The integrative analysis of a lacustrine carbonate succession from Butte Iouton hill (Vistrenque basin, SE France) brings new insights into depositional models and stacking patterns of oolitic saline ...lake margins and provides new details regarding the late Eocene paleogeography of southeast France. Depositional facies analysis and paleoenvironmental reconstructions allow reconstructing an oolitic lacustrine ramp model, displaying from the proximal to the distal areas: (1) shallow marginal saline lake domain with deposition of planar microbial laminites, and molluscan-ostracodal wackestone, (2) a more distal and open lacustrine environments with low to moderate energy characterized by the deposition of peloidal grainstones and (3) a domain of higher energy with accumulation of ooids mixed with peloids in the vicinity of the area of ooid production. Lake margin carbonate sedimentation dominantly occurred during stages of lake transgression while subaerial exposure surfaces developed during periods of negative inflow-evaporation balance (forced regression). Carbon and oxygen isotopes together with vertical trends in salinity inferred from molluscan associations show that lake transgression does not result from increasingly positive freshwater-evaporation balance volume but from the combination of subsidence and outflow from neighbouring saline waterbodies. The Butte Iouton carbonate margin is part of a set of interconnected saline lakes, occupying continental basins from Languedoc and Rhodanian region during the Priabonian, with a siliciclastic-dominated sedimentation in the southern margin, sourced by erosion of Pyrenean reliefs, and a carbonate-dominated northern margin with significant oolitic sedimentation in high-energy nearshore area.
The Upper Cretaceous sedimentary series of the Castilian marine ramp and continental basins (central northern Spain) have yielded numerous charophyte bearing sites which extend within the middle ...Cenomanian to upper Maastrichtian succession. The purpose of the paper is both to list the recognized charophyte taxa and to describe the sedimentary sequences in which the charophytes were found in order to reconstruct their depositional environments. The charophyte flora comprises 2 families, 15 genera and 28 species, including 3 new taxa: Lamprothamnium elongatum, Lamprothamnium ovoideum, Pseudoharrisichara sedanoensis. Among 27 charophyte bearing sites, 22 were formed during episodes of emersion and terrestrial conditions that interrupted the marine succession of the Castilian ramp, and 5 are from restricted Castilian continental basins that developed from the Campanian–Maastrichtian boundary onwards. The Campanian–Maastrichtian fossiliferous sites allow elucidating floristic and biostratigraphic correlations with the charophyte floras from Catalonia and from the Serrania de Cuenca.
•A Late Cretaceous charophyte rich flora from northern central Spain is described.•Three new species are reported: Lamprothamnium elongatum, L. ovoideum, Pseudoharrisichara sedanoensis.•Numerous depositional environments are reconstructed.•Accurate datations thanks to interbedding with fossiliferous shallow marine deposits are provided.
The northern boundary of the Central High Atlas was affected by a transgression during the Aptian that reached the junction zone between the Middle and the High Atlas. In this sector (Naour-Aghbala) ...which corresponds to the presumed closure zone of this Aptian Atlantic marine trough, the sedimentary record reveals a strong dependence on the regional structural framework. The Barremian continental sedimentation is concentrated in an elongated W-E highly subsiding zone, limited to the south by the polyphase Aghbala-Afourer Fault Zone (AAFZ), which corresponds to the contact between the main Atlasic Belt and its northern boundary (Beni Mellal Atlas). The Aptian deposits preserve similar littoral marine characters from West to East without showing any confined facies, which could evoke the eastern limit of the gulf. On the other hand, towards the North, the Aptian layers rapidly change from marine to lagoonal then to continental facies. The paleogeographic boundary of the Aptian shoreline, oriented E-W, is locally controlled by the North El Ksiba Fault (NKF) in the North. The Aptian Atlantic transgression, closely linked to the narrow Barremian graben, shows a wide northward extension of the marine sedimentary area.
The Barremian graben highlighted in the Aghbala-Naour area represents only a segment of a major east-west intracontinental rift that continued eastward with the more recent frontal thrust of the eastern Moroccan High Atlas. This faulted structure was the penetration axis of a double transgression: from the Tethys to the East and from the Atlantic Ocean to the West on the emerged Atlasic domain.
•Identification of an E-W intracontinental Barremian graben in the Aghbala-Naour area.•Evidence of an Aptian paleogeographic S–N zoning from marine to continental deposits.•Geodynamic evolution from Barremian intracontinental rift to Aptian marine gulf.•Extensional faulting between Atlantic & Tethyan Oceans, across the High Atlas domain.
Stratigraphic, sedimentologic, and micropaleontologic studies have been undertaken on the “Infra-Cenomanian” continental red beds (= Dekkar Group) located on the northern side of the Moroccan eastern ...High Atlas. Rich charophyte assemblages containing Sphaerochara magna, Ascidiella stellata, Hemiclavator sp. A, Globator trochiliscoides, Atopochara trivolvis, At. triquetra, and Flabellochara harrisii indicate a late Barremian age for the lower part of the series. Within the continental deposits we have discovered in the Middle Member of the Dekkar 2 Formation limestones and marls containing echinoderms, dasycladacean algae and foraminifera (miliolids, Ammobaculites sp., Choffatella decipiens). The existence of two littoral to lagoonal-marine intercalations within the continental sedimentation reveals marine transgressive events during the late Barremian–?early Aptian. The lateral extension of these marine sediments allows the erection of paleogeographic boundaries that define a « Marginal Folds Gulf » characterized mainly by restricted marine paleoenvironments. This E-W directed gulf is a relatively long depression, a few tens of kilometers wide and one hundred kilometers long, developed in an area which is now at the foot of the eastern High Atlas. The infilling deposits is dominantly controlled by the distance from the North High Atlas Fault. The gulf terminated westward and probably opened northeastward into the Tethyan domain. This narrow gulf was separated from both the Tethyan Gulf known in the Central Middle Atlas during the Aptian and the coeval Atlantic Gulf located on the northern side of the Marrakech and Central High Atlas. Thus, the « Marginal Folds Gulf » is a new paleogeographic feature that documents marine incursions within the Jurassic–Early Cretaceous continental areas of the NW Africa.
The Marmoucha syncline is located in the eastern part of the Middle Atlas. In this syncline, the “Gypsum marls” (Bathonian-?Callovian) are covered by red detrital deposits which outcrop in Aït Bazza ...locality. The upper limit of these detrital deposits is below the transgressional unconformity of the Albian?-Cenomanian marine series. The present work introduces a synthesis of stratigraphical, sedimentological and micropalaeontological studies, which has led to new dating and to the identification of different depositional environments. These results have allowed us to define a new chrono-lithostratigraphic unit, the "Aït Bazza Formation", which comprises three superimposed members AB1-3 separated by two sedimentary discontinuities. This formation, exceeding 300 m in thickness, is formed by conglomerate, sandstone, sand and varicoloured marls. Micropalaeontological bulk sampling in marly horizons revealed associations of charophytes and ostracods, particularly in Member AB2. The charophytes are represented by oogonia of small Porocharaceae, Clavatoraceae such as
Hemiglobator rectispirale
,
Dictyoclavator ramalhoi
, and
Nodosoclavator bradleyi
that characterise the Tithonian. The ostracod microfauna is diverse, consisting of non-marine and lagoonal- shallow marine species at several horizons, associated with sea urchin spines and rare foraminifera, which indicate fluvio-deltaic sedimentary environments subjected to marine influences. This new age constraints of AB2 Mb to the Late Jurassic, and the discovery of marine influences in this eastern part of the folded Middle Atlas, consequently indicates the existence of palaeogeographical connections with the Tethyan domain located to the NE in the Rif foreland.
A 200-m thick carbonate succession has been deposited in shallow-water, saline lake environments during the Priabonian-Rupelian in the Issirac Basin (South-East France). The palaeoenvironmental and ...palaeogeographic significance of such saline lake carbonates has been characterized on the basis of a multi-proxy analysis including 1) depositional and diagenetic features, 2) biological components (molluscs, ostracods, benthic foraminifers, characean) and 3) carbon, oxygen and strontium stable isotopes. Biological associations are indicative of dominantly shallow (<10m), freshwater to mesohaline (0 to 18‰) environments. The occurrence of evaporites is indicative of periods of hypersalinity. Carbonate production is dominantly associated to microbial activity (planar stromatolites) and micrite precipitation in lakes colonized by macrophyte meadows. The Priabonian-Rupelian carbonates from the Issirac Basin recorded three main cycles of lake transgression, corresponding to the three main sedimentary units (U1, U2 and U3). Relative lake-level, degree of connectivity with surrounding lakes and climate (dry versus humid) are the three key factors controlling the water composition, carbonate production and depositional environments in the Issirac lake. Although the ASCI (Alès-Issirac-Saint-Chaptes) lacustrine system likely represents an athalassic (inland) lake system evolving through times, the stable isotope composition (C, O and Sr) of carbonates strongly suggests the occurrence of transient connections of the ASCI lake water with water bodies influenced by seawater and/or fed with sulfates deriving from Triassic evaporites. The Issirac Basin may be therefore interpreted as a sill area connecting the ASCI lacustrine system with the Rhône valley (Mormoiron and Valence) saline lake systems during maximum flooding periods. Finally, changes in depositional features, biota and stable isotope composition of carbonates in unit U3 suggest a transition from relatively dry to more humid climate during the uppermost Priabonian or earliest Rupelian.
•Oligo-mesohaline conditions prevailed in the Priabonian-Rupelian Issirac lake.•Saline lake carbonates recorded three main cycles of lake transgression.•A transition from dry to humid climate is evidenced.•Saline inflows from rhodanian basins during lacustrine transgressions are suggested.
The charophyte flora of the Hamilton Group consists of both vegetative and reproductive organs. The external structure of Sycidium is elucidated by the discovery of antheridial shields at the surface ...of the utricle containing the oospore. The oldest representative of the genus, the Ludlowian (Upper Silurian) Sycidium siluricum (Ishchenko and Ishchenko) which presents the same complex structure, is thus featured as the oldest bisexual plant. Unknown in North America prior to the Lower Carboniferous, the discovery of Sycidium sp. 1 in the Givetian Hamilton Group provides precise evidence of the distribution of Sycidiaceae during the Middle Devonian. Besides Sycidium, the charophyte assemblage includes gyrogonites and oospores, as well as thallus remains; on the whole, the three orders of Charophyta are represented. The fine grey shales of the Plattekill Formation suggest an aquatic, non-detrital habitat, which was certainly suitable to charophyte vegetation. The preservation of delicate structures reflects an absence of transport during fossilization.
•Discovery of Devonian charophytes with both vegetative and reproductive organs•First evidence of monoecia in Sycidium showing antheridia connected to oospores•Sycidium becomes the oldest bisexual plant.•Thallus remains recall Palaeonitella as well as extant Nitelloideae.•First report of Sycidium from the Devonian of North America
Extant genera of Characeae have been assigned to two tribes: Chareae (Chara, Lamprothamnium, Nitellopsis, and Lychnothamnus) and Nitelleae (Nitella and Tolypella), based on morphology of the thallus ...and reproductive structures. Character analysis of fossil and extant oogonia suggest that Tolypella is polyphyletic, the genus comprising two sections, one in each of the two tribes. Eleven morphological characters and sequence data for the Rubisco large subunit (rbcL) were used to reconstruct the phylogeny of genera, including the two sections of Tolypella. Parsimony analysis of the rbcL data, with all positions and changes weighted equally, strongly supports the monophyly of the Characeae. The two Tolypella sections form a robust monophyletic group basal to the family. Transversion weighting yielded the same tree but with a paraphyletic Tolypella. The rbcL data strongly support monophyly of tribe Chareae but tribe Nitelleae is paraphyletic. Parsimony analysis of morphological data produced one unrooted tree consistent with monophyly of the two tribes; on this tree the Tolypella sections were paraphyletic. Combining morphological with rbcL data did not change the results derived from rbcL sequences alone. The rbcL data support the monophyly of the Characeae and Coleochaete, which together form a monophyletic sister group to embryophytes
Pinnoputamen erikfluegeli
and
Sycidium
aff.
volborthi magnum
from Akkuyu (Southern Taurides) are the first Palaeozoic charophytes reported from Turkey, and their presence emphasises the world-wide ...distribution of Sycidiales during the Middle and Upper Devonian. Both species occur in the upper part of the Akkuyu Section of late Givetian through early Frasnian age, based on combined biostratigraphical data. The sedimentary sequence mainly consists of reefal limestones and silt-/sandstones, partly intercalated with shales. In these nearshore deposits, charophytes and open marine fossils, notably brachiopods and conodonts, are found associated. With reference to identical primordial structures of vegetative and reproductive organs both in extant and Palaeozoic forms, and account taken of the prerequisite environmental conditions (such as salinity, light intensity, and nature of substratum), the mode of life in Palaeozoic charophytes was certainly similar to that of modern ones. By a critical review of other fossil occurrences interpreted as marine, we conclude that an allochthonous origin is most probable for the charophytes of the Akkuyu Section.
Examination of Paleozoic charophyte fructifications using microscopy and high-resolution x-ray synchrotron microtomography has revealed that most of them have a utricle that forms a supplementary ...calcified cover around the gyrogonite. All Paleozoic families with utricles have been assigned to the Sycidiales. We consider the Moellerinaceae to occupy a central position in the phylogeny of the Charophyta. From these, one group of descendants constitutes the gyrogonites inside the utricles of the Sycidiales; a second descendant goup is thought to be the utricle-free ancestors of the Charales prior to inversion of spiralization and reduction in cell number. The Sycidiales have a multilayered wall and an internal vesicle, but their families are distinguished by diversity in orientation of external cells, complexity of the utricle wall, and in presence or absence of antheridia. The solidly packed structure of the utricle is believed to be an organ protecting the zygote against dessication. We interpret the morphological similarities between Paleozoic Sycidiales and Mesozoic Clavatoraceae, both with a utricle, as homoplasous rather than expressing a true phylogenetic relationship. We confirm that some umbellids might correspond to utricles of charophytes.
