Principles of Engineering Geology

Attewell, P. B.; Farmer, I.W.

doi:10.1007/978-94-009-5707-7

Cited by 146 publications

(62 citation statements)

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“…These sedimentation rates served to calculate mass accumulation rates for phosphorus by multiplying [P] mg/g by the sedimentation rate (cm/ka) and rock density (Attewell and Farmer, 1976).…”

Section: Methodsmentioning

confidence: 99%

Organic carbon deposition and phosphorus accumulation during Oceanic Anoxic Event 2 in Tarfaya, Morocco

Mort

Adatte

Keller

et al. 2008

Cretaceous Research

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a b s t r a c tWith a multi-proxy approach, an attempt was made to constrain productivity and bottom-water redox conditions and their effects on the phosphorus accumulation rate at the Mohammed Plage section on the Tarfaya coast, Morocco, during the Cenomanian-Turonian Anoxic Event (OAE 2). A distinct d 13 C org isotope excursion of þ2.5& occurs close to the top of the section. The unusually abrupt shift of the isotope excursion and disappearance of several planktonic foraminiferal species (e.g. Rotalipora cushmani and Rotalipora greenhornensis) in this level suggests a hiatus of between 40-60 kyrs at the excursion onset. Nevertheless, it was possible to determine both the long-term environmental history as well as the processes that took place immediately prior to and during OAE 2. TOC% values increase gradually from the base of the section to the top (from w2.5% to w10%). This is interpreted as the consequence of a longterm eustatic sea-level rise and subsidence causing the encroachment of less oxic waters into the Tarfaya Basin. Similarly a reduction in the mineralogically constructed 'detrital index' can be explained by the decrease in the continental flux of terrigenous material due to a relative sea-level rise. A speciation of phosphorus in the upper part of the section, which spans the start and mid-stages of OAE 2, shows overall higher abundances of P reactive mass accumulation rates before the isotope excursion onset and lower values during the plateau. Due to the probable short hiatus, the onset of the decrease in phosphorus content relative to the isotope excursion is uncertain, although the excursion plateau already contains lower concentrations. The C org /P total and V/Al ratios suggest that this reduction was mostly likely caused by a decrease in the available bottom oxygen content (probably as a result of higher productivity) and a corresponding fall in the phosphorus retention ability of the sediment. Productivity appears to have remained high during the isotope plateau possibly due to a combination of ocean-surface fertilisation via increased aridity (increased K/Al and Ti/Al ratios) and/or higher dissolved inorganic phosphorus content in the water column as a result of the decrease in sediment P retention. The evidence for decreased P-burial has been observed in many other palaeoenvironments during OAE 2. Tarfaya's unique upwelling paleosituation provides strong evidence that the nutrient recycling was a global phenomenon and therefore a critical factor in starting and sustaining OAE 2.

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Section: Methodsmentioning

confidence: 99%

Organic carbon deposition and phosphorus accumulation during Oceanic Anoxic Event 2 in Tarfaya, Morocco

Mort

Adatte

Keller

et al. 2008

Cretaceous Research

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“…6). The rock densities for black shales, marls, cherts and limestones were taken from Attewell and Farmer (1976). To avoid a different mass accumulation rate for the same sample, the following corrections were applied.…”

Section: Sedimentation and Mass Accumulation Ratementioning

confidence: 99%

The Cenomanian/Turonian anoxic event at the Bonarelli Level in Italy and Spain: enhanced productivity and/or better preservation?

Mort

Jacquat

Adatte

et al. 2007

Cretaceous Research

191

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The upper Cenomanian pelagic sediments of Furlo in the northern Apennines, Italy, are characterized by a 1.5-m-thick organic-rich stratigraphic horizon called the Bonarelli Level, which represents the second major oceanic anoxic event in the Cretaceous (OAE 2). The Bonarelli Level is depleted in carbonates and consists essentially of biogenic quartz, phyllosilicates, and organic matter, with values of TOC reaching 18%. The age of the Furlo section is constrained by correlating its d 13 C curve with that of the well-dated Pueblo (USA) and Eastbourne (UK) sections. The presence of all the planktonic foraminiferid zones and details of the OAE 2 d 13 C excursion indicates a relatively continuous but reduced sedimentation rate across the Cenomanian/Turonian (C/T) boundary. Sediment and TOC mass accumulation rates have been calculated and suggest a sedimentation break in the upper Bonarelli Level. This may be an artifact of the diachronous FAD of the planktonic foraminiferid Helvetoglobotruncana helvetica and suggests that in some sections the d 13 C curve may provide more reliable age control for dating the C/T boundary. In order quantitatively to explain the carbon isotope curve and the measured TOC mass accumulation rate, a simple dynamic model of the isotope effects of organic versus inorganic carbon burial was developed. In order to verify the consistency of the model we correlated the modeled output of the Furlo section with that of the Manilva section, in southeast Spain. The modeling shows that increasing productivity only partially explains the measured d 13 C excursion and is not the only factor relevant to black shales deposition. Preservation may play a central role, especially in the later stages of OAE 2. Phosphorus and TOC accumulation patterns in the Bonarelli Level in both Furlo and Manilva suggest a similar process although other factors may also be involved.

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“…These processes cause changes in the physical and mechanical properties. Mechanical weathering also influences the chemical weathering of flysch components [9]. Fine-grained fractions, such as siltstones, are the most affected by chemical weathering.…”

Section: Geological Properties and Regional Distribution Of Flysch Dementioning

confidence: 99%

“…Through this gradual degradation, the physical and mechanical properties of clayey silt materials become more like engineering soil. A consequence of these types of geomorphological processes is a sporadic accumulation of eroded Quaternary deposits on the slopes that can be susceptible to sliding [8][9][10]. In a typical situation, the flysch bedrock is covered by these Quaternary deposits, except the isolated areas where the erosion is more expressed.…”

Section: Geological Properties and Regional Distribution Of Flysch Dementioning

confidence: 99%

Landslide susceptibility analyses in flysch areas in the north-eastern part of the Adriatic coast

Dugonji¹,

Jovan²,

Arbanas³

et al. 2012

Risk Analysis VIII

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Many different instability phenomena were found on flysch slopes in the past 30 years in the area of dominant geomorphological unit Rječina Valley -Sušačka Draga Valley -Bakar Bay -Vinodol Valley. This paper gives the review of present landslide appearances and the estimation of the possible landslide occurrence at the NW part of Vinodol Bakarac Valley, between the Bakarac and Križišće settlements, in the Kvarner area (north-eastern Croatian Adriatic coast). Based on longtime investigation work results for different purposes it was established that the wings and the base of the valley are made of flysch rock complex, consisting mainly of silty marl, laminated siltstones and fine grained sandstones near the contacts with karstified carbonate rock mass. Landslide susceptibility analysis of this area was made based on existing data about lithological composition and geological fabric, geotechnical properties of slope deposits and flysch bedrock, hydrological and hydrogeological conditions and existing landslides inventory map. Spatial analysis of unfavorable conditions in the investigated location resulted in landslide susceptibility map which divides the area into four classes of susceptibility.

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Principles of Engineering Geology

Cited by 146 publications

References 0 publications

Organic carbon deposition and phosphorus accumulation during Oceanic Anoxic Event 2 in Tarfaya, Morocco

Organic carbon deposition and phosphorus accumulation during Oceanic Anoxic Event 2 in Tarfaya, Morocco

The Cenomanian/Turonian anoxic event at the Bonarelli Level in Italy and Spain: enhanced productivity and/or better preservation?

Landslide susceptibility analyses in flysch areas in the north-eastern part of the Adriatic coast

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