Evolution and strike variability of early post-rift deep-marine depositional systems: Lower to Mid-Cretaceous, North Viking Graben, Norwegian North Sea

The controls and development of early-post-rift, deep-water depositional systems are poorly understood due to their commonly deeply-buried nature. As a consequence, in the subsurface there is usually a lack of well penetrations and/or weak seismic imaging. At outcrop, early post-rift strata have commonly been deformed beyond reasonable recognition by later inversion tectonics. In contrast to these systems, the North Viking Graben shows a well-imaged Cretaceous early post-rift package with good well control and little effect from inversion. Therefore, this paper examines the early post-rift, deep-water depositional systems of the North Viking Graben to determine the controls on their stratigraphic position, geometry and evolution, and thus provide an analogue for comparable systems. Greater understanding of such systems will allow for the enhanced prediction of reservoir units in the subsurface and development of new play models since post-rift intervals are generally under-explored.The basin configuration inherited by the Cretaceous early post-rift in the northern North Sea was set up by Permo-Triassic and Late Jurassic rifting. In the North Viking Graben this established considerable along-strike variability, resulting in a northern basin segment surrounded by steep slopes and faulted-bounded structural highs and a southern basin segment margined by slopes with noticeably gentler gradients. Associated with the Cretaceous post-rift is an overall transgressional trend, which drowned local source areas, resulting in prevalent carbonate and hemipelagic mudstone deposition in the basins. In the North Viking Graben, the uplifted Oseberg fault-block provided the sub-aerial clastic source area until it was submerged in the early Upper Cretaceous.The early post-rift infill of the North Viking Graben was divided into four key seismic stratigraphic units (K1, K2, K3 and K4) using an integration of seismic and well data. Inside this stratigraphic framework, the depositional systems within each K-unit were resolved from characteristic seismic facies, amplitude anomalies, relationship with adjacent reflections, and geomorphologies. In the northern basin segment, the early post-rift stratigraphy contains basin-floor fans, a channel complex and a shoreline-like geometry, whereas the southern basin segment is solely characterised by hemipelagic and carbonate deposition. This spatial variability indicates that one of the dominant controls on the development of the early post-rift depositional systems in the North Viking Graben was the inherited syn-rift fault-controlled topography. The steep slopes bounding the northern basin segment aided the delivery of sediment from the sub-aerial Oseberg source area to the graben whereas the submerged, gentle slopes in the southern basin segment were relatively sediment-starved.Long- and short-term changes in relative sea-level also heavily influenced the evolution of the early post-rift basin stratigraphy. Short-term relative sea-level fall allowed basin-floor fan emplacement whereas short-term relative sea-level stand-still favoured deposition of a channel complex. Deposition of the shoreface-like geometry is associated with a short-term relative sea-level rise. This temporal difference in the style and scale of the depositional systems is also interpreted to reflect the gradual denudation and drowning of the Oseberg source area. Regional short-term trangressive and anoxic events in the northern North Sea further influenced the early post-rift strata, resulting in the deposition of stratigraphic units that can be correlated across the North Sea.     

Osmotic suction of highly plastic clays

This paper presents a study on osmotic suction of compacted highly plastic clays. Two different types of bentonite (i.e. Calcigel and a bentonite from India called herein as Indian bentonite) were used. Squeezing technique was utilized to obtain soil pore-water of the specimen. Using relationship between electric conductivity and osmotic pressure of salt solution, osmotic suction of soil pore-water was obtained. Additional tests (i.e. total and matric suction using filter paper method and swelling pressure using constant volume swelling pressure test) were performed. The results show that osmotic pressure of soil pore-water obtained decreases by increasing squeezing pressure. Based on experimental result, osmotic suction of the specimen is osmotic pressure of the first drop of extracted soil pore-water. An empirical method was suggested to determine the squeezing pressure in squeezing technique. In addition, roles of osmotic suction in thermo-hydro-mechanical behavior of highly plastic clays were presented and discussed in the paper.     

Timescales of geological processes: Preface

正1. Introduction One of the major challenges in Geoscience is to understand how the formation and evolution of the Earth System are governed by timescales e that is, how the various geological processes that continue to contribute to its present-day structure and composition operated in the deep past. The traditional view of such processes refers to events that occur at immense spatial scales and over hundreds of millions of years, constrained in most cases by the ages of rocks determined using isotopic dating methods or the fossil record. However, the modern view of geological processes has increasingly acknowledged that their durations can be significantly shorter than previously thought possible, or indeed detectable     

Morphological characteristics, formation and glaciological significance of Rogen moraine in northern Scotland

Rogen moraine are enigmatic landforms whose exact origin is still debated. We use NEXTMap digital surface models and aerial photographs to map the distribution of previously unreported fields of Rogen moraine in the vicinity of Loch Shin, northern Scotland. Existing models of formation are tested against detailed morphological Rogen moraine characteristics obtained from the remote sensing data and field observations. Detailed morphometric analyses combined with their geographical setting lead us to postulate a likely mechanism of formation. Rogen moraine appear to have formed in areas where there were strong basal ice-flow velocity gradients. Thrusting by compression, or fracturing by extension of preexisting partially frozen sediment probably occurred in these areas, resulting in Rogen moraine formation. A general down-ice increase in ridge crest spacing suggests that the latter process may have been dominant, and is consistent with the location of Rogen moraine in the lee of topographic obstructions, in areas that experienced overall extensional ice flow. We also suggest that at least one field of Rogen moraine formed where lateral basal ice-flow velocity gradients were strongest — possibly in a subglacial shear margin setting. Given their location, the landforms may be consistent with formation during headward scavenging of the Moray Firth palaeo-ice stream into a shrinking core of cold-based ice.     

LBT: Its Instrumentation and Key Science Projects

B25 The site testing for the Thirty Meter Telescope and its potential role in developing the shortterm forecasting of observing conditions B34 LUCIFER: a NIR Spectrograph and Imager for the LBT B41 PEPSI: the Potsdam Echelle Polarimetric and Spectroscopic Instrument for the Large Binocular Telescope B44 LUCIFER: High Redshift Science Cases B49 Feedback in galaxy cores: a LBT Key Science Project proposal B52 SERPIL/LIINUS: a design study for a Near‐Infrared Interferometric Integral Field Spectrometer for the LBT B64 The Construction of the Large Binocular Telescope B73 Operating the LUCIFER Instrument B85 M92 – a crucial testbed for atomic diffusion and mixing in stars B142 The Large Binocular Camera at LBT B148 LUCIFER and its Exposure‐Time‐Calculator B196 The Multi‐Object Double Spectrograph and Nulling Interferometer for the Large Binocular Telescope B199 The Laser Guide Star Facility for the LBT B231 The PEPSI “deep spectrum” project B236 Zeeman‐Doppler imaging from Stokes IQUV line profiles B257 D3Dnet: getting ready for MUSE, a 2nd Generation Instrument for the VLT     

Metal tissue levels in Steller sea lion (Eumetopias jubatus) pups

The endangered Western population of the Steller sea lion declined for three decades for uncertain reasons. We present baseline data of metal concentrations in pups as a first step towards investigating the potential threat of developmental exposures to contaminants. Seven metals were investigated: arsenic, cadmium, silver, aluminum, mercury, lead and vanadium. Vanadium was detected in only a single blubber sample. Mercury appears to be the most toxicologically significant metal with concentrations in the liver well above the current action level for mercury in fish. The concentrations of aluminum, arsenic, silver, cadmium and lead were present in one-fourth to two-thirds of all samples and were at either comparable or below concentrations previously reported. Neither gender nor region had a significant effect on metal burdens. Future work should consider metal concentrations in juveniles and adults and toxicological studies need to be performed to begin to assess the toxicity of these metals.     

The Western Bohemia/Vogtland Region in the Light of the Webnet Network

The local network of digital seismic stations WEBNET monitors the seismic activitv of practically the whole region of Western Bohemia/Vogtland swarms. The network consists of ten short-period stations and one very broadband station. The paper describes the configuration of the network, instrumental equipment and the basic parameters of the stations. The method of and formula for computing the local magnitudes from the WEBNET and KRASLICE seismograms are also given. Based on continuous WEBNET observations in the period 1995-1999, we were able to improve the model of temporal and spatial energy release in the region, the principal characteristics of which are summarised in the paper. Apart from direct P and S waves, the WEBNET seismograms also contain other significant P- and S-type waves, provisionally interpreted as reflected PxP, SxS and SxP waves. The fundamental characteristics of these waves are given in the paper, and tentative mechanisms of their origination are discussed. The large residua in the travel times of the P and S waves, and the discrepancies in the seismograms recorded at stations located east of the principal focal zone are pointed out.     

Refined Locations of The Swarm Earthquakes In The Nový Kostel Focal Zone and Spatial Distribution of The January 1997 Swarm In Western Bohemia,Czech Republic

In order to improve the accuracy of the spatial distribution of earthquake foci in the principal Novy Kostel focal zone, refined focal locations of about 1500 micro-earthquakes of the 1991 – 1997 period were determined using the relative Master-Event location method. To estimate the reduction in the scatter of located hypocentres, the results were compared with those obtained by routinely used FASTHYPO method and cluster analysis (the nearest-neighbour method) was applied to the located foci to evaluate the spatial distribution of the foci. Based on the results of refined location and of the cluster analysis, a concept of seismic energy release in space and time in the main focal zone was developed. Especially the January 1997 earthquake swarm was studied in detail: 946 events were located with the Master-Event location method, and the dimensions and geometry of focal clusters were determined. Type analysis was applied to waveforms to divide approximately 800 located events into eight multiplet groups to each of which a characteristic source mechanism was assigned. The spatial distribution of the foci as well as of the eight types of source mechanisms was revealed in this way and also the planes fitting the clusters of foci with two predominant source mechanisms were determined fairly well.