Grey Marls Research Articles

Revised age of proximal deposits in the Zagros foreland basin and implications for Cenozoic evolution of the High Zagros

The regionally extensive, coarse-grained Bakhtiyari Formation represents the youngest synorogenic fill in the Zagros foreland basin of Iran. The Bakhtiyari is present throughout the Zagros fold-thrust belt and consists of conglomerate with subordinate sandstone and marl. The formation is up to 3000 m thick and was deposited in foredeep and wedge-top depocenters flanked by fold-thrust structures. Although the Bakhtiyari concordantly overlies Miocene deposits in foreland regions, an angular unconformity above tilted Paleozoic to Miocene rocks is expressed in the hinterland (High Zagros). The Bakhtiyari Formation has been widely considered to be a regional sheet of Pliocene–Pleistocene conglomerate deposited during and after major late Miocene–Pliocene shortening. It is further believed that rapid fold growth and Bakhtiyari deposition commenced simultaneously across the fold-thrust belt, with limited migration from hinterland (NE) to foreland (SW). Thus, the Bakhtiyari is generally interpreted as an unmistakable time indicator for shortening and surface uplift across the Zagros. However, new structural and stratigraphic data show that the most-proximal Bakhtiyari exposures, in the High Zagros south of Shahr-kord, were deposited during the early Miocene and probably Oligocene. In this locality, a coarse-grained Bakhtiyari succession several hundred meters thick contains gray marl, limestone, and sandstone with diagnostic marine pelecypod, gastropod, coral, and coralline algae fossils. Foraminiferal and palynological species indicate deposition during early Miocene time. However, the lower Miocene marine interval lies in angular unconformity above ~ 150 m of Bakhtiyari conglomerate that, in turn, unconformably caps an Oligocene marine sequence. These relationships attest to syndepositional deformation and suggest that the oldest Bakhtiyari conglomerate could be Oligocene in age. The new age information constrains the timing of initial foreland-basin development and proximal Bakhtiyari deposition in the Zagros hinterland. These findings reveal that structural evolution of the High Zagros was underway by early Miocene and probably Oligocene time, earlier than commonly envisioned. The age of the Bakhtiyari Formation in the High Zagros contrasts significantly with the Pliocene–Quaternary Bakhtiyari deposits near the modern deformation front, suggesting a long-term (> 20 Myr) advance of deformation toward the foreland.

A NEW FAMILY, GENUS, AND SPECIES OF LOBSTER (DECAPODA: ACHELATA) FROM THE GADVAN FORMATION (EARLY CRETACEOUS) OF IRAN

Records of fossil decapod crustaceans from Iran are scarce. Forster and Seyed-Emami (1982) reported Eryma bedelta (Quenstedt, 1857) from the Aalenian (Middle Jurassic) in northern Iran. Garassino and Krobicki (2002, p. 56) noted the presence of the lobster Eryma von Meyer, 1840, from Iran. Garassino (personal commun., 2005) confirmed that this referred to the work of Forster and Seyed-Emami and noted that this was the only decapod occurrence in the country known to him. Toraby and Yazdi (2002) reported a portunid from the Miocene of the country in an abstract but we are unaware of a subsequent publication. Microcoprolites with an internal structure characteristic of decapods are known from the Jurassic of Iran (Bronnimann, 1977). Thus, the discovery of the remains of a remarkable macrurous decapod, recovered from a well core sampling the Gadvan Formation, is noteworthy. This unique specimen is the basis for description of a new family, genus, and species of palinuroid lobster. The Gadvan Formation, named by James and Wynd (1965), has its type locality in the Fars Province at Kuh-e-Gadvan, east-northeast from Shiraz, Iran. It is a part of the progradational Megasequence VI (Alavi, 2004) of deep-marine to shallow-shelf sediments. At the type locality, the formation consists of about 107 m of dark gray, argillaceous, bioclastic limestone interbedded with gray, green, and brownish yellow marl. Laterally, the formation grades into dark shale and argillaceous limestone in the Khuzestan Province, the area from which the decapod was collected. Specifically, the specimen was extracted from a well at latitude 31°18′ 13.3″N and longitude 47°47′28.6″E (Fig. 1), at a depth of 3,852 m in the lower calcareous shale of the lower part of the siliciclastic member of the Gadvan Formation. The unit is the lateral equivalent of the Zubair Formation in Iraq (James and Wynd, 1965 …

Sequence Stratigraphy of Gercus Formation (Middle Eocene) in Sulaimaniya Area, Northeastern Iraq

The Middle Eocene Red Beds known as typical facies of Gercus Formation in north and northeastern Iraq. In the field they cropout as red succession of claystone, lensoidal sandstones and conglomerates. Tectonically the beds are exposed in the folded area of the Zagros Fold-Thrust belt of northeastern Iraq. The whole formation consists of major low stands system tract within stratigraphic record of Tertiary which belongs to 2nd order sea level change. This major lowstand system tract is divided into two depositional sequences named upper and lower sequences which are modulated within 3rd order sea level change. About 90% of its thickness is deposited in the lower sequence, and 10% in the upper one. The lower sequence bounded by SB1 and SB2 from the bottom to the top respectively. It is comprised of SMST, TST and HST. Only the LST of the upper sequence is represented in the Gercus Formation, while the other systems tracts are possibly included in the carbonate of Pila Spi Formation. The SMST consists of alternation of red claystone and marl which are locate at the top of Khurmala Formation. The TST (middle part of Gercus Formation) is composed of grey marl and laminated marly limestone. The HST consists of alternation of red claystone, laminated sandstone and calcareous shale. The LST consists of 1-4m of rounded and sorted conglomerate located at the upper part of Gercus Formation. This system tract is underlain by an erosional unconformity. The inferred depositional environment is most possibly braided delta plain which is prevailed by fresh water influx and flooding by marine water. This is shown in the field by mud cracks, marl marine sediments and laminated sandstone which deposited in upper flow regime.

Effect of plastic deformation in laboratory conditions on magnetic anisotropy of sedimentary rocks

In order to correlate the degree of plastic deformation and low-field magnetic anisotropy, a series of laboratory pressure experiments were carried out on a batch of grey marls. Samples were gradually deformed using triaxial high-pressure device. The confining pressure of 300 MPa was used, yielding maximum relative deformation up to 20% depending upon the uniaxial differential stress. In the range of initial deformation, irregular changes of the anisotropy parameters were typically observed. This effect is related to variable pre-deformation orientation of the anisotropy ellipsoid in the samples. At higher deformation, samples are characterized by increasing degree of magnetic anisotropy and by increasing foliation. Reorientation of paramagnetic phyllosilicate grains due to plastic deformation seems to be the most probable mechanism of the magnetic anisotropy changes.

PALAEGA RUGOSA, A NEW SPECIES OF FOSSIL ISOPOD (CRUSTACEA) FROM MAASTRICHTIAN ROCKS OF TUNISIA

Recent, intensive collecting for Maastrichtian ammonites in Tunisia has yielded a single small isopod specimen from the Kalaat Senaan region. The isopod is a new species of Palaega Woodward, 1870 and appears to be the first representative of the genus to be recorded from the Maastrichtian of northern Africa. A 5,000 m thick sedimentary record, ranging in age from the Aptian to the middle Ypresian, crops out in the west-central part of Tunisia, close to the Algerian border, between Kalaat Senan, Tajerouine, and Kalaa Khasba (see Robaszynski et al., 1990, 1993a, 1993b, 1993c, 2000; Hardenbol et al., 1993; Dupuis et al., 2000; and Steurbaut et al., 2000 for detailed litho- and biostratigraphy) (Fig. 1). An almost 600 m thick marly sequence of the El Haria Formation forms a low, gently undulose landscape, situated between a cliff of the 200 m thick upper limestone bar of the underlying Abiod Formation (which ranges in age from late Campanian to early Maastrichtian) and a cliff of the Eocene nummulitic limestone bar in the Metlaoui Formation. Figure 1 —Map and stratigraphic section showing the geographic and geologic position of the Tabet Zaara Section from which Palaega rugosa n. sp. was collected Numerous gullies deeply eroded into the Maastrichtian El Haria Formation between these two cliffs provide excellent exposures of the 600 m thick sequence. Several lithostratigraphic units are distinguishable within the El Haria Formation, two of which crop out in the Ain Settara section: the lowermost Ain Settara Member, consisting of dark grey jarositic marls with alternating 0.2–0.8 m thick, whitish, carbonate-rich beds, and the uppermost Sidi Nasseur Member, consisting of alternating blue grey marls and thin whitish limestone beds. The base of the Sidi Nasseur marls is defined by a 60 cm thick dark clay, …

A reinterpretation of the Balakot Formation: Implications for the tectonics of the NW Himalaya, Pakistan

The Balakot Formation of the Himalayan foreland basin in Pakistan was originally described as a >8 km thick clastic red bed succession within which are stratigraphically intercalated four gray marl bands containing fossils dated at 55–50 Ma. On this basis, and the reported conformable contact with the underlying Paleocene Patala Formation, the Balakot Formation red beds were interpreted as tidal facies dated at 55–50 Ma, by >20 Myr the oldest foreland basin sediments eroded from the metamorphic orogen. However, our new detailed structural mapping shows the Balakot Formation to be in tectonic contact with the underlying Patala Formation, and the marl bands to be structurally intercalated with the red beds. Hence neither the nature of the Balakot Formation lower contact nor the intercalated marl bands can be used to date the red beds. Our Ar/Ar dating of 257 individual detrital white micas from the Balakot Formation red bed sandstones shows that the red bed succession must be younger than 37 Ma, and we thus conclude that the first exposed foreland basin continental sediments eroded from the metamorphic mountain belt were deposited after 37 Ma, at least 15 Myr later than previously believed. These new structural, stratigraphic, and isotopic data from the Balakot Formation provide new constraints to the early tectonic evolution of the mountain belt, result in reassessment of the facies and provenance of the Balakot Formation, and force reconsideration of models of orogenesis, basin evolution, and the timing and diachroneity of India‐Asia collision that are based on the original documentation of the Balakot Formation.

Les series du Toarcien-Aalenien du SW du Moyen-Atlas (Maroc); precisions stratigraphiques et signification paleogeographique

Abstract Toarcian and Aalenian deposits from south west of the Middle Atlas named "Couches du Seloum", were classically considered as a "border facies" of the Middle Atlas trough, which was extensively developed in the northern part of the folded Middle Atlas. Both studies realized on the border of the Bekrit-Timahdite syncline and the Iguer Awragh-Afennourir syncline, allow to specify the stratigraphy, the spatial distribution of deposits and to reconsider the paleogeographic organization of this "border" in the integral context of the northern Middle Atlas trough during the Toarcian and the lower Bajocian interval. A lithostratigraphic succession of the "Couches du Selloum" raised in the western part of Bekrit-Timahdite syncline shows the superposition of three units. Unit 1 is made of clay, reddish and gray marl, locally gypseous, assigned to the lower Toarcian. Unit 2 is essentially composed of a subnodular calcareous series, which consists of discontinuous, wavy and upward-thickening beds. The upper offshore is the most frequent environment. It is mainly made of crinoidal calcarenites, yielding some ammonites and brachiopods rich levels. The Middle Toarcian (Bifrons zone and Gradata zone) was identified in the lower part of this unit. Most of the upper Toarcian zones were distinguished (Speciosum zone, Meneghinii zone and Aalensis zone), they are represented in the upper part by brachiopods (Stroudithyris) and ammonites (Hammatoceras, Dumortieria and Catulloceras) rich set. On several lateral sections, the uppermost part of these pseudo nodular limestones is dated from Opalinum zone (levels with Leioceras and Tmetoceras). Unit 3 shows several facies: bioclastic calcarenites arranged in decimetrics beds, showing cross stratifications; microsparitic limestones in thick beds with silexites. The macrofauna is scarce, often represented by some crinoidal and mollusks fragments; some Zoophycos appear in the top bed of the set. The following deposits illustrate the evolution from the shoreface to the upper offshore. This unit is overlain by a sedimentary discontinuity, materialized by a boring surface, some pockets of accumulations with belemnites and a cover of ferruginous nodules. Ammonites drowned on the discontinuity surface or in the basis of the first interbedded marls which overlies this surface sign the Aalenian-Bajocian transition (top of the Concavum zone and the basis of Discites zone). Immediately above we found some index fauna of the Laeviuscula zone. The series overlaying the "Couches du Selloum" comprises thinning up alternations of limestone/marl, passing progressively to the "Marnes de Boulmane" Formation. Lateral variations and interpretations; SW to NE variations: The thickness and facies variations observed in the Bekrit-Timahdite syncline (C1 to C9), denote the existence of marine intervals generally more dilated, with some marly deposits developed towards the SW; on the contrary towards the NE, series are exclusively calcareous, reduced in thickness, and often condensed in their upper part. The same evolution is observed between the deposits of the Iguer Awragh syncline to the SW and those of Afennourir in the NE [Benshili et al., 1999]. SE to NW variations: Some observations realized in a Toarcian-Aalenian outcrop recently discovered in the sector of Outghalline (C11), shows that an uplifted area separates the marly basin of Bekrit from the Iguer Awragh one. Such variations denote a partition of the Toarcian Selloum basin, located in south west of the Middle Atlas trough, into several entities which are regrouped under the denomination of "Blocks of Selloum"; two NE-SW trending notably subsiding gutters are recognized, the Iguer Awragh-Afennourir and the Bekrit-Timahdite, separated by a shoal (ridge of Ijadrane). Paleogeographic framework of the SW border of the Middle Atlas trough: A synthesis of the geometry of the "Blocks of Selloum" and some paleogeographic and structural features of the NW border of the Middle Atlas trough, as they appear in a recent synthesis [Benshili, 1989; Elmi et al., 1989; Benshili et Elmi, 1994; Charriere, 1990; Fedan, 1993; Laadila, 1996; Sabaoui, 1998; El Arabi et al., 1999], is shown in 3 episodes from Toarcian to Aalenian. The southwestern part of the Middle Atlas studied here, does not appear in any case as a coastal area surrounding the Middle Atlas trough, but like a gulf occupied by marine deposits which is isolated from the Middle Atlas trough by the shoal areas called the "Haut-fond de Boulmane". In the Middle Atlas trough, the sequences prograde in a NE direction and show blocks tilting generally towards the same direction. On the other hand, in the "Blocks of Selloum" the tilting acts toward the SW, against the direction of the global Tethyan polarity.

Orbital forcing in a ‘Boreal’ Cretaceous epeiric sea: high-resolution analysis of core and logging data (Upper Albian of the Kirchrode I drill core — Lower Saxony basin, NW Germany)

A 245 m (0–245 m subsurface) core of Upper Albian marine sediments from North Germany (research well Kirchrode I) was studied to identify sequences and cycles of sedimentation and related forcing mechanisms on sedimentation in an epeiric sea of the (sub)-‘Boreal’ realm. The core consists of monotonous gray marls with an exceptionally high sedimentation rate of 8–12 cm ka −1. In total, it represents a period of approximately 2.5–4 Ma. A silty glauconite-rich condensed layer marks a change in the succession at 132 m and is paralleled by the first occurrence of E. turriseiffelii and G. bentonensis. The lower part of the core shows lenticular bedding, siderite nodules, average CaCO 3 content of ca. 40% and an abundance of inoceramids ( Inoceramus anglicus, Birostrina lissa, Actinoceramus sulcatus). The upper part is characterised by plane bedding, common siderite layers, an average CaCO 3 content of ca. 35% and an abundance of aucellinas ( Aucellina gryphaeoides). According to lithology and ichnofacies, the succession represents a transgressive–regressive cycle with distinct bimodality of lithology, fossil, and trace fossil content together with reworking and redeposition at the base and top. We studied well-log-data, sediment composition, sediment color, and carbonate content and applied various mathematical analysis techniques to these data (principal component analysis, spectral analysis (Fourier-transform), autocorrelation). Spectral analysis revealed well-pronounced periodic cyclicity in the upper part of the Upper Albian (12, 8, 4.5, 3.4, 1.7 m). The 12 m-eccentricity cycles are the most intense cycles reflecting periodic changes in the terrigenous clastic supply. Chaotic transitional intervals occur around the Middle–Upper Albian, Upper Albian and topmost Albian parts of the core. They are characterised by non-cyclic changes in litho- and biofacies. Mathematically, these changes correspond to singularity points. They are preceded by non-orbital high-frequency variations in carbonate content and in γ-ray.

Sedimentology and geochemistry of fluvio‐lacustrine tufa deposits controlled by evaporite solution subsidence in the central Ebro Depression, NE Spain

The Urrea de Jalón tufa deposits constitute the 20‐ to 50‐m‐thick caprock (0·3 km2) of an isolated mesa. They disconformably overlie horizontal strata of the Tertiary Ebro Basin (NE Spain), which contains a thick succession of lacustrine gypsum and marls, followed by limestones, marls and, locally, fluvial sandstones and mudstones. The tufa deposits show a complex, large‐scale framework of basin‐like structures with centripetal dips that decrease progressively from the base to the top of the tufa succession, and beds that thicken towards the centre of the structure (cumulative wedge‐out systems). These geometries reveal that the tufa deposits were affected by differential synsedimentary subsidence. Distinct onlapping depressions reflect time migration of the subsiding areas. The studied carbonates are composed mostly of low‐Mg calcite, with minor quartz. Some samples have anomalously high contents of Fe, Mn and Ba that may exceed 1% (goethite, haematite and barite are present). Carbonate facies are: (a) macrophyte encrustation deposits; (b) bryophyte build‐ups; (c) oncolite and coated grain rudstones; (d) non‐concentric stromatolite‐like structures; (e) massive or bioturbated biomicrites; and (f) green and grey marls. Facies a and c show a great variety of microbial‐related forms. These facies can be arranged in dm‐ to 2‐m‐thick vertical associations representing: (i) fluvial–paludal sequences with bryophyte growths; (ii) pond‐influenced fluvial sequences; and (iii) lacustrine–palustrine sequences. The Urrea de Jalón tufa deposits formed in a fluvio‐lacustrine environment that received little alluvial sediment supply. Isotope compositions (δ13C and δ18O) reveal meteoric signatures and accord with such a hydrologically open system of fresh waters. The Fe, Mn and Ba contents suggest an additional supply of mineralized waters that could be related to springs. These would have been discharge points in the Ebro Depression of a regional aquifer of the Iberian Ranges. Rising groundwater caused the solution of the underlying evaporites and the synsedimentary subsidence of the tufa deposits.

Dinosaurs nesting on tidal flats

The discovery of a dinosaur clutch in Upper Cretaceous tidal flat deposits in the Tremp Formation in Biscarri, Isona (Lleida, Spain), provides insight into the mode of life of some dinosaurs. The clutch occurs in grey marls that were originally waterlogged, muddy sediments. The seven elongated eggs are parallel to each other and with their long axis almost vertically oriented. A mound-nest is inferred in contrast to hole-nest described so far for similar eggshell types. The permeability of the eggshell (oospecies Megaloolithus siruguei) was highly enhanced by a braided network of multicanaliculate pore canals. The nest style, eggshell porosity and tidal flat environment point to a periaquatic habitat for these dinosaurs. A modern analogue occurs in crocodiles, alligators and some birds living in periaquatic environments, with nesting on plant-mounds above waterlogged soils or even on floating vegetation.

Sedimentary cycles and volcanic ash beds in the Lower Pliocene lacustrine succession of Ptolemais (NW Greece): discrepancy between 40Ar/ 39Ar and astronomical ages

A high-resolution cyclostratigraphy for the rhythmically bedded lignite–marl sequences of the Lower Pliocene Ptolemais Formation is combined with 40Ar/ 39Ar dating results of intercalated volcanic ash beds. Detailed field reconnaissance in three open-pit lignite mines reveals three end-member sediment types: lignites, composed primarily of organic material; grey marls, a mixture of carbonate and organic material; and beige marls, almost exclusively composed of carbonate. These lithologies are arranged in two basic types of sedimentary cycles: lignite–grey marl and lignite–beige marl cycles. A cyclostratigraphic composite section comprising 56 lignite–marl cycles is constructed which combines the consistent cycle patterns from three parallel sections. The concordant positions of 20 volcanic ash beds in these sections confirm the cyclostratigraphic correlations and indicate that the lignite–marl cycles result from regional, basin-wide forcing rather than lateral facies migrations. 40Ar/ 39Ar ages on sanidine and biotite separates from nine volcanic ash beds were obtained by multiple total fusion and incremental-heating experiments. The 40Ar/ 39Ar ages range between 5.00±0.05 and 4.04±0.04 Ma and are, in general, consistent with the stratigraphic order. A least-square linear regression using the measured 40Ar/ 39Ar ages gives an average duration of 21.8±0.8 kyr per lignite–marl cycle. Evidently, the lignite–marl cycles in the Ptolemais Formation are linked to the precessional variation in the Earth's orbit through its influence on Mediterranean climate. For the first time, 40Ar/ 39Ar dating results, totally independent from any other dating and or tuning technique, confirm the astronomical theory of climate change. The 40Ar/ 39Ar ages of the volcanic ash beds show a constant ∼200 kyr (∼4.5%) age discrepancy with the astronomical ages of the same ash beds. This inconsistency remains difficult to explain. The discrepancy is unlikely to have resulted from erroneous astronomical ages, through incorrectness in the astronomical tuning, inaccuracies of the magnetostratigraphic data or the orbital time-series used, and/or errors in the APTS. The 40Ar/ 39Ar dating results neither give clear indications for a possible source of error. From the excellent data set it is evident that neither loss of radiogenic 40Ar, nor an underestimation of the contribution of Ca- and K-derived Ar isotopes could have caused the discrepancy. Moreover, the discrepancy is also beyond the errors in the systematic variables, like the decay constants of 40K or the ages for the neutron-fluence monitors.

Early Jurassic (Pliensbachian-Toarcian) Dinoflagellate Migrations and Cyst Paleoecology in the Boreal and Tethyan Realms

The discrepancies in the stratigraphical ranges of selected dinoflagellate cysts recorded in the Boreal and Tethyan realms have revealed two migrational events during the Early Jurassic. The first event occurred at the early-late Pliensbachian boundary and consists of mutual biotic exchanges between the two realms. This is linked to a major Early Jurassic transgression which improved marine communications between the Boreal and Tethyan areas. The second dinoflagellate migrational event occurred during the mid Toarcian and was driven by paleoenvironmental factors. The numerous available Lower Jurassic dinoflagellate cyst data from the Boreal and Tethyan realms indicates that phytoplankton distribution was profoundly affected by paleoecological factors. Information pertaining to the life strategies and the paleoecological requirements of the genera Luehndea, Nannoceratopsis and Valvaeodinium has also been determined. INTRODUCTION The distributions of dinoflagellate cysts are primarily related to paleoenvironmental regimes. Certain dinoflagellate cyst taxa exhibit heterochroneity over wide areas because of differences in paleoecological preferences and overall paleoenvironments (Goodman 1987). This situation has implications for the application of dinoflagellate cysts to intercontinental biostratigraphy (Bucefalo Palliani and Riding 1997a). During the Jurassic two faunal provinces, the Boreal and Tethyan realms, have been distinguished partly on the basis of different ammonite, foraminiferal, brachiopod and calcareous nannofossil assemblages (Arkell 1956; Gordon 1970; Voros 1977; Bown 1987). Biotic differences between these realms may be characterized by relative abundances rather than by the presence or absence of specific taxa (Hallam 1969). The Boreal Realm occupied the northern part of the Northern Hemisphere; the Tethyan Realm lay to the south (Hallam 1969). During the Early Jurassic a broad transitional area with both Boreal and Tethyan biotic characteristics was developed. This intermediate belt comprises southern France, Hungary and Portugal, and was also delineated on the basis of ammonites, calcareous nannofossils and dinoflagellate cysts (Zeigler 1980; Geczy 1984; Cariou et al. 1985; Gardin and Manivit 1994; Baldanza et al. 1995). Within the Tethyan Realm, the macrofaunas allow the Mediterranean and sub-Mediterranean bioprovinces to be distinguished. The former comprises the northern margin of the Tethys Ocean, thus is of European affinity; the sub-Mediterranean is of African affinity, being on the southern margin of Tethys (Pavia and Sarti 1987). Recently these two Tethyan provinces have been differentiated using calcareous nannofossils (Baldanza and Mattioli 1992; Baldanza et al. 1995; Mattioli 1995). The majority of publications on Lower Jurassic dinoflagellate cysts are from the Boreal domain; there are significantly fewer published data from north-west Tethys. The biogeographical distributions of Lower Jurassic dinoflagellate cysts have not been investigated in detail. On the basis of data by Davies (1985) from central Portugal, Tethyan Lower Jurassic microplankton assemblages are broadly similar in generic/specific content to more northerly floras. However, there are several taxa whose stratigraphical ranges differ profoundly from those in the Boreal Realm (Poulsen 1996; Riding and Ioannides 1996). Recently, palynological studies have been carried out on ammoniteand calcareous nannofossil-dated Lower Jurassic Tethyan sections in order to define the stratigraphical ranges of dinoflagellate cysts and to compare them with their ranges in the Boreal Realm (Bucefalo Palliani 1996). The aims of this study are to distinguish and interpret the stratigraphical discrepancies between the two paleogeographical realms, to utilize the stratigraphical data to identify the areas where the main Pliensbachian-Toarcian speciation events occured, to recognize the most important migrational events and consequently the biogeographical factors which drove the dinoflagellate cyst distributions. MATERIAL Samples were collected from several European Pliensbachianearly Toarcian successions (text-fig. 1). The correlations are based on the ammonite, calcareous nannofossil and dinoflagellate cyst content. The Portugese sections, Peniche, Rabacal and Brehna, are outcrop localities in central Portugal, north of Lisbon (text-fig. 2). The Peniche section ranges in age from the early Pliensbachian (Carixian) to the early Toarcian. It consists of intercalations of marls and more calcareous marls with interbedded black shales and detrital crinoidal limestone. The samples studied are from the Lower Pliensbachian (text-fig. 3). The late Sinemurian (Lotharingian) to early Bajocian Brenha road cutting section was dated by Mouterde et al. (1972). The Lower Pliensbachian portion of the section, made up by grey marls with marly limestone beds, has been investigated during this study (text-fig. 3). micropaleontology, vol. 45, no. 2, pp. 201-214, text-figures 1-12, appendix 1, 1999 201 This content downloaded from 207.46.13.51 on Sun, 19 Jun 2016 05:55:42 UTC All use subject to http://about.jstor.org/terms Raffaella B. Palliani and James B. Riding: Early Jurassic dinoflagellate migrations and paleoecology, Boreal and Tethyan realms

Huit ans de mesures du ravinement des marnes dans les Baronnies méridionales (Préalpes françaises du sud)/Gullying in the South Baronnies (southern French Alps). Results from eight years of monitoring

Abstract The gullying of marls in the southern Baronnies was monitored over a period of eight years. Annual denudation of unvegetated gullies amounted to 2 cm averaged over three years, on divides as well as on gully channels and side slopes. This average is higher in Oxfordian black marls (3,5 cm/year) than in Gargasian blue marls (2 cm/year) and still higher in the Cenomanian grey marls (1 cm/year). Therefore, gully evolution operated without involving any significant change inform. This suggests that the regional drainage network is going through a phase of active entrenchment. This morphogenic evolution is governed by seasonal factors, which themselves involve interannual variation, accumulation being dominant during the cold season, and erosion during the warm season. Canonical correspondence analysis shows that these seasonal contrasts are site-specific in the gully network, affecting mostly the mid-channel topographic positions. The Gargasian marls are affected by in more "paradoxical" seasonal patterns. These dynamics are above all influenced by water but other climatic agents help in reducing clast sizes, during the cold season. Heavy hot season storm showers remove the debris from the channels. Exceeding time-intensities of 50 mm during б minutes such showers occur from May to October included. Stress release in the bedrock is controlled by the depth of the debris mantle. Since the thinning down of the mantle is essentially controlled by climatic agencies, this depth, easily measurable with a hand-penetwmeter, may constitute an indicator of the erosivity of climate and a proxy for the estimated denudation rate. Clast size may constitute another indicator of marl sensitivity to erosion.

Conodont biostratigraphy of uppermost Triassic deep-water calcilutites from Pizzo Mondello (Sicani Mountains): Evidence for Rhaetian pelagites in Sicily

Rhaetian pelagites are described for the first time from Western Sicily in the Pizzo Mondello area (Sosio Valley, Sicani Mountains) where a thick pile of Upper Triassic cherty calcilutites outcrops. The Upper Triassic pelagic calcilutites of Pizzo Mondello are divided into three lithostratigraphic units. The lower unit consists of a few meters of dark gray marls and clay marlstones (equivalent to the Mufara Fm.) of Carnian age followed by Halobia-bearing cherty limestones (about 300 m thick) of Late Carnian—Late Norian age. The upper unit consists of white calcilutites and grey-greenish marls containing the conodonts Misikella posthernsteini and Zieglericonus rhaeticus of Rhaetian age. These Rhaetian deposits are here informally named as Portella Gebbia Limestone. In the Pizzo Mondello succession the Norian/Rhaetian boundary, sensu Kozur and Mock (1991), can be approximated along the lowermost calcilutite bed of Portella Gebbia Limestone containing the first occurrence of M. posthernsteini.

Woody plant roots fail to penetrate a clay-lined landfill: Managment implications

In many locations, regulatory agencies do not permit tree planting above landfills that are sealed with a capping clay, because roots might penetrate the clay barrier and expose landfill contents to leaching. We find, however, no empirical or theoretical basis for this restriction, and instead hypothesize that plant roots of any kind are incapable of penetrating the dense clays used to seal landfills. As a test, we excavated 30 trees and shrubs, of 12 species, growing over a clay-lined municipal sanitary landfill on Staten Island, New York. The landfill had been closed for seven years, and featured a very shallow (10 to 30-cm) soil layer over a 45-cm layer of compacted grey marl (Woodbury series) clay. The test plants had invaded naturally from nearby forests. All plants examined—including trees as tall as 6 m—had extremely shallow root plates, with deformed tap roots that grew entirely above and parallel to the clay layer. Only occasional stubby feeder roots were found in the top 1 cm of clay, and in clay cracks at depths to 6 cm, indicating that the primary impediment to root growth was physical, although both clay and the overlying soil were highly acidic. These results, if confirmed by experimental research should lead to increased options for the end use of many closed sanitary landfills.

Significado estratigráfico y tectónico de los complejos de bloques resedimentados cambro-ordovicios de la Precordillera Occidental, Argentina

Rocks belonging to the Early Paleozoic Los Sombreros Formation crop out on the eastern flank of the Sierra de Yerba Loca, along the Rio Jachal section. This Formation consists of black shales and turbidites with interbedded limestone boulders near the base of the section, one of them up to 200 m long and 30 m thick. Boulders yield both early Cambrian trilobites and early Ordovician conodonts. Near the top, a thick sequence of dark grey marls and limestone contains an early Middle Cambrian trilobite fauna which is overlain by limestone and calcareous turbidites containing early Llanvirn graptolites and conodonts. On the basis of paleontological and sedimentological evidences this sequence can be interpreted as a series of submarine gravity slides interbedded within a dominantly turbiditic sequence. The Cambrian-early Ordovician precordilleran carbonate platform served as the source for much of the sediment which was redeposited on the slope. Then, deposition of the early Ordovician Los Sombreros Formation could be related to uplift and erosion of the platform margin and steeping of the slope during the late Arenig-early Llanvirn.

Die Obere Meeresmolasse (OMM) am Pfänder: Beispiel eines Gilbert-Deltakomplexes

The 470 m thick Upper Marine Molasse (OMM) of the Pfander (Vorarlberg, Austria) comprises the Luzern and St. Gallen Formations (Burdigalian, Lower Miocene) and displays three facies associations, each composed of several lithofacies (LF). The wave-dominated facies association is made up of lithofacies A-E, which represent a spectrum of coastal sedimentary environments. Grey marls with erosive based sondstones (LFA) record alternating fair-weather and storm conditions in the offshore-transition zone. Lithofacies B-E comprise well-sorted sandstones showing a variety of sedimentary structures, such as symmetrical wave-ripples, transcurrent- and parallel-lamination, and were deposited at the lower and upper shoreface and the foreshore

Bois de coniférales dans l'Albien du synclinal du Beausset (Var, SE France): Signification paléogéographique et paléoclimatique

The Upper Albian grey marls of Sainte-Anne-d'Évenos area (Var, SE of France) have yielded several fragments of fossil woods associated with marine deposits where pelagic organisms are in abundance. Two homoxyleous structures of Coniferales Cheirolepidiaceae have been identified: Brachyoxylon brachyphylloides (Torrey) Kräusel and Brachyoxylon sp. One of these structures is identical with Lower Cretaceous specimens discovered in Eastern USA, and in the future site of Tethys-Benue sound. Climatic and ecological conditions have been inferred from certain anatomical features (growth-rings) as well as from palynological and sedimentological analysis. A palaeogeographic reconstruction of Basse-Provence during Late Albian is suggested.

Geotechnical properties of the Corinth Canal marls

The Corinth Canal crosses the isthmus of Corinth and is of great importance for Mediterranean navigation as well as the railroad and highway connections between southern and central Greece. In the century-long history of the Canal, the slopes have shown only minor stability problems despite their significant length, very steep inclination and, more importantly, the strong earthquakes that have frequently shaken the Corinth area. This type of unsual behaviour has motivated research into the mechanical behaviour of the bluish grey marl which is the main geological formation in the Canal area. Geotechnical investigation of the Corinth Canal marl was performed with an extensive laboratory testing programme on high quality undisturbed samples of the intact marl. The material was shown to exhibit brittle behaviour, high stiffness and significant apparent cohesion at low and moderate stress levels. These characteristics indicate that the material possesses significant structural bonding which is believed to be due to cementation between individual particles, caused by the deposition of carbonates at the time of material genesis. With stressing, the material yields due to a gradual bond degradation. The locus of the initial yield points (yield surface) seems to be an ellipse oriented along the isotropic axis. The testing programme was supplemented with a series of tests on the de-structured marl obtained by thorough remoulding. These tests showed a significant difference in the pre-yield stiffness and the peak strength at low stress levels, but comparable post-rupture shear strengths.

Les Diastopora (Bryozoaires cyclostomes) néocomiensdu Jura suisse et français

Under the name Diastopora are grouped tubularspecies hitherto assigned to the genera Diastopora and Entalophora. The diameter of the axial canal, a character used to separate the two genera, is partly correlated with the diameter of the stems and often with environmental factors. This character appears too variable; sometimes the stems of one colony would be placed two genera. The affinity of Diastopora with Mesentéripores is proved by the similarity of the three principal types of ovicells. The acknowledgement of three types of ovicells involve the distribution of the species in three groups. Perhaps, this is a first step towards the dismemberment of the genus Diastopora.Six species of Diastopora were found in the Neocomianof the Jura. Two are new: D. alata and D. compacta. The predominance of these species changes with stratigraphical position, paralleling lithofacies. D. tubulosa is dominant in the Lower Valanginian (hard or sandy bottom in agitated water?), but decreases in the Upper Valanginian (chiefly Calcaires à Alectryonia and marls rich in fragments of bivalve shells; shelly, sandy bottom with little mud) where D. alata becomes dominant. Finally, Diastopora with perforated ovicells (D. brunsvicensis, D. canaliculata, D. salevensis appear and replace the previous species during the Upper Valanginian and Lower Hauterivian, with expansion of the grey marl facies (muddy and deeper bottom?).