Sandy Series Research Articles

Paleozoic Gondwanan structure along the Maule river valley between Toconey and Constitución (35.4°S, Chilean Pacific Coast)

During the late Carboniferous–middle Permian, the basement of the Chilean Coastal Cordillera was deformed by the Gondwanan Orogeny, developed by the subduction of the Paleo-Pacific plate under Gondwana from the early Carboniferous. In the Maule sector (35.4°S), the following metamorphic rock units are distinguished: (i) Western Series, formed by metapelites, metabasites, metacherts, metaconglomerates, and marbles, mixed in a subduction channel, with probably ages between the Cambrian and the Carboniferous; (ii) Eastern Series, consisting of metasediments of a fore-arc basin, Carboniferous in age. In the Eastern Series two units are recognized in terms of lithology and deformation style: the Eastern Pelitic Series and the Eastern Sandy Series. Three Gondwanan deformation episodes have been distinguished, affecting both series unequaly. In the Western Series, D1 structures consist of a foliation (S1) developed under high-pressure and low-temperature conditions, while in the Eastern Series it comprise tight east-verging folds, with the associated S1 developed under low PT metamorphic conditions (greenschist facies). D2 structures are only present in the Western Series and Eastern Pelitic Series and represent the exhumation of the accretionary prism and its emplacement to the east over the fore-arc basin, with the development of east-verging recumbent folds and a thick shear-zone. Difficulties in the propagation of the deformation by the presence of the Coastal Batholith to the east led to the development of the D3 deformation event, only well developed in the Eastern Sandy Series, and represented by the Los Tablones Back-thrust and associated folds, as well as N–S open right folds formed under low PT metamorphic conditions.

Upper Pleistocene palaeoenvironmental changes at the Zwierzyniec site, central Poland

The paper presents the data on an Eemian–Late Glacial sedimentary sequence from the Zwierzyniec site, central Poland. A number of boreholes document one or two organic layers that occur beneath one or two horizons of clayey and silty deposits of ice-dammed lakes. This study demonstrates to which extent the Zwierzyniec site can contribute to a better understanding of the palaeoenvironmental changes during the Eemian–Vistulian time-frame in central Poland. To study it, a multi-proxy approach was applied, involving: palynological and plant macrofossil analysis, study of rounding of quartz grains and morphology of their surface, and investigations of sand mineralogy and till petrography. The results show that a till bed is overlain by a sandy series corresponding to the glacial-interglacial transition. Either one or two distinct peaks of organic accumulation are evidenced by peat horizons. The lower horizon records spectra with hazel and hornbeam, and did, therefore, accumulate in the Eemian. Observed only in some boreholes, the upper peat horizon marks the Brorup (or the lower part of the Rederstall stadial) represented by forest-steppe conditions with patchy mosaics of larch and further transition into sedges and herbaceous taxa. Localized in between the two peat sequences, the sandy horizon marks a long-lasting aeolian transformation with weathering by frost in the Early Vistulian. Again, significant changes of the palaeoenvironmental regime occurred, and are manifested in the one or two horizons of the glaciolacustrine sediments. This corresponded to the last glaciation in the region, when the ice-dammed lakes formed during the Main Stadial.

Environmental significance of Upper Miocene phosphorites at hominid sites in the Lukeino Formation (Tugen Hills, Kenya)

The Lukeino Formation contains an important sedimentary and fossiliferous record of the late Miocene (6.09–5.68Ma), which has in particular yielded the fossil remains of the oldest East African bipedal hominid called Orrorin tugenensis. This fluvio-lacustrine sedimentary succession crops out in the Kenyan part of the East African Rift. It is mainly composed of clay to sandy clay deposits intercalated with volcanic ash horizons, and localized layers of carbonates and diatomites. A detailed sedimentological and mineralogical study of the Lukeino Formation was conducted to throw light on the environmental conditions in which the hominids lived.Several centimetric, relatively continuous and indurated phosphatic horizons, of sedimentary origin, were identified at two sites (Sunbarua and Kapcheberek). Mineralogical (XRD) and geochemical analyses as well as observations by SEM, which was coupled with an energy dispersive spectroscopy (EDS) microprobe, indicate that the autochthonous phosphate layers are composed of a micritic matrix of francolite (38–93%), with incorporation of silicates in variable proportions from one layer to another. The phosphate matrix contains very well preserved and abundant diatom frustules in the basal phosphate layer. These diatoms are identified as Aulacoseira granulata, implying a pH of 7.8–8.2 for freshwaters of the Palaeolake Lukeino. Calcitic tubular structures, linked to a possible bacterial origin, are also observed locally.Phosphate layers occur abruptly within a thick clay–sandy series, associated with an intense runoff phase during the deposition of this interval of the Lukeino Formation. The massive and cyclic input of phosphorus to the lake promoted productivity to the stage where it caused a diatom bloom. The establishment of several phosphate horizons testifies to successive phases of eutrophication of Palaeolake Lukeino. The diatom cells provided some of the organic matter, which was decomposed by bacterial activity at the bottom of the lake in suboxic conditions, but in insufficient quantities to fully form the phosphatic materials. The rest of the organic matter needed for phosphogenesis came from terrigenous supply (plant debris), suggesting the presence of dense vegetation in the catchment of the Palaeolake Lukeino, during this well-drained interval of deposition of the Lukeino Formation.

The wild river and the last Neanderthals: a palaeoflood in the geoarchaeological record of the Jarama Canyon (Central Range, Guadalajara province, Spain)

The Upper Jarama Valley is located on the southern slope of the eastern part of the Spanish Central Range. In this area the valley cuts and runs through a narrow strip of carbonated rocks creating a karstic canyon with many caves and rock shelters in the cliffs at both banks. One of this rock shelters, Jarama VI, is located on the left bank of the Jarama River, in the middle of a hillside, 23 m above the river, and is partially filled up. The lithostratigraphic sequence begins with the, stratum alteration (unit 4), and a cold autochthonous clastic deposit follows it with a human occupation of the Middle Paleolithic (unit 3). The upper part of the unit 3 was affected by a strong erosion due to a huge palaeoflood, which caused the sedimentation of a sandy series (sub-unit 2.3) that ends in flood silts (sub-unit 2.2). Charcoals have yielded the 14C date 32.600 ± 1.860 BP (Beta-56639). These deposits have their origin in a fluvial palaeosuperflood. At the top part of this level and inside the rock shelter there are clastic intercalations (sub-unitl 2.1) with plenty of Mousterian artefacts radiocarbon dated to 29500 ± 2700 BP (Beta-56638). A stratigraphic hiatus separates units 2 and 1. Unit 1 is a cold autochthonous clastic deposit containing many human occupation remains of the Early Upper Paleolithic age. The sequence is sealed by a stalagmitic crust (unit 0). The 14C dates from Jarama VI seriate the palaeoflood in the chronostratigraphic scale. Therefore, both dates 32600 ± 1860 BP (Beta-56639) and 29500 ± 2700 BP (Beta-56638) date the upper part of level 2 somewhere in the Late Upper Pleistocene, between the isotopic stages 3 and 2.

Alluviation in the Meurthe and Moselle valleys (Eastern Paris Basin, France): Lithological contribution to the study of the Moselle capture and Pleistocene climatic fluctuations

Geomorphological and lithostratigraphic analysis allow the definition of a record of eleven alluvial stepped units in the Meurthe valley downstream from the Vosges Massif. The deposits are mainly composed of sands derived from Permo-Triassic strata. A similar system of stepped terraces is identified in the Moselle valley near Toul, where the deposits are coarser and contain more crystalline sediments than those of the Meurthe. A distinction is made in these units between the levels deposited before the capture of the Upper Moselle river by the Paleo-Meurthe, which follow the former course towards the Meuse valley, and the post-capture levels, which follow the modern valley Downstream from the present Moselle-Meurthe confluence, the higher deposits (above 25 m relative height) are similar to the Meurthe sediments (Permo-Tnassic origin), as opposed to the youngest deposits (0 to 25 m relative height) which contain crystalline sediments from the Upper Moselle basin. This contrast allows the Moselle capture to be positioned between formations F4 and F3 of the alluvial system downstream from the present confluence. The correlation between these sections of valley underlines the parallelism of the terraces and the weakness of the syn-capture altitudinal gradient between the Upper-Moselle and the Paleo-Meurthe rivers. In certain parts of the valleys, a contrast is shown between sandy hthofacies from the Permo-Tnassic cover and coarse hthofacies with crystalline elements. The deposition of the sandy series is attributed to full-glacial episodes, while that of the coarse series is correlated with periods of retreat of the Vosgian glaciers, especially during lateglacial episodes. The consensus of absolute dates of the capture (250-300 000 years B P) allows the incision rate for the Meurthe and the Moselle valleys to be estimated at 0 1 1 mm/y-1 since the capture. This rate is comparable with the rate already obtained for the Moselle valley in Germany.

New lithostratigraphical, sedimentological, mineralogical and palaeontological data on the Mesozoic of Belgian Lorraine: a progress report

A multidisciplinary study of some extensively cored boreholes together with the new 1/25,000 geological mapping of Wallonia led us to propose a new lithostratigraphic canvas for Belgian Lorraine. This area is located on the N-E border of the Paris Basin, south of the Ardennes; the studied stratigraphic interval covers the Keuper to the Toarcian. Each of the new lithostratigraphic units is interpreted by macroscopic and microscopic sedimentological observations. Detailed palynological and claystratigraphical analyses were also performed, providing additional stratigraphical, palaeoecological and sedimentological data. The Habay Formation (conglomerates and red mudstones) is a fluvial unit, with immature channel conglomerates and paleosoils. The Attert Formation (dolomitic marls with gypsum and pseudomorphs) exhibits an evaporitic trend. The Mortinsart Formation (sands and marls) corresponds to a restricted marine unit, evolving towards an alluvial plain (Levallois Member). The second cycle begins with the Jamoigne Formation (bioturbated marls and limestones), a marine subtidal restricted unit, evolving towards a more sandy series (Metzert Member). The base of the third cycle corresponds to the rest of the Luxembourg Formation, composed by a superposition of sand waves. The Ethe Formation (laminar mudstones and marls) marks a deepening of the basin and the outset of marine dysaerobic conditions. The Aubange Formation (bioturbated marls with sandstones and limestones) is characterized by the reappearance of a normal benthic fauna. The Grandcourt Formation (laminar mudstones and marls) marks a return to open marine dysaerobic conditions. The Mont-Saint-Martin Formation (marls, sandy marls and oolitic ironstone) is a highly regressive unit, while the Longwy Formation (limestones) marks the initiation of a carbonate platform.

Nouvelles découvertes de Vertébrés miocènes dans le synclinal de Dera Bugti (Balouchistan, Pakistan)

Since Forster-Cooper in 1910, no paleontologist bas visited the area of Dera Bugti in Baluchistan (Pakistan). In 1995 and 1996, two small French expeditions prospected the syncline of Dera Bugti. They established stratigraphical sections ana discovered many fossils, mainly reptiles, and mammals. On top of the Eocene marine limestone of the Kirthar there lies a Burdigalian marine falun. Above, about 250 m of continental marls, sands and sandstones are deposited. The first 100 m have yielded five fossiliferous levels of MN3 b in age, and one of MN4, surrounded by a more sandy series. The top of the series has yielded Hipparion of the Upper Miocene.

Sequence stratigraphy and micropaleontology of the Triassic series from the southern part of Tunisia

The Triassic series in the southern part of Tunisia, only known from the oil exploration wells in the Kirchaou area (sandy series from Early Scythian to Ladinian) and in its Djeffara/Dahar-North outcrops (alternating series from Ladinian to Rhaetian) is now subdivided into 10 Depositional Sequences (DS) sensu Vail et al. (1987), T 1 to T 10 corresponding approximately to most of the 3 rd order eustatic cycle from the Haq et al. curve (1987). Within the DS succession, 3 basal discontinuities (or sequence boundaries) appear to be important in Tunisia: the base of T 2, correlated to the “H Discordanz” from the “Germanic Triassic” (intrascythian); the base of T 6 (intracarnian), well-marked by the Sidi Stout angular discordance from Dahar North; the base of T 8 (intranoirian additional DS, previously recognized in Germany) pointed by the cartographic discordance of Low Stand conglomerates. The shallow-water facies from the carbonate Transgressive Systems Tracts of 7 Tunisian DS contain macrofauna, such as Myophoria, and particularly 6 successive benthonic Foraminifera assemblages, F 1 to F 6 giving chronostratigraphic informations as complement of Palynomorphs and Conodonts. Belonging to the genus Meandrospira, Triadodiscus, Aulotortus, Lamelliconus, Endothyranella, Pilamminella, Agathammina, Gandinella etc.…, most of them, commonly used as zone-indices in Europe, are new in Tunisia.

Nouvelles observations sur la serie de la Gara Sayada (bordure nord-est de l'Eglab, Sahara occidental)

Abstract A subhorizontal sandy series, the Gara Sayada series, some hundreds of meters thick, overlies a folded sandstone-shale series, more than 1,000 meters thick, on the north-eastern margin of the Eglab massif (Algeria) in the western Sahara. The intra-Caradocian (Ordovician) unconformity already known at several other localities in the Sahara is thus also represented in this region.

Note on Cambrian Hyolithes Sandstones from Nuneaton

The fossiliferous rocks belonging to the now famous Olenelluz Zone or basement Cambrian series were practically unrecognised by the majority of geologists ten years ago. They are now, however, known to have an almost universal extension on both continents north of the Equator, from India to Lapland in the Old World, and from Virginia to British Columbia in the New. Fossiliferous beds belonging to this Lower Cambrian zone have been recently found to occur in their proper place among the well-known Cambrian quartzites of Nuneaton and Atherstone, and the fossils, which are many of them well-preserved, include Hyolithes, Coleoloides, Kutorgina, Sccnella , etc., of the same type as those which occur in the lowest Cambrian rocks of Scandinavia and Newfoundland. The first indications of fossils in this Midland zone were detected by Dr Stacy Wilson in July 1895, and the actual fossil-bearing beds were subsequently followed and worked out in the field by myself. It is exceedingly interesting to find the same general succession of Cambrian rocks in the English Midlands as in all those regions in Britain and abroad, where the well-known Cambrian quartzite band forms the lowest bed of the Cambrian system. The fossil-bearing layers in the Midlands come in, as usual, between two sets of arenaceous strata, namely between a lower sandy series—the well-known Nuneaton or Lickey quartzite—and a higher and thinner arenaceous series, which appears to be the local equivalent of the well-known Salterella Grits and Hollybush Sandstone of other districts. It thus becomes more clearly evident

Supplementary Note on the Walton-Common Section

There seems to be so much uncertainty as to the character of the basal beds of the Lower Bagshots in the London Basin that any opportunity which affords us unmistakable evidence of their real nature should be seized without delay. We have had so much theorizing, based upon the evidence of well-sections and of limited exposures, that we turn with pleasure to a good continuous section like the one which has lately been disclosed between Walton and Weybridge on the London and South-Western Railway. The main features of the Lower Bagshot series in this section, at its actual junction with the London Clay, were very fully described by me in a communication made to the Society last year. Whether we regard the junction there shown as evidence of an unconformity or otherwise, the fact of a complete lithological change is patent to all. 1. Recapitulation of some points in the previous paper. Resting immediately upon the grey-coloured and sticky London Clay, distinguished by its fine and perfectly regular bedding, is a sharp yellow sand full of current-bedding. This yellow sand I dabbed “No. 1 Bagshots.” Then follows the first clay series, which I called No. 2, or the “Blue Bagshots.” It is surmounted by a second sandy series, referred to in my previous paper as “No. 3 Bagshots.” As far as the new cutting for the widening of the line had then progressed, there was no reason to suppose that No. 3 was succeeded by a second clay series, beyond

IV.—Woodwardian Laboratory Notes

The district to which the following notes refer is that which lies between Bagshot, Woking, Aldershot, Farnborough and Ascot. It consists mainly of heath-land, and seems but little known to geologists; in fact, the only authority for the beds included in this area is Professor Prestwich, who, in his paper on the Bagshot Beds [Q.J.G.S. vol. iii. (1847), p. 278], has supplied all the information about the district that is at present known. He divided the beds into an Upper Sandy series, a Middle Clayey series, and a Lower Sandy series. The Middle series he grouped with the Braeklesbantts of the Hampshire basin. The Upper he placed between the Bracklesham and Barton ; our present object is to show that it is more nearly related to the latter.

On the so-called Midford Sands

At the village of Midford, some three miles to the south of Bath, is a fine section of the upper beds of the Inferior Oolite rock, consisting of a cap of oolitic freestones of some 20 feet in thickness, resting upon a mass of sand, of which 25 feet are exposed at the station, and which presents all the features of the sand at Bradford Abbas and Bridport Harbour, as the sands are loose, vary in colour, and present occasional bands of hard compact stone. From these sands being so well shown at this place, Prof. Phillips was induced to name them, after the village, the “Midford Sands;” and he thus writes upon the section:— “If we wish to draw a hard limit of mineral deposits, it should probably be between the sand and its calcareous cover (which is often absent); but if we desire to study organic sequence, we shall unite the sands and their shelly cap into a transition group”*. Now as this “shelly cap” is the one so highly charged with Cephalopoda we further quote the following :— “The ‘Cephalopoda-bed,’ as Dr. Wright proposes to call the cap limestone of this sandy series, exists where the shells to which it owes its name were specially abundant, or by some natural circumstances were brought together. It is not known in the valleys of the Cherwell or Evenlode, and very partially in any of the branches of the Windrush, Coln, or Churn; but on the western front of the