resultant volumetric errors in areas of complex topography such as channels, where data from multiple scan stations must be combined. We find that a commonly proposed source of error – laser point elongation at low incidence angles – has a negligible effect on the quality of the final registered point cloud. Instead, ambiguities in elevation inherent to registered datasets have a strong effect on our ability to detect and measure surface change. Similarly, we find that changes in surface roughness between surveys also reduce our ability to detect change. Explicit consideration of these ambiguities, when propagated through to volume calculations, allows us to detect volume change of 87 ± 5 m³, over an area of ～ ?4900 m², due to passage of a debris flow down a 300 m reach of the Illgraben channel in Switzerland. Copyright © 2011 John Wiley & Sons, Ltd.     

Calcium isotopes in fossil bones and teeth — Diagenetic versus biogenic origin

We present the first systematic study of Ca isotopes (δ^44/40Ca) in Late Triassic to Late Cretaceous dinosaur bones and teeth (enamel and dentin) from sympatric herbivorous and carnivorous dinosaurs. The samples derive from five different localities, and data from embedding sediments are also presented. Additional δ^44/40Ca in skeletal tissues from modern reptiles and birds (avian dinosaurs) were measured for comparison in order to examine whether the original Ca isotopic composition in dinosaur skeletal apatite was preserved or might have changed during the diagenesis and fossilization process.δ^44/40Ca of fossil skeletal tissues range from −1.62‰ (Tyrannosaurus rex enamel) to +1.08‰ (Brachiosaurus brancai bone), while values in modern archosaur bones and teeth range from −1.63‰ (caiman enamel) to −0.37‰ (ostrich bone). The average δ^44/40Ca of the three types of fossil skeletal tissue analyzed - bone, dentin and enamel - show some systematic differences: while δ^44/40Ca in bone exhibits the highest values, while δ^44/40Ca in enamel has the lowest values, and dentin δ^44/40Ca falls in between. Values of δ^44/40Ca in the remains of herbivorous dinosaurs (0.1-1.1‰) are generally higher than those of bones of modern mammalian herbivores (−2.6‰ to −0.8‰) and from modern herbivorous archosaurs, which exhibit intermediate δ^44/40Ca (−0.8‰ to −0.4‰). These systematic isotopic shifts may reflect physiological differences between dinosaurs, mammals and reptiles representing different taxonomic groups of vertebrates.Systematic offsets in skeletal apatite δ^44/40Ca between herbivorous and carnivorous dinosaurs are not obvious, indicating a lack of a clear-cut Trophic Level Effect (TLE) shift between herbivores and carnivores in dinosaurs. This observation can be explained if the carnivorous dinosaurs in this study fed mainly on soft tissues from their prey and did not ingest hard (calcified) tissue to much extent. The most striking indication that the primary δ^44/40Ca is actually preserved in most of the fossil teeth is a difference in δ^44/40Ca of about 0.35 ± 0.10‰ (1SD) between dentin and enamel, based upon 11 of 16 analyzed dentin-enamel pairs. This difference is close to that found in modern reptiles (0.28 ± 0.05‰), and strongly suggests that this tell-tale signature is a primary feature of the fossilized dinosaur material as well. Furthermore, simple mass balance calculations show that changes of the original δ^44/40Ca in bones and teeth by diagenetically-formed calcium-bearing minerals are either small or would require implausible high original δ^44/40Ca values in the skeletal apatite.     

Report on the 4th International Meeting of the IUGS Lower Cretaceous Ammonite Working Group, the “Kilian Group” (Dijon, France, 30th August 2010)

The 4th Kilian Group meeting (Dijon, France, 30th August 2010) focused on the Aptian and Albian Stages. For the Aptian, a two-fold division of the stage was adopted for the Mediterranean area with a boundary between the Dufrenoyia furcata and Epicheloniceras martini Zones. The main changes to the zonal scheme concern the Lower Aptian with: the introduction of a Deshayesites luppovi Subzone in the upper part of the Deshayesites oglanlensis Zone; the replacement of Deshayesites weissi by Deshayesites forbesi as new index-species of the second interval zone; the introduction of a Roloboceras hambrovi Subzone in the upper part of the D. forbesi Zone; and the subdivision of the D. furcata Zone into the D. furcata and Dufrenoyia dufrenoyi Subzones. For the Albian, the upper part of the Douvilleiceras mammillatum Zone (Lower Albian) is now characterized by a Lyelliceras pseudolyelli Subzone. The main amendments concern the Upper Albian. The base of this substage is defined by the base of the Dipoloceras cristatum Zone. Above it, the Upper Albian zonal scheme comprises in stratigraphic order the Mortoniceras pricei, Mortoniceras inflatum, Mortoniceras fallax, Mortoniceras rostratum, Mortoniceras perinflatum and Arrhaphoceras briacensis Zones.     

Sources of Terrestrial Organic Carbon in the Mississippi Plume Region: Evidence for the Importance of Coastal Marsh Inputs

High sedimentation rates along river-dominated margins make these systems important repositories for organic carbon derived from both allochthonous and autochthonous sources. Using elemental carbon/nitrogen ratios, molecular biomarker (lignin phenol), and stable carbon isotopic (bulk and compound-specific) analyses, this study examined the sources of organic carbon to the Louisiana shelf within one of the primary dispersive pathways of the Mississippi River. Surface sediment samples were collected from stations across the inner, mid, and outer Louisiana shelf, within the Mississippi River plume region, during two cruises in the spring and fall of 2000. Lignin biomarker data showed spatial patterns in terrestrial source plant materials within the river plume, such that sediments near the mouth of the Mississippi River were comparatively less degraded and richer in C₄ plant carbon than those found at mid-depth regions of the shelf. A molecular and stable isotope-based mixing model defining riverine, marsh, and marine organic carbon suggested that the highest organic carbon inputs to the shelf in spring were from marine sources (55?C61% marine organic carbon), while riverine organic carbon was the highest (63%) in fall, likely due to lower inputs of marine organic carbon at this time compared with the spring season. This model also indicated that marsh inputs, ranging from 19 to 34% and 3?C15% of the organic carbon in spring and fall, respectively, were significantly more important sources of organic carbon on the inner Louisiana shelf than previously suggested. Finally, we propose that the decomposition of terrestrial-derived organic carbon (from the river and local wetlands sources) in mobile muds may serve as a largely unexplored additional source of oxygen-consuming organic carbon in hypoxic bottom waters of the Louisiana shelf.     

Listric versus planar normal fault geometry: an example from the Eisenstadt-Sopron Basin (E Austria)

In a gravel pit at the eastern margin of the Eisenstadt-Sopron Basin, a satellite of Vienna Basin (Austria), Neogene sediments are exposed in the hanging wall of a major normal fault. The anticlinal structure and associated conjugated secondary normal faults were previously interpreted as a rollover anticline above a listric normal fault. The spatial orientation and distribution of sedimentary horizons and crosscutting faults were mapped in detail on a laser scan of the outcrop wall. Subsequently, in order to assess the 3D distribution and geometry of this fault system, a series of parallel ground penetrating radar (GPR) profiles were recorded behind the outcrop wall. Both outcrop and GPR data were compiled in a 3D structural model, providing the basis for a kinematic reconstruction of the fault plane using balanced cross-section techniques. However, the kinematic reconstruction results in a geologically meaningless normal fault cutting down- and up-section. Additionally, no evidence for a weak layer serving as ductile detachment horizon (i.e. salt or clay horizon) can be identified in stratigraphic profiles. Instead, the observed deflection of stratigraphic horizons may be caused by a displacement gradient along a planar master fault, with a maximum displacement in the fault centre, decreasing towards the fault tips. Accordingly, the observed deflection of markers in the hanging wall—and in a nearby location in the footwall of the normal fault—is interpreted as large-scale fault drag along a planar fault that records a displacement gradient, instead of a rollover anticline related to a listric fault.     

Population biology of Ischyrocerus commensalis,a crab‐associated amphipod,in the Southern Barents Sea: a multi‐annual summer study

Population biology of the amphipod Ischyrocerus commensalis Chevreux, 1900, a facultative commensal of the red king crab Paralithodes camtschaticus (Tilesius, 1815), is here described on samples collected during summers 2005–2009 in Dalnezelenetskaya Bay (Southern Barents Sea, Russia). The studied features included infestation indices, size composition, morphometric, and reproductive parameters of the summer generation. During the studied period, prevalence and mean number of I. commensalis per host were 34.4% and 54.4 ± 3.3 individuals, respectively. The majority of amphipods were found on the host mouth parts, limbs, and gills. The amphipod sex‐ratio was significantly biased towards females (F:M = 1.36:1). The size frequency distributions observed in July and August were similar but in July the proportion of the smallest amphipods (<2.1 mm body length) was two times higher than that in August. All the amphipods with body length >5.1 mm were males or females. Length–weight relationships in female and male amphipods differed significantly, suggesting that females were heavier than the same‐sized males. The females carrying eggs in their brood pouches were the most abundant groups (54.8% in July 2009 and 51.6% in August 2005–2008). The minimal body length of a female which had released juveniles was 7.0 mm in July and 6.2 mm in August. The size at 50% maturity of I. commensalis females was estimated to be 6.58 mm. The number of eggs laid is positively linearly correlated with the size of a female. The proportion of the females with eggs in the latest developmental stage in July was 10 times higher than in August. The differences of biological features in symbiotic amphipods between the July and August may be explained by more intensive reproduction effort in the earlier month.     

Evidence for sediment recirculation on an ebb-tidal delta of the East Frisian barrier-island system, southern North Sea

The Otzum ebb-tidal delta, located between Langeoog and Spiekeroog islands along the East Frisian barrier-island coast, southern North Sea, was investigated with respect to its morphological evolution, sediment distribution patterns and internal sedimentary structures. Bathymetric charts reveal that, over the last 50 years, the size of the Otzum ebb-tidal delta has slightly shrunk, while sediment has accreted on the ebb-delta lobe to the east of the main inlet channel (west of Spiekeroog). Swash bars superimposed on the eastern ebb-tidal shoal (Robben Plate) have migrated south or south-eastwards, i.e. towards the inlet throat. The main ebb-delta body is composed of fine quartz sand, whereas the superimposed swash bars and the inlet channel bed consist of medium-grained quartz sand containing high proportions of coarser bioclastic material. Internal sedimentary structures in short box-cores (up to 30 cm long) are dominated by flood-oriented cross-beds. Longer vibro-cores (up to 1.5 m long) show that, at depth, the sediment is dominated by storm-generated parallel (upper plane bed) laminations with intercalated shell layers and dune cross-bedding. The cross-bedded sands in both box-cores and vibro-cores from the ebb-delta shoal predominantly dip towards the south or southeast, indicating transport towards the inlet throat by the flood current. The observations demonstrate that, contrary to previous contentions, the sediments of the highly mobile swash bars do not bypass the inlet but are instead being continually recirculated by the combined action of tidal currents and waves. In this model, the cycle begins with both fine and medium sands, including shell hash, being transported seawards in the main ebb channel until they reach the shallow ebb-delta front. From here, the sediment is pushed onto the eastern ebb-delta shoal by the flood current assisted by waves, becoming strongly size-sorted in the process. The medium sands together with the shell hash are formed into swash bars which migrate along arcuate paths over a base of fine sand back to the main ebb channel located south of the ebb delta. By the same token, the fine sand between the swash bars is transported south-eastwards by the flood current in the form of small dunes until it cascades into the large flood channel located to the west of Spiekeroog. From here, the fine sand is fed back into the main ebb channel, thus completing the cycle. No evidence was found on the ebb delta for alongshore sediment bypassing.     

Effects of ambient DIN:DIP ratio on the nitrogen uptake of harmful dinoflagellate Prorocentrum minimum and Prorocentrum donghaiense in turbidistat

The effects of varying nitrogen (N): phosphorus (P) ratios on the growth and N-uptake and assimilation of the harmful dinoflagellates Prorocentrum minimum and Prorocentrum donghaiense were examined in turbidistat culture experiments. Algal cultures were supplied with media containing PO34? in various concentrations to obtain a wide range of N:P ratios. Experiments to determine rates of N uptake and assimilation of different N sources (NO3?, NH4+, urea and glycine by P. minimum and NO3?, NH4+ by P. donghaiense) were conducted using 15N tracer techniques at each N:P ratio. The growth rates suggested nutrient limitation at both high and low N:P ratios relative to the Redfield ratio. On a diel basis, the growth of both species was regulated by the light-dark cycle, which may be a result of regulation of both light- dependent growth and light-independent nutrient uptake. Maximum growth rates of both species always occurred at the beginning of light phase. In P-rich medium (low N:P ratio), both species had higher N assimilation rates, suggesting N limitation. Low assimilation coefficients at high N:P ratios suggested P limitation of N uptake and assimilation. NO3? and NH4+ contributed more than 90% of the total N uptake of P. minimum. Reduced N sources were more quickly assimilated than NO3?. Highest average daily growth rates were recorded near an N:P ratio of 12 for both species. The N uptake rates of cultures at N:P ratios near Redfield ratio were more balanced with growth rates. The linkage between growth rates and N uptake/assimilation rates were conceptually described by the variation of cell N quota. The N:P ratios affect the N uptake and growth of Prorocentrum spp., and may regulate their bloom progression in eutrophic ecosystems.