Argiles De Research Articles

Tracage chimique et isotopique des eaux souterraines en relation avec les eaux de lixiviation de terrils, bassin minier du Nord-Pas-de-Calais (France)

Tracage chimique et isotopique des eaux souterraines en relation avec les eaux de lixiviation de terrils, bassin minier du Nord-Pas-de-Calais (France)

Étude haute résolution de la distribution et de la granulométrie des constituants organiques sédimentaires dans le Kimméridgien–Tithonien du Boulonnais (Nord de la France). Application à l’analyse séquentielle

The sedimentary organic matter from the Kimmeridgian–Tithonian marlstones of the Boulonnais area is studied through a petrographic, geochemical and a grain-size distribution approach. The abundance of the orange amorphous organic matter (AOM) correlates well with the geochemical parameters and intense sulfurisation reactions could explain its preservation, with a relative iron shortage. This may imply strong surface-water productivity linked to sea-level highstands and a possible decrease in sedimentation rate. The OM grain-size parameters correlate with sea-level variations and the orange AOM distribution in the Argiles de Châtillon formation. This relation could be helpful for the comprehension of the sequential stratigraphy.

Sequence stratigraphy of source rocks applied to the study of the Kim meridgian/Tithonian in the north-west European shelf (Dorset/UK, Yorkshire/UK and Boulonnais/France)

In Dorset and Yorkshire (England), the sedimentation of Kimmeridgianfrithonian age (Mutabilis to Pallasioides zones) shows ordered organic sequences. The distribution of the organic matter content (per cent total organic carbon, petroleum potential, hydrogen indices) is not random, but occurs as widespread primary organic-rich cycles nested within each other. These organic-rich cycles, with thicknesses of about 0.5 m, show regular variations in organic carbon contents, reaching a maximum value midway through the cycle. They formed in response to widespread phenomena and can be correlated over long distances. The cycles were deposited in marine environments mainly below the storm wave base; they show little sedimentological evidence of sea-level fluctuation, either transgression or regression. In the Boulonnais (France), a more proximal setting, the comparable strata show a greater lithological contrast and depositional environments corresponding to bathymetric changes are more easily determined. A comparison of the distribution of organic matter through the sequence dated by ammonites, in the three areas studied, shows a good correlation between the distal (Dorset and Yorkshire) and the proximal (Boulonnais) areas. The main result of the biostratigraphic revision in the Boulonnais (France) concerns the Argiles de Châtillon, which can be subdivided into two members. These belong to the Autissiodorensis Zone (Autissiodorensis Subzone) and the Gigas-Elegans Zone, respectively. Thus the Kim meridgian-Tithonian boundary is located within this formation. Transgression does not appear to be the main factor determining the accumulation of autochthonous organic matter (type II). Not every major transgressive facies change seen in the Kimmeridgian/Tithonian of the Boulonnais is characterized by an enrichment in organic matter in the basinal area. Good source rocks with high petroleum potentials result from a conjunction between the physiography, the transgression and the climate. This last causes the variations in primary productivity which produce the organic-rich cycles. Transgressions act mostly to reveal the climatic variations. They are a necessary condition for the accumulation of the autochthonous organic matter, but they are not sufficient by themselves, as demonstrated by the transgressions in the Autissiodorensis and Elegans zones. In the first instance, the strata are depleted in organic matter, in both the distal and proximal areas; in the second instance, type II organic matter accumulated in both distal and proximal environments. The vertical fluctuations in the total organic carbon contents, the types of organic matter and the petroleum potentials of the organic-rich cycles, determine the oil potentials of transgressive sequences in sedimentary basins.

Donnees biostratigraphiques nouvelles sur l'oxfordien et le kimmeridgien du djebel nador de tiaret (avant-pays tellien, algerie); consequences paleogeographiques

In “Djebel Nador de Tiaret” area two calcareous and marly intercalations situated in the upper part of the “Argiles de Faidja” formation contain ammonites of late Oxfordian (Planula zone) and lower Kimmeridgian (Hypselocyclum and Divisum zones). These new biostratigraphic data allow precise correlations with ammoniteless formations. So, the installation of the carbonate platform can be placed in upper Kimmeridgian in all the Western Algeria foreland. Moreover the development of the facies “Argiles de Saïda” into the upper part of lower Kimmeridgian, shows that the closing of the tlemcenian trough begins later in Djebel Nador than in the Ilemcen mountains.

Aspects of late triassic palynology. 2. Palynology of the “grès et schiste à Avicula contorta” and “Argiles de levallois” (rhaetian) of northeastern france and Southern Luxemburg

The present paper (1) provides an analysis of the quantitative/qualitative composition of the palynological assemblages from the “Grès et Schiste à Avicula contorta” and “Argiles de Levallois” of northeastern France and southern Luxemburg, and (2) emphasizes the regional palynostratigraphical potentiality of successive phases recognizable in the gradual compositional development of palynological assemblages from latest Triassic—earliest Jurassic deposits from the Germanic realm. On the basis of the combined presence of Ovalipollis pseudoalatus, Ricciisporites tuberculatus, Rhaetipollis germanicus, Granuloperculatipollis rudis and Corollina spp. the successive assemblages found constitute a single local assemblage zone which may be subdivided into three sub-zones. A proposed scheme of five successive phases in compositional development of palynological assemblages—partly hypothetical in northeastern France and southern Luxemburg—is considered to facilitate realistic long-range palynostratigraphical correlation of latest Triassic—earliest Jurassic successions. The taxonomic part includes: (1) the formal description of the new formgenus Asseretospora; (2) the formal description of the new species Thymospora canaliculata and Duplicisporites kedangensis; (3) emended diagnoses of Rhaetipollis and Acanthotriletes varius; and (4) formal proposals of the new combinations Deltoidospora mesozoicus, Retusotriletes hercynicus, Stereisporites nochtenensis, Asseretospora gyrata and Podocarpidites keuperianus.

NOTES ON THE SPEETON AMMONITES

Anyone who knows a little about the Speeton sections can soon pick up a fairly representative series of their Belemnites, but not of their Ammonites; that demands much time and luck. Such at least has been my experience, for notwithstanding the exceptional opportunities for constant search afforded by several years’ residence almost on the spot, I have not yet found some species, only poor examples of others, and —proof of the exhaustive character of Prof. Pavlow’s and Mr. Lamplugh’s museum and field researches—hardly any that cannot be identified from the descriptions and figures in their “Argiles de Speeton,”[*][1] to which work I am further indebted for the nomenclature and the classification of the series[†][2] used in the following slight sketch. The Ammonites at Speeton are not only in much worse condition than the Belemnites, but also far fewer, except in the Kimeridge where their crushed remains are legion, while in a considerable part of the upper deposits there are apparently none. Of the 43 species described or figured in the “Argiles de Speeton,”[‡][3] all but four, representing as many genera, are included in Hoplites and Olcostephanus, the latter being divided by Prof. Pavlow into six groups, or sub-genera, Virgitates, Craspedites, Polyptichites, Holcodiscus, Astieria, Simbirskites. The Hoplites occupy the lower part of the upper Kimeridge, the extreme top of “the Lateralis zone” D, the lower part of “the Jaculum zone” C, the top of “the Brunsvicensis zone” B, and “the Olcostephani, occur in the upper Kimeridge, the Coprolite Bed E, ... [1]: #fn-1 [2]: #fn-2 [3]: #fn-3

VI.—Note on a large Boulder at Wimpole Hall, Cambs

About five-and-twenty years ago a large boulder, lying in the garden of Wimpole Hall, near Koyston, was pointed out to the Rev. Osmond Fisher by the Lady Hardwicke of that period, and s-he informed him that it had been brought from near Old North Eoad Station when the hill there was lowered. As its dimensions and nature had not been determined, Mr. Fisher invited me to accompany him to Wimpole on April 22nd in order to examine it, having previously obtained permission from the present owner of the property, Lord Eobartes. After a brief search the boulder was discovered lying about 30 yards north-west of the conservatory and almost concealed under a dense growth of ivy. It measures approximately 8 ft. 10 in.inlength, 4 tt.inheight, and lft. 8 in.inbreadth, and consists of a greenish-grey tough sandstone. Mr. Fisher determined its S.G. to be 191 and its weight to amount to 3 tons 2cwt. Lithologically the rock is precisely similar to portions of the Spilsby Sandstone of Lincolnshire, and a specimen in the Woodwardian Museum from near Claxby is indistinguishable from it. By good luck a small Ammonite occurred in a fragment chipped off by the Kev. E. Conybeare, who met us at Wimpole; and Mr. G. C. Crick, of the British Museum, who has kindly examined it for us, writes that it ia “ not referable to any species which has hitherto been recorded from Great Britain, “but that it” is closely related to Olcosteyhanus (Craspedites) subdilus (Trautschold), which has been recorded from the Spilsby Sandstone of Lincolnshire (Pavlow and Lam pi ugh, ‘Argiles de Speetpn,’ etc., p. 116, pi. xiii (vi), figs. 5a, b, c).“