Rossberg landslide history and flood chronology as recorded in Lake Lauerz sediments (Central Switzerland)

The southern slopes of Rossberg mountain, Central Switzerland, on which one of the largest historic landslides of the Alpine region was released in 1806 ad (Goldauer Bergsturz), are prone to large-scale mass wasting processes. This has led to numerous sliding events, which are well-recognizable in the modern topography but lack accurate dating. In order to provide new insights into the timing and the processes associated with past landslides as well as into the frequency of exceptional flood events, long sediment cores were retrieved from the subsurface of Lake Lauerz that lies in the pathway of these landslides and that records strong runoff events with typical flood layers. Analyses of the recovered cores display a sedimentologic succession with variable fingerprints of past landslides and flood events, depending on the coring location within the lake. The landslide signature can be calibrated using the 1806 ad event: An organic-rich peaty unit, which is found in two cores located close to the rockmass impact, points towards a sudden, gravity spreading-induced lateral displacement of the swampy plain where parts of the rock mass were accumulating. This rapid lateral mobilization of soft sediments, and not the rock masses, acted as ultimate trigger for the reported ~15 m-high impulse waves on the lake. In the more distal areas, the 1806 ad event led to the deposition of a thick, organic-rich redeposited layer. The 10 m-long core from the distal basin covers a radiocarbon-dated ~2,000 years sedimentation history and contains a highly similar event layer that was deposited in 810 ± 60 ad. This layer is most likely the product of a major historic landslide, known as Röthener Bergsturz, which, based on scarce historical reports, was commonly dated to 1222 ad. In the 2,000 years record, we identify three periods with enhanced occurrence of flood turbidites dated to 580–850 ad, 990–1420 ad, and 1630–1940 ad. Among the 54 detected flood layers, 6 probably mark exceptionally heavy rainfall events that are dated to ~610, ~1160, ~1290, ~1660, ~1850, and ~1876 ad, the latter being associated to one of the most intense rainfall events ever recorded instrumentally in the region.     

Natural Environmental Changes versus Human Impact in a Florida Estuary (Rookery Bay, USA)

Assessing the impact of climate change and anthropogenic activity on Florida coastal areas requires a thorough understanding of natural climate variability. The available instrumental record, however, is too short and too limited to capture the full range of natural variability. In order to provide additional data on the natural state of the climate system and to evaluate the influence of human impact, we reconstructed climatic and environmental changes of the past 300 years. Pre- (before 1900 ad) and post-human impact conditions were compared in Rookery Bay, a subtropical, southern Florida estuary and its bordering wetland system. Biomarkers from terrestrial and aquatic environments were used to reconstruct temperature, runoff, and aquatic productivity. Pre-anthropogenic conditions before 1750 ad indicate a relatively large contribution of mangrove-derived organic matter, locally decreasing at the end of this period. After 1750 ad follows a relatively stable period in which biomarker concentrations indicate relatively low levels of runoff and aquatic production. Enhanced anthropogenic activities, such as land clearance and hydrological alterations, end this period of stability by altering the hydrological conditions. This leads to a more dynamic system which is more sensitive to disturbances of vegetation and drainage, as evidenced by peak terrestrial biomarker fluxes during the twentieth century. These episodes of enhanced runoff resulted in eutrophication and algal blooms in Rookery Bay. Natural climate phenomena, such as a positive AMO phase and hurricane activity, might have added to ongoing processes during the twentieth century.     

Species of plated dinosaur Stegosaurus (Morrison Formation, Late Jurassic) of western USA: new type species designation needed

Stegosaurus armatus Marsh 1877, based on a partial tail and a very large dermal plate from the Morrison Formation (Late Jurassic) of Morrison, Wyoming, USA, is a nomen dubium. Valid Morrison stegosaur species (with possible autapomorphies, dermal “armor” considered if present), with most holotypes consisting of a disarticulated partial postcranial skeleton at most, include: Hypsirhophus discurus Cope 1878 (characters of incomplete vertebrae, a dorsal and a caudal; Garden Park near Cañon City, Colorado); Stegosaurus ungulatus Marsh 1879 (half skeleton with partial skull; three pairs of small flat dermal spines adjacent to terminal tail spikes; Quarry 12, Como Bluff near Como station, Wyoming; syntype is holotype of S. duplex Marsh 1887, half skeleton lacking armor; Quarry 11, Como Bluff); Diracodon laticeps Marsh 1881b (just partial dentaries with few teeth, diastema between predentary and tooth 1; Quarry 13, Como Bluff); Stegosaurus sulcatus Marsh 1887 (pair of ?tail spikes with greatly enlarged base; Quarry 13, Como Bluff); S. longispinus Gilmore 1914 (characters of distal caudal vertebrae, tail spikes: two pairs, sub-equal bases, transversely flattened, very elongate; Alcova, Wyoming); and Hesperosaurus mjosi Carpenter, Miles &; Cloward, 2001 (?Stegosaurus mjosi; partial articulated skeleton with skull, no limbs, several plesiomorphic and autapomorphic characters, dorsal plates longer than tall; Wyoming). However, the well known valid nominal species, S. stenops Marsh 1887 (12 autapomorphies, three alternating flat plates adjacent to terminal tail spikes; Garden Park), is based on a virtually complete articulated skeleton lacking only the terminal caudal vertebrae and first pair of tail spikes. It includes 17 dermal plates, is still exposed as preserved on the block, and is the current basis for Stegosaurus. The International Commission on Zoological Nomenclature (ICZN) will be petitioned to designate S. stenops Marsh 1887 as the new type species of Stegosaurus Marsh 1877 in order to conserve Stegosauria Marsh 1877 and Stegosauridae Marsh 1880 (also Stegosauroidea, Stegosaurinae).     

Sub-seasonal scale fluctuations of theITCZ over the Indo-Pacific region during the summer monsoon season. Part I: Features over the Indian region

Monex-79 andISMEX-73 data have been analysed to study the sub-seasonal scale fluctuation of near equatorial oceanic intertropical convergence zone (ITCZ) over the North Indian ocean during the summer monsoon of 1979 and 1973. The oceanicITCZ is characterised by a narrow shear zone between the equatorial westerlies and the tropical easterlies, associated with organised convective clouds. Synoptic analysis presented in this paper shows the steady northward propagation of the oceanicITCZ from its near equatorial position (5–10°N) to the continental position (20–25°N) during the onset and mid-season revivals of monsoon after breaks. The northward propagation is initiated by the strengthening of the equatorial westerlies which result in the intensification of the shear zone and the embedded disturbances. The establishment of the northward propagating mode near normal monsoon trough position over the continent characterises the active phase of monsoon. As the monsoon cycles from active to weak/break phase, the monsoon trough (continentalITCZ) dissipates near the foothills of the Himalayas and the oceanicITCZ gets emphasised once again near the equatorial region. The major phase changes in theITCZ occur at an interval of about 30–50 days which dominantly control the intra-seasonal fluctuation of the Indian summer monsoon. The paper also discusses the characteristic features of the oceanicITCZ during different phases of the monsoon.     

Alpha-radioactivity-related upper age limit for thermoluminescence dating?

A systematic underestimation of the age of mineralisation by the thermoluminescence (tl) technique has been observed in a variety of samples older than Quaternary although their naturaltl was not saturated. The samples included calcites, oozes, lime stones, shales, gypsum, basalts and dolerites. It is shown that thetl build-up in nature reaches a dynamic equilibrium level much ahead of the lifetime of thetl trap concerned and is solely determined by the alpha radioactivity of the sample; the validity fortl dating does not exist once such an equilibrium is reached. For the samples considered, the limiting Paleo-alpha dose fortl dating validity works out to be about 150 kilorads; beyond this dose, thetl age and the geological age bears a ratio given by \(t'/t = a\left[ {\smallint _0^t \dot D_\alpha dt} \right]^{ - b} \) wherea andb are constants and \(\dot D_\alpha \) is the annual alpha irradiation rate in the sample. For a suite of samples withb≠1, relative dating seems possible by thetl technique. It may be generalised that samples with 1ppm level of U, Th content cannot betl dated if they are older than about 500 kiloyears even though theirntl trap lifetimes may be 100 myrs; conversely, a 1000 myr-old sample can betl dated only if its U, Th content is much less than ppb levels and itstl trap lifetime greater than 10¹⁰ years.     

Dienerian (Early Triassic) ammonoids from the Candelaria Hills (Nevada, USA) and their significance for palaeobiogeography and palaeoceanography

A well-preserved ammonoid fauna of Early Dienerian age has long been known from the lower portion of the Candelaria Formation in the old Candelaria silver mining district in Mineral and Esmeralda Counties, Nevada, but for a number of reasons, this fauna has never been studied in detail nor illustrated. Previous authors assigned this ammonoid fauna to the Early Dienerian Proptychites candidus Zone of Canada. In reality, it more closely resembles the Tethyan faunas than the higher palaeolatitude Canadian faunas, thus indicating the presence of some degree of equatorial faunal exchange between opposite sides of the Panthalassic Ocean during Early Dienerian time. It also indicates the onset of a provincialism, which contrasts with the cosmopolitan Griesbachian faunas. A rigorous taxonomic analysis of the Candelaria fauna allows us to differentiate the following ten species, which include two new species and one new genus (Mullericeras nov. gen.) belonging to the new family Mullericeratidae: Ambites lilangensis (Krafft, 1909), Ambites aff. radiatus (Brühwiler, Brayard, Bucher and Guodun, 2008), Ussuridiscus sp. indet., ??Koninckites?? aff. kraffti Spath, 1934, Mullericeras spitiense (Krafft, 1909), Mullericeras fergusoni nov. sp., Mullericeras sp. indet., Proptychites haydeni (Krafft, 1909), Proptychites pagei nov. sp., Vavilovites sp. indet. and Parahedenstroemia kiparisovae Shigeta and Zakharov, 2009. This Early Dienerian fauna correlates with the Ambites fauna known from the base of the Ceratite Marls in the Salt Range and from the base of the ??Meekoceras?? beds in Spiti (northern Gondwanian margin). The fauna also permits the precise dating of a shelfal anoxic episode on the equatorial North American margin. This anoxic event correlates in time with similar palaeoceanographic changes in the southern Tethys, which indicates that the Early Triassic biotic recovery was at least partly shaped by such discrete, short events rather than by pervasive and lingering adverse environmental conditions.     

Geologic urban hindplanning: An example from a hellenistic-byzantine city,stobi, Yugoslavian macedonia

Stobi flourished between about 400b.c. anda.d. 600, and, like modern cities, was afflicted by several environmental-geologic difficulties. A large Christian church was built upon poorly compacted artificial fill, resulting in severe foundation problems. An earthquake did extensive damage to the Roman theatre between two stages of its construction. A catastrophic mudflow destroyed structures lying below a cliff of flysch sandstone and shale. After the third or fourth centurya.d. severe desiccation of the climate set in, leading to devegetation, flooding, and dust storms. Structures on the flood plain were buried in several meters of fine sediment. Stobi finally was abandoned, and the structures eventually were buried by wind-blown dust accumulating at the rate of about 1 meter per millenium.     

A new ophiuroid (Geocoma schoentalensis sp. nov.) from the Middle Jurassic of northwestern Switzerland and remarks on the family Aplocomidae Hess 1965

A new ophiuroid species from the Hauptrogenstein Formation (Middle Jurassic, Bajocian) of the Rehhag ridge near Schöntal, northwestern Switzerland, is described based on 34 specimens. The impression of an indeterminate astropectinid sea star has also been found. The fully articulated specimens have been smothered by mobile oolitic dunes or sandwaves. The site can be genetically classified as an obrution deposit and belongs to the widely recognized “Hauptrogenstein type”. The remains are assigned to the genus Geocoma d’Orbigny 1850, best known from the type species, G. carinata (Münster), from the Tithonian Plattenkalk of Zandt. As suggested by Kutscher (1997) this species also includes Ophiocten kelheimense Boehm 1889, now documented by numerous well-preserved specimens from the Plattenkalk of Hienheim. Kutscher assigned the Hienheim specimens to the genus Sinosura Hess 1964 and used both names though G. carinata has priority. Despite rather small differences Sinosura is retained as a valid genus besides Geocoma, and both are placed in the family Aplocomidae Hess 1965. Geocoma and Sinosura share small adpressed arm spines with Aplocoma d’Orbigny 1852. Aplocoma is represented by a number of Triassic and Jurassic species, and the subfamily Aplocominae is proposed herein for the three genera. A second subfamily, Ophiopetrinae, is proposed for the genera Ophiopetra Enay &; Hess 1962 and Ophiohybris Hess 1964, and is characterized by larger, erect arm spines.     

Migration of the dip equator in the Indian region

The position of the dip equator (de) is worked out in the Indian region based on fairly close geomagnetic measurements made during a survey in the year 1981. Thede is located about 24 km south of its 1971 position along the 77·5°E meridian. Also, thede positions for the epochs 1971 and 1981 show closeness on the east coast of India when compared to its west coast positions. Thede positions inferred from the repeat observations since 1909 are used for estimating the pattern of migration and the results are discussed.     

Photogrammetric survey of the structural geology of the Sudbury-McGregor Bay District,Ontario, Canada

New information is presented regarding the structural geology of the Huronian rocks (Middle Precambrian) of the Sudbury-McGregor Bay district of Ontario, Canada. Using standard photogrammetric techniques a base map of the area was prepared from photographs taken at a height of about 11,000 m. Extrapolation from the work ofYoung &Church (1966) together with the evidence deduced from the aerial photographs facilitated the construction of a lithological map at the scale of 1∶187,500 (Fig. 2). From this map large scale type 2 interference pattern is recognised (seeRamsay, 1967) and a tentative structural history is suggested for the area.     

Chlorit-Hornblende-Felse des Bergsträßer Odenwaldes und ihre Phasenpetrologie

Ultrabasic metamorphic rocks with typical mineral assemblage of cummingtonitic hornblende+Mg-chlorite+talc (described byMatthes u.Okrusch, 1965, and called “hösbachit”) were found for the first time in Odenwald/Germany. Three steps of metamorphic development can be described: the primary magmatic ultrabasic rock consisted of (1) orthopyroxene (bronzite), clinopyroxene (diallage), poikilitic olivine, and some hornblende. This is indicated by textural relicts, structural and geochemical investigations. A regional metamorphic process under conditions of the staurolite-almandine-subfacies ofWinkler’s andTurner andVerhoogen’s almandine-amphibolite facies transformed this assemblage to (2): cummingtonitic hornblende I+Mg-chlorite I (clinochlore)+talc. The third step followed under more diaphthoritic conditions and brought mineral assemblage (3): tremolitic hornblende II+Mg-chlorite II (pennine)+talc.     

Experimental investigation of the reaction forsterite + H2O ⇌ serpentine + brucite

A new determination of the equilibrium reaction: $$\begin{gathered} 2{\text{ Mg}}_{\text{2}} [{\text{SiO}}_{\text{4}} ] + 3{\text{ H}}_{\text{2}} {\text{O}} \rightleftharpoons {\text{1 Mg}}_{\text{3}} [({\text{OH)}}_{\text{4}} |{\text{Si}}_{\text{2}} {\text{O}}_{\text{5}} ] + 1{\text{ Mg(OH)}}_{\text{2}} \hfill \\ \hfill \\ {\text{ forsterite serpentine brucite}} \hfill \\ \end{gathered} $$ yielded equilibrium temperatures which lie (at identical H₂O-pressures) about 60° C lower than all previously published data (Bowen and Tuttle, 1949; Yoder, 1952; Kitahara et al., 1966; Kitahara and Kennedy, 1967). It has been shown that the above authors have determined not the stable equilibrium curve but instead a metastable “synthesis boundary”. The actual (stable) equilibrium curve is located at 0,5 kb and 350° C 2,0 kb and 380° C 3,5 kb and 400° C 5,0 kb and 420° C 6,5 kb and 430° C.     

Comparison of electron density models with incoherent scatter radar observations at the equator

This paper points out certain discrepancies when the incoherent scatter radar observations at Jicamarca and the electron density models, (the Bent andiri) were compared. In all cases the bottomside semi-thickness of the observed profile was significantly greater than that of both Bent andiri models. The decay constants associated with the topside ionosphere for the observed profiles were generally greater than that of the two models, the difference being more pronounced in theiri model. The results call for a revision of the models so that they accurately represent the electron density distribution at the equator.     

Comparison between “magnetic” and sedimentary fabric in graded and cross-laminated sand layers,Southern California

Paleocurrent directions can be reconstructed by determining optically the preferred orientation of longest grain axes of sediments; this can be estimated by measuring the anisotropy of magnetic susceptibility (Rees, 1965). In order to check the applicability of both methods, the orientation of large- and small-scale sedimentary structures (cross-bedding, sole markings, grain orientation) was compared with the “magnetic fabric” of some sand and silt layers of different ages and origins:

1. Rosario Formation (Late Cretaceous), La Jolla: thin siltstone layers with small-scale current-ripple cross-lamination;
2. Monterey and Topanga Formations (Miocene, Los Angeles Basin): graded and laminated sandstone beds (“turbidites”);
3. Holocene submarine La Jolla Fan: graded and cross-laminated sand layers (Rees, v.Rad &Shepard, 1968).

Most of the investigated sand layers have a “primary-style” magnetic fabric, characterized by well-grouped, horizontal maximum susceptibility axes, sometimes slightly imbricated upcurrent, minimum susceptibilities normal to the bedding, and intermediate values of the factor q (about 0.1–0.5), suggesting moderately strong current conditions during deposition. The orientation of maximum susceptibility axes correlates with the directions of sand transport, inferred from cross-lamination foresets and sole markings (a). Also conventional optical grain orientation measurements give very similar directions as maximum susceptibilities (b). In Recent deep-water sand layers (c) cross-lamination foresets and maximum susceptibility axes are parallel, and influenced by the local morphology (e. g. fan-valley axis). Since current-parallel orientation of the longest grain axes and maximum susceptibility axes is prevailing in deep-water sands, the magnetic method is a useful tool for palcocurrent analysis. Characteristic differences of the magnetic fabrics from different depositional environments may also give clues to the mechanisms of sediment transport.     

Crustal Structure of the Benue Valley Area (Nigeria)

The regional positive anomaly recorded over the Benue Trough (Cratchley &Jones, 1965) is here interpreted to have resulted from uplift of 10 to 12 kilometres of the mantle. The uplift was due to spreading of the crust and contemporaneous thinning of crustal material.     

Precision,accuracy and meaning of fission track ages

The precision, meaning, and accuracy of the fission track (ft) dating method are reviewed from an examination of the recent literature as well as previously unpublished data from the author's laboratory. It is concluded that forapparent ft ages (i.e. ages derived from the canonical age equation) a precision (2σ level) of the order of ±4% to ±5% can be reached provided that (i) uranium is sufficiently homogeneously distributed in the dated samples, at least locally; and (ii) a large enough number of tracks can be counted. Model ft ages,i.e. ages for which partial geological track annealing is taken into account, have variable degrees of precision. While model ages obtained with the track-size method seem, as evaluated from the literature, to have usually a limited precision of the order of ±30% (2σ), plateau ages usually have a precision better than ±5% at a 2σ confidence level. Because it provides an objective test on the accuracy of track identification, as well as some insight of the variability of closing temperatures between various samples of a given mineral phase, the Isochronal Plateau (icp) method, when applicable, will be preferred (Poupeauet al 1980a). However, for phases which could be damaged by heating at relatively high temperatures, as for example hydrated glass shards from tephra, an Isothermal Plateau (itp) approach is to be preferred. Due to uncertainties about the value of the²³⁸U spontaneous fission decay constant λ _f as well as difficulties inherent in the dosimetry of thermal neutrons in nuclear reactors, theft method of dating is not an independent one. Presently, it relies on the existence of geological standards (volcanic rocks) of known age, allowing to determine anoperational ‘λ _f ’ value (Naeseret al 1980). Accordingly, the accuracy of anft age is limited by the accuracy on the age of the standard. It should be better than ～5%. For volcanic, hypovolcanic rocks, and shallow intrusives, theft method dates the time of formation, provided they were not further reheated. More generally, the track method providescooling ages. Closing temperatures calculated from laboratory experiments vary from ?300°C to 100°C, according to minerals, for slow cooling rates (～1°C/m.y.). For apatites, recent geological calibrations (Naeseret al 1980; Gleadow and Duddy 1980) confirmed laboratory extrapolations. The association of theft method with other geochronometers is therefore critical to the study of the cooling history of old cratons as well as to the evaluation of uplift/erosion rates in recent belts.     

Quasi-biennial oscillation in geomagnetic disturbance field

Using the techniques of second derivatives, digital filtering and power spectral analysis, the fine structure of the quasi-biennial oscillation (qbo) in the equatorial geomagnetic field in the Indian zone is studied. The salient results are: (i) in the quiet day field,qbo is weak and the signal strength has no local time dependence; (ii) in the disturbance field the signal is strongest in the afternoon and evening hours and (iii) larger magnitudes are manifested closer to the dip equator. The difference in dawn and dusk amplitudes of the signal and the absence of significant strength close to noon in the electrojet region rules outeuv flux as the responsible agent.     

Basal flow rate of Changme-Khangpu glacier,Sikkim Himalaya based on32Si and210Pb chronology

Using environmental radioisotopes silicon-32 and lead-210, the radiometric ages of ice at the surface and at 5 m depth at the snout of the Changme-Khangpu (ck) glacier have been calculated to be 100 and >650 years respectively. Based on i) these age estimates, ii) a net uniform accumulation rate of 0·7 m/yr of ice in the accumulation zone; and iii) applying a simple ice flow model assuming melting of ice of 1 cm/yr at the base of the glacier, it is demonstrated that the average basal flow rate of theck glacier is much smaller (at least by a factor of three) than that of 40 m/yr estimated for the surface ice. This observation is in good agreement with the earlier work on basal flow rates and indicates that the deeper ice near the bed rock travels much slower than the surface ice.     

Power spectrum analysis of geomagnetic indices

Using the method of maximum entropy spectral analysis (MESA) by Burg and the least-squares linear prediction (lslp) (also calledFABNE) by Barrodale and Erickson, the spectra of geomagnetic indices Ap, AN, AS, AE, AU, AL, Dst and cosmic ray neutron intensity at Deep River are obtained for 1965 and 1969 from daily means and for longer periods from monthly means. A large number of peaks of periodicities from 2 days to several years is obtained, many of which are shown by all the indices. Some of these are probably harmonics of the 27 days solar rotation period and the 20–22 years double sunspot cycle period. Comparison is made with results of earlier workers who reported fewer peaks.     

Kimmeridgian protoglobigerinids (Foraminifera) from Crussol (SE France)

A detailed investigation of the protoglobigerinids from the Kimmeridgian section of the Montagne de Crussol, SE France is presented. This monotonous succession of predominantly carbonate beds represents peri-platform hemipelagic deposits, well dated by ammonites. Three species were determined in thin sections and in isolated forms after extraction by acetolysis. Favusella? parva (Kuznetsova) is the most common species occurring in almost the entire succession from the Orthosphinctes to the Beckeri zones. Favusella hoterivica (Subbotina) has been retrieved less frequently from the Platynota to the Beckeri zones, and it is its oldest occurrence. The rare Globuligerina bathoniana (Pazdrowa) occurs only in the Late Kimmeridgian. Based on our study and the review of the literature a palaeogeographical map was plotted, showing that most of the protoglobigerinid occurrences are in deep water facies of the northern margin and central part of the Tethys. These records demonstrate the presence of Globuligerina bathoniana, G. oxfordiana (Grigelis), Favusella hoterivica, F.? parva and Compactogerina stellapolaris (Grigelis) in the Kimmeridgian.