Marty, D. & Meyer, Ch.A. 2006 Depositional conditions of carbonate-dominated palustrine sedimentation around the K-T boundary (Faciès Rognacien, northeastern Pyrenean foreland, southwestern France) (original) (raw)
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2001
The Faciès Rognacien is a sequence of highly bioturbated and pedogenically modifi ed palustrine carbonates that were deposited under oxic conditions around the Cretaceous-Tertiary (K-T) boundary in the northeastern Pyrenean foreland basin (SW France). The sedimentary structures and early diagenetic features identifi ed (mottling, nodule formation, brecciation, pseudomicrokarst, cracking, charophytes, Microcodium) suggest deposition in a palustrine environment between the subarid and intermediate climate type. Sedimentological and paleoecological analysis enables us to distinguish two facies associations, the lacustrine pond facies and the freshwater marsh facies associations. The majority of the carbonates are attributed to the freshwater marsh facies. The lacustrine pond facies occurs only in isolated paleolows, and is identifi ed on the basis of its paleobiological content (charophytes, ostracodes). This suggests that the palustrine carbonates of the Faciès Rognacien were deposited in a seasonal wetland (carbonate-producing freshwater marsh), rather than in the marginal zone of a large, shallow lake. In this wetland paleoenvironment, all carbonates underwent widespread pedogenesis, and small, ephemeral ponds are of limited distribution, most likely recording deposition in paleolows.
Sedimentary Geology, 2024
An integrated approach combining petrography, photogrammetry, geochronology, SEM, and geochemical data was utilized to analyze lithofacies, stacking patterns, lateral facies variations, and interpret environmental dynamics during the deposition of carbonates from “La Barre du Cengle” in the Early Paleogene. Located in the SE of France, the elliptical Cengle Plateau stretches 7 km from east to west and 2 km transversely, featuring cliffs ranging in thickness from 20 to 35 meters. These cliffs showcase grayish, beige, and pinkish limestones dominated by palustrine facies, forming part of the 'Calcaire de Saint Marc' Formation of the Arc Basin. Sedimentary deposits within this interval were repeatedly subjected to subaerial exposure due to fluctuations in lake levels driven by climate, resulting in the organization of elementary sequences at decimetric to metric scales, which stack up into small-scale sequences at the decametric order. Deposition occurred under climatic conditions ranging from subarid to subhumid, with paleogeographic variations in the basin corresponding to changes in lake base levels over time and space. At least four frequencies of base level variation are present: very high frequency and seasonal, generating very short-term subaerial exposures and transforming lacustrine facies into palustrine ones; high frequency resulting in short-term subaerial exposures and generating the surfaces that limit the elementary sequences; medium frequency leading to long-term subaerial exposures, resulting in the formation of pedogenic facies and features; and low frequency which corresponds to the deposition of the entire set of limestones that form the cliff. The transition between lacustrine, palustrine, and pedogenic environments consistently occurs from west to east over time. In the more distal regions, the proportion of lacustrine facies tends to increase, and the thicknesses of the preserved sedimentary record tend to be greater. Conversely, palustrine and pedogenic facies predominate in the more proximal areas, typically resulting in decreased thickness.
Sedimentary Geology
A 220-meters thick carbonate-dominated succession has been deposited in shallow-water, saline lake environments during the Lower to Middle Priabonian (MP17A-MP18 mammal zones) in the Saint-Chaptes Basin (south-east France). The palaeoenvironmental, paleoclimatic and palaeogeographic significance of such salt lake carbonates has been deciphered on the basis of a multi-proxy analyses including 1) depositional and diagenetic features, 2) biological components (molluscs, benthic foraminifera, characean gyrogonites, spores and pollens), 3) carbon and oxygen stable isotopes, 4) trace elements and 5) clay mineralogy. Five stages of lacustrine system evolution have been identified: 1) freshwater closed lake under dry climate (unit U1); 2) fresh to brackish water lacustrine deltaic system with a mixed carbonate-siliciclastic sedimentation under relatively wet climatic conditions (unit U2); 3) saltwater lacustrine carbonate system under humid climatic setting (unit U3); 4) evaporitic lake (unit U4); and 5) closed lake with shallow-water carbonate sedimentation under subtropical to Mediterranean climate with dry seasons (unit U5). Upper Eocene aridification is evidenced to have started as early as the earliest Priabonian (unit U1: MP17A mammal zone). A change from humid to dryer climatic conditions is recorded between units U3 and U4. The Lower-Mid Priabonian saline lake is interpreted as an athalassic (inland) lake that have been transiently connected with neighboring salt lakes influenced by seawater and/or fed with sulfates deriving from recycling of evaporites. Maximum of connection with neighboring salt-lakes (Mormoiron Basin, Camargue and Central grabens, Hérault Basin) likely occurred during unit U3 and at the base of unit U5. The most likely sources of salts of these adjacent basins are: 1) Triassic evaporites derived from salt-diapirs (Rhône valley) or from paleo-outcrops located east of the Durance fault or offshore in the Gulf of Lion; or 2) marine incursions from the south, through Paleogene grabens in the Gulf of Lion.
Palaeogeography, Palaeoclimatology, Palaeoecology, 2013
Biostratigraphic studies of Barremian platform carbonates from SE France, and nearby regions indicate the Last Occurrence (LO) horizons of some common shallow water taxa. Firstly two dasycladale algae: Piriferella paucicalcarea and Salpingoporella genevensis, which have their first occurrence in the upper Hauterivian disappear in the lower Barremian, at the Nicklesia pulchella-Kotetishvilia compressissima transition. Secondly a rudist bivalve: the genus Agriopleura, which has its first occurrence in the upper Hauterivian has its LO in the lower upper Barremian, within the Gerardhtia sartousiana zone. The specific stratigraphic levels of the above bioevents recorded in platform carbonates may be used for dating corresponding ammonite free-successions. Stratigraphic implications are constrained by the biogeographical extent of the key species which is essentially the Western and Central European margin of the Mediterranean Tethys. The joint LO of P. paucicalcarea and S. genevensis are inferred to have been linked with oceanographic and climatic changes, i.e. a cooling event. Platform carbonates were interrupted by a drowning event represented by a Maximum Flooding Surface or Transgressive surface. Shallow water Orbitolinidae record significant extinctions and deep water ammonites show a significant turnover. Similarly, modifications in ammonite faunas, bottom currents, temperature changes, i.e. cooling, and a major extinction among the family Orbitolinidae coincided with the LO of Agriopleura. Platform perturbations, including exposure, possibly a sequence boundary, and basin margin instability, both with a tectonic background, were associated with this event. The foregoing events and the linkage of palaeobiogeographic changes, that is the migration of the key taxa towards southern latitudes, in correspondence with the LO bioevents indicate that thermal changes, including seasonality, appear to have been the prominent controlling factor.
Cretaceous Research, 2011
In Provence and Languedoc, four drowning events were identified in platform carbonates of late Bar-remianeBedoulian age. Their recognition is based on sedimentological and stratigraphical evidence, and their timing, referred to ammonite zones or subzones, is as follows: (1) Late Barremian, at the G. sartousianaeImerites giraudi transition, or merely the lowermost part of the I. giraudi zone, (2) Middle Bedoulian, at the DeshayesitesweissieDeshayesites deshayesi transition, (3) Mid late Bedoulian in correspondence with the "Roloboceras hambrovi subzone", (4) Late Bedoulian at the Deshayesites grandiseDeshayesites furcata transition. Corresponding events are also well expressed in basinal settings where they are marked by significant facies and faunal changes. These four successive drowning events distinguish four successive steps in platform development and demise. Step 1 was coeval with the onset of the Bedoulian palaeogeography and started after drowning event (1) with a drastic reduction of shallow platform settings with rudists, usually replaced by Palorbitolina facies. The ensuing recovery of rudist facies and, following drowning event (2), subsequent step 2 marked the developmental phase of the platform system, whereas steps 3 and 4, each prefaced by a drowning event, were associated with its demise. Step 1 represents the major spreading phase of the Urgonian type facies spectrum including bioclastics, coral and rudist facies groups. In Provence, step 1 was characterized by a bipolar (N-S) progradation, and aggradation was coeval with a maximum of subsidence. The termination of step 1 was marked by the emergence of the antecedent platform margin. Step 2, which followed the disappearance of rudist facies and the extreme spatial reduction of both coral and bioclastic facies, started with the flooding of the antecedent platform and the development of Palorbitolina and cherty limestones. Shallow water bioclastics and/or coral facies recovered rapidly on top of the pre-existing emerged areas and developed locally as bioclastic shoals. Step 2 documents a regional reorganisation of subsidence patterns. The infralittoral (high illuminated environments) "Urgonian facies" are therefore essentially present in the Lower Bedoulian, and circalittoral (relatively deep low illuminated environments) deposits dominate in the Upper Bedoulian. This pattern, typical for SE France and wide parts of the Helvetic shelf, departs from that of adjacent regions (e.g. SW France, Spain) where late Bedoulian platform carbonates have a significant record. The record thus shows that the demise of the Urgonian platform was a step-wise phenomenon which cannot be ascribed to a single event, i.e. the Goguel/Selli OAE1a main event.
Palynofacies variations in a carbonate ramp system environment (Upper Muschelkalk, NE France)
Bulletin De La Societe Geologique De France, 2003
This study analyses variations in the size of black woody phytoclast and palynofacies types of shallow subtidal environments evolving to deeper subtidal environments, of latest Illyrdian-latest Fassanian age (Upper Muschelkalk). Some of the results display some discrepancies between elevated particle sizes that were supposedly deposited in a relative proximal source and the rich veryhachid palynofacies that are thought to represent distal marine environments. A case study of the succession in the Héming quarry, located in the Alsace-Lorraine trough (southwestern part of the intracratonic Germanic basin) reveals that : (1) the palynological assemblages are dominated by acritarchs belonging to micrhystridids, disaccate pollen and woody phytoclasts; (2) the abundance of phytoclasts, sporomorphs and marine groups is not correlated with lithologies; (3) the length of the processes of micrhystridids is not a useful parameter in defining palynofacies types. In carbonate ramp environments, many factors could have confused the palynological signals such as high-energy events and the water level on which the nutrient supply depended pro parte. All these factors seem to have been governed by climatic or tectono-eustatic events. Les variations des palynofaciès dans un système de rampe carbonatée du Muschelkalk supérieur du NE de la France.
Palynofacies and sea-level changes in the Upper Cretaceous of the Vocontian Basin, southeast France
Götz, A.E. & Feist-Burkhardt, S. 2008, 2008
Upper Cretaceous platform carbonates of the Vocontian Basin (southeastern France) have been investigated in a cross-section from the proximal deposits exposed in the lower Rhône Valley to the distal part of the basin in the Southern Subalpine Ranges north of Nice. The stratigraphic interval studied in detail spans the uppermost Turonian and Coniacian.Palynofacies patterns were used to detect eustatic signals at a third-order scale and are the tool for correlation of proximal and distal platform deposits. The organic constituents observed in the studied samples have been grouped into a continental fraction, including higher plant debris (phytoclasts) and sporomorphs, and a marine fraction with dinoflagellate cysts, acritarchs, prasinophytes, and foraminiferal test linings. The main factors influencing the stratigraphic and spatial distribution of land-derived, allochthonous, and marine, relatively autochthonous, organic particles are the proximity of land, the organic productivity, the degree of biodegradation and the hydrodynamic conditions of the depositional system. Palynofacies parameters used for the sequence stratigraphic interpretation are: (1) the ratio of continental to marine constituents (CONT/MAR ratio); (2) the ratio of opaque to translucent phytoclasts (OP/TR ratio); (3) the phytoclast particle size and shape; and (4) the relative proportion and species diversity of marine plankton. Ternary diagrams illustrating significant proximality changes were used to decipher transgressive-regressive trends within the succession.High amounts of translucent phytoclasts and decreasing values of the CONT/MAR ratio occur during the phase of relative sea-level rise in the upper Turonian. The stratigraphic interval of maximum flooding around the Turonian/Coniacian boundary is marked by the highest abundance and species diversity of dinoflagellate cysts, and by high percentages of opaque, equidimensional particles within the phytoclast group. The OP/TR ratio is still high within the lower Coniacian representing the early highstand deposits, whereas the relative abundance of marine constituents is again decreasing. Sedimentary organic matter of the upper Coniacian is dominated by large, blade-shaped, mainly opaque phytoclasts, which are a characteristic palynofacies signature of late highstand deposits.The present study demonstrates the high potential of palynofacies analysis in high-resolution stratigraphy and correlation of sedimentary series of shallow epeiric seas.
Holocene evolution of two ponds on the Devès Plateau in the French Massif Central
Diatom Research, 2012
The siliceous sub-fossil content (diatoms, chrysophyte cysts, sponges and phytoliths) of two cores was studied to determine the evolution and environmental changes that have occurred since the formation of two fenland lakes, Lac de Collanges and Lac de Freycenet, on the Devès Plateau, Massif Central, France. Cluster analyses determined eight siliceous zones, whereas a detrended correspondence analysis showed similar changes occurring in both sites, and principal component analysis identified four major shifts occurring over time at both sites, corresponding to the establishment of the fenland, the development of a pond and changes in the terrestrial environment. Four classic pollen zones previously determined for the French Massif Central were recorded in the core. The Boreal and beginning of the Old Atlantic period (9445–9250 cal bp) are marked by the development of the fenland, a decrease in pine trees and loss of grassland. The siliceous component was dominated by chrysophyte cysts indicating a cooler and lower trophic level. The Atlantic period (8365–7852 cal bp) saw maximum expansion of the fenland and the first occurrence and dominance of Aulacoseira perglabra (Østrup) Haworth, indicating higher water levels as a result of climate change. Increasing numbers of sponge spicules and the decrease in A. perglabra showed a shift to dryer conditions. During this phase, greater and more frequent droughts occurred in Collanges compared with Freycenet, most likely due to its smaller drainage basin. With the Subboreal, around 5000 cal bp, a change in conditions occurred: A. lacustris (Grunow) Krammer became the most important centric diatom and phytoliths became an important component. Pine trees increased and total herb and grasses became more important. The increase in total herb and grass pollen, along with the major increase in phytoliths, indicated an increase in human agro-pastoral activity within the area. The Subatlantic saw a decrease in water levels with periods of desiccation. A cyclic pattern of wet and dry phases was documented by a diatom increase in regularly moist and mostly moist subaerial environments. Including counts of phytoliths, sponges and chrysophyte cysts with diatoms allows better interpretation of the changes occurring over time within the area and permitted determination of the arrival of human agro-pastoral activity. The other three groups, namely phytoliths, sponges and cysts, were particularly useful when certain samples contained very few or were totally devoid of diatoms.
Sedimentary Geology, 2005
Cathodoluminescence petrography has been combined with bulk-rock and micro-sampled 87 Sr/ 86 Sr, y 18 O and y 13 C analyses to reconstruct the diagenetic history of Lower Cretaceous (Barremian) limestones exposed at the southern margin of the Vercors carbonate platform in southeastern France. Stratigraphic and geographic trends in these analyses, coupled with mass balance water-rock interaction modeling, have been used to constrain the chemical composition, source, and relative timing of the groundwaters responsible for diagenetic alteration. This study was completed on the Montagnette outcrop, which is composed of two stacked 70-m-thick units of prograding platform-margin limestones that interfinger with marly basinal sediments. The Montagnette exposure is exceptional, in that it is a single complete outcrop of basin-to-platform limestones that are preserved in their original lateral depositional continuity.
Sedimentary Geology, 2009
A detailed sedimentological, geochemical and mineralogical study is carried out on the Early Bajocian to Early Callovian (Middle Jurassic) limestones of the Paris Basin. Objectives are to document and explain the facies changes in the context of the climate/environmental evolution at the NW European scale. Deposits include 18 lithofacies which are stacked into 10 third-order depositional sequences. At a greater time scale, 4 biosedimentary packages are distinguished by their allochems associations. (1) An intracratonic carbonate environment with coral reefs and crinoid-rich facies is typical of the Early Bajocian. (2) A major facies change occurred at the Early/Late Bajocian transition with a shift from crinoid-and coral-rich facies to ooid-rich facies. During the Late Bajocian, a southward-dipping ooid ramp with successive progradational trends was emplaced.