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Föllmi, Karl B.

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Föllmi, Karl B.
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Ancien.ne collaborateur.trice
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https://libra.unine.ch/handle/123456789/34296
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0000-0003-2641-8184

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  • Publication
    Accès libre
    Platform-induced clay-mineral fractionation along a northern Tethyan basin-platform transect: implications for the interpretation of Early Cretaceous climate change (Late Hauterivian-Early Aptian)
    (2008)
    Godet, Alexis
    ;
    Bodin, Stéphane
    ;
    Adatte, Thierry 
    ;
    Föllmi, Karl B. 
    High-resolution clay-mineral analyses were performed on upper Hauterivian to lower Aptian sediments along a platform-to-basin transect through the northern Tethyan margin from the Neuchâtel area (Switzerland), to the Vocontian Trough (France) in order to investigate links between climate change, carbonate platform evolution, and fractionation patterns in clay minerals during their transport.
    During the Hauterivian, the northern Tethyan carbonate platform developed in a heterozoan mode, and the associated ramp-like topography facilitated the export of detrital material into the adjacent basin, where clay-mineral assemblages are dominated by smectite and kaolinite is almost absent, thereby suggesting dry-seasonal conditions. During the Late Hauterivian Balearites balearis ammonite zone, a change to a more humid climate is documented by the appearance of kaolinite, which reaches up to 30% of the clay fraction in sediments in the Vocontian Trough. This prominent change just preceded the Faraoni Oceanic Anoxic Event and the onset of the demise of the Helvetic Carbonate Platform, which lasted to the late early Barremian.
    From the Late Barremian onwards, the renewed growth of the northern Tethyan carbonate platform in a photozoan mode and the associated development of a marginally confined platform topography fractionated the clay-mineral assemblages exported into hemipelagic settings: kaolinite particles were preferentially retained in proximal, platform settings, due to their size and their relatively high specific weight. In the inner platform environment preserved in the Swiss Jura, an average of 32% of kaolinite in the clay fraction is observed during the latest Barremian–earliest Aptian, whereas clay-mineral assemblages of coeval sediments from deeper depositional settings are dominated by smectite and show only minor amounts of kaolinite.
    This signifies that besides palaeoclimate conditions, the morphology and ecology of the carbonate platform had a significant effect on the distribution and composition of clay assemblages during the Late Hauterivian–Early Aptian along the northern Tethyan margin.
  • Publication
    Accès libre
    Demise of the northern Tethyan Urgonian carbonate platform and subsequent transition towards pelagic conditions: The sedimentary record of the Col de la Plaine Morte area, central Switzerland
    (2008)
    Föllmi, Karl B. 
    ;
    Gainon, François
    The sedimentary succession of the Col de la Plaine Morte area (Helvetic Alps, central Switzerland) documents the disappearance of the northern Tethyan Urgonian platform in unprecedented detail and suggests stepwise platform demise, with each drowning phase documented by erosion and phosphogenesis. The first identified drowning phase terminated Urgonian carbonate production in a predominantly photozoan mode. Using a correlation of the whole-rock δ13C record with the well-dated record from SE France, its age is inferred to as Middle Early Aptian (near the boundary between the weissi and deshayesi zones). A subsequent drowning phase is dated by ammonites and by a correlation of the whole-rock δ13C record as Late Early Aptian (late deshayesi to early furcata zone). A third drowning phase provides an ammonite-based age of Early Late Aptian (subnodosocostatum and melchioris zones) and is part of a widely recognized phase of sediment condensation and phosphogenesis, which is dated as latest Early to Middle Late Aptian (late furcata zone to near the boundary of the melchioris and nolani zones). The fourth and final drowning phase started in the latest Aptian (jacobi zone) as is also indicated by ammonite findings at the Col de la Plaine Morte. The phases of renewed platform-carbonate production intervening between the drowning phases were all in a heterozoan mode.
    During the ultimate drowning phase, phosphogenesis continued until the Early Middle Albian, whereas condensation processes lasted until the Middle Turonian. Coverage of the external margin of the drowned Urgonian platform by a drape of pelagic carbonates started only in the Late Turonian. During the Santonian, the external part of the drowned platform underwent normal faulting and saw the re-exposure of already lithified Urgonian carbonates at the seafloor.
    Based on the here-inferred ages, the first drowning phase just precedes oceanic anoxic episode 1a (OAE 1a or “selli event”) in time, and the second drowning phase partly overlaps with OAE 1a. The onset of the third drowning event slightly predates two further periods of increased organic-matter accumulation in the Vocontian Basin (Noir and Fallot levels), and the onset of the fourth and final drowning phase may coincide with two further periods of increased organic-matter accumulation in the Vocontian Basin (Jacob and Kilian levels, part of OAE 1b). These correlations indicate a relationship between the so-called anoxic episodes and the stepwise demise of the Urgonian platform, even if the onset of environmental change is registered earlier on the platform than in basinal sediments.
  • Publication
    Accès libre
    Carbon cycle perturbation and stabilization in the wake of the Triassic-Jurassic boundary mass-extinction event
    (2008)
    van de Schootbrugge, B.
    ;
    Payne, J. L.
    ;
    Tomasovych, A.
    ;
    Pross, J.
    ;
    Fiebig, J.
    ;
    Benbrahim, M.
    ;
    Föllmi, Karl B. 
    ;
    Quan, T. M.
    The Triassic-Jurassic boundary mass-extinction event (T-J; 199.6 Ma) is associated with major perturbations in the carbon cycle recorded in stable carbon isotopes. Two rapid negative isotope excursions in bulk organic carbon (δ 13Corg) occur within the immediate boundary interval at multiple locations and have been linked to the outgassing of 12C-enriched CO2 from the Central Atlantic Magmatic Province. In British Columbia, a positive δ 13Corg excursion of +5‰ (Vienna Peedee belemnite (V-PDB)) spans part or all of the subsequent Hettangian stage. Here, we examine the significance of these carbon isotope excursions as records of global carbon cycle dynamics across the T-J boundary and test the link between carbon cycle perturbation-stabilization and biotic extinction-recovery patterns. A combination of δ 13Corg and palynological analyses from the Late Triassic to Early Jurassic in the Mingolsheim core (Germany) suggests that organic carbon isotope variations are best explained as the result of both compositional changes in terrestrial versus marine input and disturbance and recovery patterns of major terrestrial plant groups across the T-J boundary. A new high-resolution δ 13Ccarb record from the Val Adrara section in the Southern Alps (Italy) spanning from the uppermost Rhaetian through Lower Sinemurian does not exhibit a negative excursion at the T-J boundary but does record a large positive δ 13Ccarb excursion of +4‰ (V-PDB) in bulk carbonate that begins at the T-J boundary and reaches a local maximum at the Early Late Hettangian boundary. Values then gradually decrease reaching +0.5‰ at the Hettangian-Sinemurian boundary and remain relatively constant into the Early Sinemurian. Complementary δ 13Ccarb data from 4 more sections that span the Hettangian-Sinemurian boundary support carbon cycle stabilization within the Upper Hettangian. Our analyses suggest that isotope changes in organic carbon reservoirs do not necessarily require a shift in the global exogenic carbon reservoir and that the positive excursion in the carbonate carbon isotope record is best explained as the combined result of an increase in atmospheric pCO2 leading to accelerated carbon cycling, decreased skeletal carbonate production, and increased organic carbon burial lasting several hundred thousand years. The termination of the positive inorganic carbon isotope excursion coincides with the recovery of marine skeletal carbonate producers and coeval changes in terrestrial vegetation and reflects the gradual reduction in pCO2 and the stabilization of the global carbon cycle during the Sinemurian.
  • Publication
    Accès libre
    Organic carbon deposition and phosphorus accumulation during Oceanic Anoxic Event 2 in Tarfaya, Morocco
    (2008)
    Mort, Haydon P.
    ;
    Adatte, Thierry 
    ;
    Keller, Gerta
    ;
    Bartels, David
    ;
    Föllmi, Karl B. 
    ;
    Steinmann, Philipp
    ;
    Berner, Zsolt
    ;
    Chellai, E.H.
    With 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 δ13Corg isotope excursion of +2.5‰ 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 ~ 2.5% to ~ 10%). This is interpreted as the consequence of a long-term 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 Preactive 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 Corg/Ptotal 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.
  • Publication
    Accès libre
    The Early Aptian Grünten Member : Description of a new lithostratigraphic unit of the helvetic Garschella Formation
    (2007)
    Linder, Pascal
    ;
    Gigandet, Johann
    ;
    Hüsser, Jean-Luc
    ;
    Gainon, François
    ;
    Föllmi, Karl B. 
    Aus einer relativ kleinen Anzahl von Aufschlussgebieten quer durch den distalen Teil der Helvetischen Zone der Schweiz, Österreichs und Deutschlands sind frühaptische Sedimente, zumeist unter dem Namen “obere Orbitolinenschichten" bekannt. Diese Sedimente werden hier, unter dem Namen Grünten-Member, formell als neues basales Member der Garschella-Formation definiert. Äquivalente und korrelierbare Sedimente existieren auch in der Vercors-Region der französischen Zone Dauphinoise. Das historische Typusprofil (Holostratotyp) des Grünten-Members liegt auf dem Grünten-Gipfel in Süddeutschland. Ein neues Typusprofil (Lectostratotyp) für das Grünten-Member wird in der besser geeigneten Bauen-Brisen Region der Zentralschweiz gewählt und ein zusätzliches Referenzprofil (Hypostratotyp) wird nahe des Rawilpasses im Berner Oberland der Schweiz definiert. In relativ proximalen Situationen überlagert das Grünten-Member frühaptische Kalke der Schrattenkalk-Plattform (Schrattenkalk-Formation), ihren Niedergang und ihr frühes “Ertrinken" dokumentierend. In relativ distalen Positionen überlagert es die gleichaltrigen hemipelagischen Sedimente der Drusberg- und der Mittagspitz- Formation. In vollständigen Abfolgen wird das Grünten-Member seinerseits durch die basale, phosphoritische Luitere-Schicht des Brisi-Members (Garschella- Formation) überlagert, welche das weitere “Ertrinken" der Schrattenkalk- Plattform im späten Aptian dokumentiert. Das Grünten-Member besteht im Wesentlichen aus einer einzigen stratigraphischen Sequenz, beginnend mit einer mergligen Basis und allmählich übergehend in einen oberen Teil aus Crinoiden-Bryozoen-Kalk. Seltene Ammoniten-Funde sowie sequenzstratigraphische Korrelationen deuten auf ein spät-frühaptisches Alter (Teile der Deshayesi-und Furcata-Ammonitenzonen). Im relativ proximalen Referenzprofil von Rawil enthült das Grünten-Member zwei Phosphorithorizonte. Phosphatreiche Horizonte sind auch von anderen proximalen Aufschlüssen des Grünten-Members bekannt., Early Aptian sediments mostly referred to as “upper Orbitolina beds" are known from a relatively small number of outcrop areas throughout the distal part of the Helvetic Zone of Switzerland, Austria and Germany. These sediments are here formally defined as a new, basal member of the Garschella Formation; the Grünten Member. Equivalent and correlatable sediments also exist in the Vercors region of the French Dauphinée Zone. The historical type section (holostratotype) of the Grünten Member is situated on the Grünten Mountain in southern Germany. A new type section (lectostratotype) for the Grünten Member is chosen in the better suited Bauen-Brisen area of Central Switzerland and an additional reference section (hypostratotype) is defined near the Rawil Pass in the Bernese Oberland of Switzerland. In relatively proximal settings, the Grünten Member overlies Early Aptian limestones of the Urgonian Carbonate Platform (Schrattenkalk Formation), documenting its demise and early “drowning". In relatively distal settings, it overlies the contemporary hemipelagic sediments of the Drusberg and Mittagspitz Formations. In complete successions, the Grünten Member is in turn overlain by the basal, phosphoritic Luitere Bed of the Brisi Member (Garschella Formation) documenting the continuing “drowning" of the Urgonian Carbonate Platform in the Late Aptian. The Grünten Member essentially consists of a single stratigraphic sequence, beginning with a marly base and gradually passing to crinoidal limestones at its top. Rare ammonite finds as well as sequence stratigraphic correlations suggest a late Early Aptian age (parts of the Deshayesi and Furcata Ammonite Zones). In the relatively proximal reference section of Rawil, the Grünten Member contains two phosphoritic horizons. Phosphateenriched horizons are also known from other proximal sections of the Grünten Member.
  • Publication
    Accès libre
    The Cenomanian/Turonian anoxic event at the Bonarelli Level in Italy and Spain: enhanced productivity and/or better preservation?
    (2007)
    Mort, Haydon
    ;
    Jacquat, Olivier
    ;
    Adatte, Thierry 
    ;
    Steinmann, Philip
    ;
    Föllmi, Karl B. 
    ;
    Matera, Virginie
    ;
    Berner, Zsolt
    ;
    Stüben, Doris
    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 δ13C 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 δ13C 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 δ13C 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 δ13C 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.
  • Publication
    Accès libre
    Enrichment of redox-sensitive trace metals (U, V, Mo, As) associated with the late Hauterivian Faraoni oceanic anoxic event
    (2007)
    Bodin, Stéphane
    ;
    Godet, Alexis
    ;
    Matera, Virginie
    ;
    Steinmann, Philipp
    ;
    Vermeulen, Jean
    ;
    Gardin, Silvia
    ;
    Adatte, Thierry 
    ;
    Coccioni, Rodolfo
    ;
    Föllmi, Karl B. 
    The Faraoni Level is a short-lived oxygen-deficient event that took place during the latest Hauterivian. In order to improve our understanding of the palaeoenvironmental conditions that occurred during this event, we have analysed the contents of several redox-sensitive trace elements (U, V, Mo, As, Co, Cd, Cu, Zn, Ni, Pb, Cr) from bulk limestone samples of late Hauterivian–early Barremian age from three reference sections. U, V, Mo and As show consistent and significant enrichments during the Faraoni event whereas the other redox-sensitive trace elements analysed here are not systematically enriched. In order to explain this discrepant behaviour, we propose that the Faraoni Level was deposited during a period of anoxic conditions near the sediment–water interface. The distinctive peaks in U, V, Mo and As contents are traceable throughout the three studied sections and represent a good correlation tool which helps to identify the Faraoni Level and its equivalents in the western Tethyan realm and outside of the Tethys. For example, a peak in U contents in upper Hauterivian sediments of the northwestern Pacific realm (ODP leg 185, site 1149) may well be an expression of the Faraoni event in this particular basin.
  • Publication
    Accès libre
    Phosphorus and the roles of productivity and nutrient recycling during oceanic anoxic event 2
    (2007)
    Mort, Haydon P.
    ;
    Adatte, Thierry 
    ;
    Föllmi, Karl B. 
    ;
    Keller, Gerta
    ;
    Steinmann, Philipp
    ;
    Matera, Virginie
    ;
    Berner, Zsolt
    ;
    Stüben, Doris
    Four sections documenting the impact of the late Cenomanian oceanic anoxic event (OAE 2) were studied in basins with different paleoenvironmental regimes. Accumulation rates of phosphorus (P) bound to iron, organic matter, and authigenic phosphate are shown to rise and arrive at a distinct maximum at the onset of OAE 2, with an associated increase in δ13C values. Accumulation rates of P return to pre-excursion values in the interval where the δ13C record reaches its first maximum. An offset in time between the maximum in P accumulation and peaks in organic carbon burial, hydrogen indices, and Corg/Preact molar ratios is explained by the evolution of OAE 2 in the following steps. (1) An increase in productivity increased the flux of organic matter and P into the sediments; the preservation of organic matter was low and its oxidation released P, which was predominantly mineralized. (2) Enhanced productivity and oxidation of organic matter created dysoxic bottom waters; the preservation potential for organic matter increased, whereas the sediment retention potential for P decreased. (3) The latter effect sustained high primary productivity, which led to an increase in the abundance of free oxygen in the ocean and atmosphere system. After the sequestration of CO2 in the form of black shales, this oxygen helped push the ocean back into equilibrium, terminating black shale deposition and removing bioavailable P from the water column.
  • Publication
    Accès libre
    Soil phosphorus uptake by continuously cropped Lupinus albus: A new microcosm design
    (2006-12-12)
    Le Bayon, Renée-Claire 
    ;
    Weisskopf, Laure
    ;
    Martinoia, Enrico
    ;
    Jansa, J
    ;
    Frossard, Emmanue
    ;
    Keller, F
    ;
    Föllmi, Karl B. 
    ;
    Gobat, Jean-Michel 
    When grown in soils with sparingly available phosphorus (P), white lupin (Lupinus albus L.) forms special root structures, called cluster roots, which secrete large amounts of organic acids and concomitantly acidify the rhizosphere. Many studies dealing with the understanding of this P acquisition strategy have been performed in short time experiments either in hydroponic cultures or in small microcosm designs with sand or sand:soil mixtures. In the present study, we applied an experimental design which came nearer to the natural field conditions: we performed a one-year experiment on large microcosms containing 7 kg of soil and allowing separation of rhizosphere soil and bulk soil. We planted six successive generations of lupins and analysed P uptake, organic P desorption, phosphatase activities and organic acid concentrations in different soil samples along a spatio-temporal gradient. We compared the rhizosphere soil samples of cluster (RSC) and non-cluster roots (RSNC) as well as the bulk soil (BS) samples. A total shoot biomass of 55.69 +/- 1.51 g (d.w.) y(-1) was produced and P uptake reached 220.59 +/- 5.99 mg y(-1). More P was desorbed from RSC than from RSNC or BS (P < 0.05). RSC and RSNC showed a higher activity of acid and alkaline phosphatases than BS samples and a higher acid phosphatase activity was observed in RSC than in RSNC throughout the one-year experiment. Fumarate was the most abundant organic acid in all rhizosphere soil samples. Citrate was only present in detectable amounts in RSC while malate and fumarate were recovered from both RSC and RSNC. Almost no organic acids could be detected in the BS samples. Our results demonstrated that over a one-year cultivation period in the absence of an external P supply, white lupin was able to acquire phosphate from the soil and that the processes leading to this P uptake took place preferentially in the rhizosphere of cluster roots.