Papers by Laurent Riquier
Volcanically Initiated Shoaling of the Marine Calcite Compensation Depth during Oceanic Anoxic Event 2 ( 94 Ma)
AGU Fall Meeting Abstracts, Dec 1, 2019
Gondwana Research, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Rock magnetism, sedimentology, gamma-ray logging, clay mineralogy and geochemistry at the Frasnian-Famennian GSSP (Coumiac, Montagne Noire, France): a synthesis
Data for: Nitrogen and carbon cycle perturbations through the Cenomanian-Turonian Oceanic Anoxic Event 2 (~94 Ma) in the Vocontian Basin (SE France)
Petrophysical Property Modifications by Alteration in a Volcanic Sequence at IODP Site U1513, Naturaliste Plateau
Journal of Geophysical Research: Solid Earth
Petrophysical properties of volcanic rocks are controlled by lithology and subsequent modificatio... more Petrophysical properties of volcanic rocks are controlled by lithology and subsequent modification by alteration processes. Investigating the linkages, using a range of different techniques, are important to establish how petrophysical properties can inform about the alteration state of volcanic rocks. Here, we compile petrophysical data and correlate these with geochemical and mineralogical analyses acquired from a volcanic sequence on the Naturaliste Plateau, offshore southwest Australia (IODP Site U1513). The sequence consists of alternating basalt lava flows and volcaniclastic deposits, intruded by multiple dolerite dikes. Variable alteration intensities from fresh-slight to strong are quantified using Chemical Index of Alteration. Intervals of slightly altered dikes exhibit low porosity and high values of bulk density, P-wave velocity and thermal conductivity. The increase of alteration intensity corresponds to decreases in bulk density to ∼2 g/cm3, P-wave velocity to ∼2000 m/s, thermal conductivity to ∼1.2 W/(m·K) and an increase in porosity up to 50%. Natural Gamma Ray and magnetic susceptibility vary downhole with rock composition and at lithologic boundaries. The distinct variations exhibit a good correlation with primary lithologic characteristics and secondary mineralogical and textural changes attributed to alteration processes. We provide synthesis models of petrophysical variation with alteration intensity. Although differences in primary lithology and alteration type introduce limitations and uncertainties, there is a reasonable applicability of our results to rapidly characterize the alteration intensity and volcanic stratigraphy in volcanic sequences and to calibrate wireline log-based determinations. This will help others to develop strategies for exploration, drilling, and geophysical research of volcanic rocks.
Geology
Trace metal elements (TMEs) are commonly used to reconstruct the environmental conditions present... more Trace metal elements (TMEs) are commonly used to reconstruct the environmental conditions present during the deposition of organic-rich sediments. For example, TME concentrations controlled by changes in primary productivity and redox conditions are widely used in paleoenvironmental studies. Recently, these proxies have undergone a resurgence of interest and are commonly used in large-scale (10–1000 km) studies. However, applying these geochemical proxies at basin scale while ignoring variations in sedimentation rates (SR) may lead to misinterpretation of paleoenvironmental conditions. Here, we show how SR can affect the geochemical records and may lead to incorrect interpretations of TME evolution. Accounting for SR, we computed the authigenic fraction accumulation rates of key TMEs in the Upper Montney Formation and Doig Phosphate (Triassic, western Canada), and we correct the concentration of these elements in the Vaca-Muerta Formation (Jurassic–Cretaceous, Argentina). Our SR-cor...
Formation of microbial organic carbonates during the late Jurassic from the Northern Tethys (Amu Darya Basin, Uzbekistan): Implications for Jurassic anoxic events
Global and Planetary Change
Abstract The Late Jurassic was a period of major global carbon cycle perturbations with episodes ... more Abstract The Late Jurassic was a period of major global carbon cycle perturbations with episodes of anoxia leading to regional accumulation of organic matter in sediments worldwide. The Tubiegatan section (SW Gissar Mountains, Uzbekistan) located in the Northern Tethys, shows atypical organic-rich limestone and marl deposits (up to 6% of total organic carbon) marked by pronounced negative excursions of δ13Ccarb (amplitude of ca. 12‰) and δ13Corg (amplitude of ca. 4‰) recorded during the Middle Oxfordian (Transversarium Zone). A transdisciplinary approach including sedimentology, palynofacies characterization, mineralogy, organic and inorganic geochemistry was carried out to elucidate the origin of these organic-rich deposits. Highest TOC are measured in nodular limestones, and lowest δ13Ccarb values in thinly laminated facies consisting in alternances of infra-millimeter-thick organic and carbonate laminae. In the latter, the presence of organic-carbonate peloids and of possible remnants of exopolymeric substances associated with clay indicate that these structures are probably mineralized laminated benthic microbial mats (i.e., stromatolites). Rock-Eval pyrolysis coupled to palynofacies analyses point to a dominant altered marine organic matter of probable algal/microbial origin, with subordinate continental phytoclasts inputs in the upper part of the organic-rich interval. Trace elements (U/Th, V/Cr and Mo/Al ratios) indicate two anoxic episodes coinciding with the highest TOC, punctuated by dysoxic periods. Such O2-depleted conditions have allowed the preservation and probably the development of anaerobic microbial communities in the microbial mats. In these latter, sulfate reduction probably had a significant contribution to the production of carbonates, which would explain the precipitation of pyrite and the relatively low δ13Ccarb values. The progressive decrease then disappearance of kaolinite from the base of the organic-rich interval, is interpreted as a progressive aridification of the Amu Darya Basin during the Transversarium Zone, culminating with the progradation of a large-scale gypsum sabkha overlying the organic deposits. Overall, the organic-rich deposits could record the onset of the disconnection of the Amu Darya Basin from the open sea to the south, induced by compression and subsequent uplifts in the Afghan and Central Iranian blocks. The elevated evaporation, coupled with the presence of hydrological barriers (such as coral reefs) could have led to the formation of local to regional anoxic conditions in the Amu Darya Basin. Similar microbial organic accumulations are recently known throughout the Tethys (e.g., Arabian Plate, Western Europe) and from other oceans (e.g., Central Atlantic, Pacific) during the Late Jurassic, suggesting common controlling factors. The increase of organic matter storage worldwide coupled with potential methane release could have in turn induced major perturbations of the carbon cycle during the Oxfordian-Kimmeridgian interval. The relatively shallow anoxia model proposed in this study contrasts with the well-known organic carbon-rich pelagic models proposed for the Jurassic anoxia (e.g., Toarcian, Kimmeridgian) and Cretaceous OAEs.
International Journal of Coal Geology
This study focuses on the thermal maturity assessment of Silurian-Devonian sediments from the Gha... more This study focuses on the thermal maturity assessment of Silurian-Devonian sediments from the Ghadamis Basin, North Africa, comparing optical and geochemical analyses of palynomorphs. In southern Tunisia, the investigated subsurface cored section comprises the Argiles Principales Formation of Silurian age. In Libya, the succession studied covers the Awaynat Wanin III and IV formations, assigned to the Late Devonian (Frasnian-Famennian). Geochemical approaches used to reconstruct thermal alteration of sediments necessitate advanced, relatively expensive analytical techniques. In this study, the effectiveness of the less costly, relatively simple approaches of visually assessing palynomorph colour to determine thermal alteration (i.e., SCI: Spore Colour Index, TAI: Thermal Alteration Index and PDI: Palynomorph Darkness Index) was evaluated. SCI and TAI are qualitative methods, strictly related to the operator's perception, which use ten and five point scales respectively, to characterize colour in terms of illustrated specimens and/or descriptions. In contrast, PDI is obtained from the measurement of the red, green and blue (RGB) intensities of light transmitted through palynomorphs, using standard optical microscopes and digital cameras. The palynomorph-based thermal alteration estimates were compared to Rock-Eval pyrolysis data from the same samples. This calibration showed a linear relationship between these quantitative parameters and PDI. These results show that PDI is more reliable than the SCI and TAI methods.
Perturbations des environnements marins, à la limite Frasnien-Famennien (Devonien Terminal) : apport de la géochimie inorganique et du magnétisme des roches
Http Www Theses Fr, 2005
Magnetization carriers of grey to red deep-water limestones in the GSSP of the Givetian-Frasnian boundary (Puech de la Suque, France): signals influenced by moderate diagenetic overprinting
Geological Society, London, Special Publications, 2015
Limestones at the Puech de la Suque Global Boundary Stratotype Section and Point (GSSP) of the Gi... more Limestones at the Puech de la Suque Global Boundary Stratotype Section and Point (GSSP) of the Givetian–Frasnian boundary show a drastic change towards much higher magnetic susceptibility values in the Givetian rocks. Different rock magnetic parameters indicate that ferromagnetic minerals are the main controlling factor. The ferromagnetic fraction is composed of low- (magnetite-type) and high-coercivity (hematite and goethite) phases. Confirmed by the spectral reflectance, high coercivity minerals are fluctuating along the section with a higher abundance in the basal Frasnian. These phases may be of secondary origin and produced during burial stage. The magnetite-type phase contains two different grain-size populations. The identified that Stable Single-domain/Superparamagnetic (SSD/SP) particles are of diagenetic origin and their amount decreases slightly upwards. A second group of magnetite grains correspond to coarse-grained particles identified using the squareness v. coercive f...
Evidences for an orogenic-induced global cooling at the Frasnian-Famennian boundary (ca 376 Ma BP)
Late Devonian time (Famennian, 376--362 Ma BP) is a period of both intense orogenic activity and ... more Late Devonian time (Famennian, 376--362 Ma BP) is a period of both intense orogenic activity and drastic climatic variations with the onset of a major glaciation event upon parts of the Gondwanian Southern America and Africa situated in high southern latitudes. This global cooling event is coeval with a significant fall in the atmospheric CO_2 content as suggested both by
To provide a new insight into the diagenetic versus detrital origin of the magnetic susceptibilit... more To provide a new insight into the diagenetic versus detrital origin of the magnetic susceptibility variations in ancient carbonate sequences, a study was conducted within four Frasnian-Famennian platform carbonate sections from Germany, France and Morocco. The study includes along-section magnetic susceptibility and carbonate content measurements complemented by analyses of magnetic hysteresis parameters, inorganic geochemistry and clay mineralogy. Our results show that the magnetic susceptibility evolution is dominantly controlled by the variations in the concentration of low-coercivity ferromagnetic magnetite grains and, to a lesser extent, of paramagnetic clays. In more detail, hysteresis ratios suggest the coexistence of two magnetite populations with significantly different grain size: (1) a dominantly coarsegrained detrital fraction including a mixture of multidomain and single-domain particles (2) an authigenic fine-grained fraction composed of a mixture of single-domain and superparamagnetic particles. Despite a diagenetic imprint on the clay assemblages, no relationship is established between magnetic susceptibility and illite crystallinity, therefore discarding a noticeable distortion of primary within-section magnetic susceptibility evolution. The overall inherited character of the magnetic susceptibility fluctuations is corroborated by a significant correlation of magnetic susceptibility with terrigenous proxies (Zr, Th). The poorer correlation of magnetic susceptibility with the Fe content is consistent with the existence of a very fine-grained authigenic magnetite component that possibly induces a global magnetic susceptibility increase at the section scale, but no distortion of the within-section evolution. The magnetic susceptibility curves presented here provide a general record of climate-driven detrital influx and carbonate productivity through Frasnian-Lower Famennian times.
Mountain building-enhanced continental weathering and organic carbon burial as major causes for climatic cooling at the Frasnian-Famennian boundary (c. 376 Ma)?
Terra Nova, 2005
... Averbuch, O., Tribovillard, N., Devleeschouwer, X., Riquier, L., Mistiaen, B. and Van Vliet-L... more ... Averbuch, O., Tribovillard, N., Devleeschouwer, X., Riquier, L., Mistiaen, B. and Van Vliet-Lanoe, B. (2005), Mountain building-enhanced ... of atmospheric CO 2 content (and the associated greenhouse effect) by increased silicate weathering (eg Raymo, 1991; François et al., 1993 ...
Transfer of germanium to marine sediments: Insights from its accumulation in radiolarites and authigenic capture under reducing conditions. Some examples through geological ages
Chemical Geology, 2011
In the geosphere, germanium (Ge) has a chemical behavior close to that of silicon (Si), and Ge co... more In the geosphere, germanium (Ge) has a chemical behavior close to that of silicon (Si), and Ge commonly substitutes for Si (in small proportions) in silicates. Studying the evolution of the respective proportions of Ge and Si through time allows us to better constrain the ...
Chemical Geology, 2006
In the Harz Mountains (Germany), three Late Devonian sections, Aeketal, Hühnertal and Kellwassert... more In the Harz Mountains (Germany), three Late Devonian sections, Aeketal, Hühnertal and Kellwassertal, were analyzed for major-and trace-element concentration. The inorganic geochemical data were used to determine the environmental conditions, associated with the deposition of the two Late Frasnian black Kellwasser horizons in a submarine-rise environment. Low Ti/Al and Zr/Al values and slight enrichment in nutrient-and organic matter-related trace elements (e.g., Ba, Cu, and Ni) suggest that the Kellwasser horizons were deposited during two periods of minimum detrital input but relatively elevated primary production. Enrichments in U, V, and Mo in both black Kellwasser horizons and values of redox indices, including U/Th, V/Cr, and Ni/Co, indicate oxygen-restricted conditions prevailed during the Late Frasnian times. Under oxygen-depleted conditions, reductive diagenesis caused precipitation of iron sulphides, such as pyrite, that are observed with SEM. However, variations in major and trace element concentrations are not similar in the two Kellwasser horizons, particularly regarding redox markers. The Lower Kellwasser horizon seems to be more O 2 -depleted than the Upper Kellwasser horizon in some German sections. On the basis of these results, we propose that the two Kellwasser horizons are not caused by identical conditions. The Lower Kellwasser horizon results from increased primary productivity, enhanced by land-derived nutrient-loading and which triggered the anoxic conditions recorded in drowned platform setting. In contrast, the Upper Kellwasser horizon results from the onset of oxygen-impoverished bottom water in the deepest part of the ocean, due to episodic water stratification during maximum Frasnian flooding. Oxygen-depleted water may have impinged shallower environment during the linguiformis transgressive pulse. Nutrients would have been released from organic matter decay under reducing conditions and brought up to the photic zone during episodic water mixing.
Chapter 8Productivity and bottom water redox conditions at the Frasnian-Famennian boundary on both sides of the Eovariscan Belt: constraints from trace-element geochemistry
Developments in Palaeontology and Stratigraphy, 2005
ABSTRACT The Late Devonian Frasnian-Famennian (F-F) mass extinction event coincides in many place... more ABSTRACT The Late Devonian Frasnian-Famennian (F-F) mass extinction event coincides in many places with the depositionof Corg-rich “Kellwasser” facies. Four F-F boundary sections representative of platform and basin environments from widely separated locations (Morocco, Germany, and France) were analysed for inorganic geochemistry, especially trace elements (redox and productivity proxies), in order to describe paleodepositional environments for the Kellwasser horizons. Ni/Co, V/Cr, U/Th, and V/(V+Ni) ratios, as well as redox trace metal concentrations indicate that oxygen-depleted conditions existed during the times of Kellwasser facies deposition. In platform settings, dysoxic conditions seem to be limited to the Late Frasnian. In basinal settings, oxygen depletion was stronger and persisted into the Early Famennian. Enrichments of Ba, Cu, Ni, that are limited to the Late Frasnian, show that surface productivity was relatively high and organic matter could accumulate, especially in the deeper environments. The stratigraphical distribution of several geochemical markers are linked with two positive excursions of the δ13Ccarb signal that result from enhanced organic matter burial. Reducing conditions likely resulted from high productivity of Late Devonian marine ecosystems. Intense nutrient supply resulted probably from the biogeochemical recycling of nutrients, and/or runoff from emerged lands. Coupled with other factors, such as rapid sea-level fluctuations and climatic changes, oxygen-depleted conditions and eutrophication would have modified Late Devonian environments and could be possible factors in the F-F mass mortality.
The Plenus Cold Event Record in the Abyssal DSDP Site 367 (Cape Verde, Central Atlantic): Environmental Perturbations and Impacts on the Nitrogen Cycle
The Oceanic Anoxic Event 2, at the Cenomanian-Turonian boundary (∼93.9 Ma), was an episode of wid... more The Oceanic Anoxic Event 2, at the Cenomanian-Turonian boundary (∼93.9 Ma), was an episode of widespread burial of organic matter in marine sediments, underlined by a positive carbon-isotope (δ13C) excursion observed worldwide. Within this episode of O2-depleted conditions, a short interval of cooling, termed as the Plenus Cold Event, has been recorded in many sites and sections in the northern hemisphere (Tethyan domain, Western Interior Seaway, proto-North Atlantic Ocean). But, its record and its impact on the biogeochemical cycles of carbon and nitrogen in the southern part of Central Atlantic Ocean has not been explored yet. Here, we present a detailed geochemical study of the Deep Sea Drilling Project site 367 (Cape Verde) based on a compilation of previous and new data of carbon and nitrogen isotope signals as well as trace element concentrations. The aim of this study is to better constrain the evolution of oxygenation in the water column and the associated changes in nitroge...
The tectonic and paleoceanographic setting of the Great Australian Bight (GAB) and the Mentelle B... more The tectonic and paleoceanographic setting of the Great Australian Bight (GAB) and the Mentelle Basin (MB; adjacent to Naturaliste Plateau) offered an outstanding opportunity to investigate Cretaceous and Cenozoic climate change and ocean dynamics during the last phase of breakup among remnant Gondwana continents. Sediment recovered from sites in both regions during International Ocean Discovery Program Expedition 369 will provide a new perspective on Earth’s temperature variation at sub-polar latitudes (60°–62°S) across the extremes of the mid-Cretaceous hot greenhouse climate and the cooling that followed.
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Papers by Laurent Riquier