Showing papers in "International Journal of Earth Sciences in 1984"

Tectonic evolution of the basement complex in the central eastern desert of Egypt

Abstract: The Egyptian basement rocks are gathered into three major rock groups, viz. Meatiq Group (oldest), Abu Ziran Group and Hammamat Group (youngest); the last two groups belong to the Pan-African orogenic cycle. The Meatiq Group is an old crystalline basement cropping out in gneiss domes. The Abu Ziran Group comprises the geosynclinal association which is formed of a lower ophiolite unit overlain by metasediments, volcanoclastics and locally intermediate volcanics having clear island arc characters. The Hammamat Group comprises molasse-type clastics, and penecontemporaneous Dokhan Volcanics of andesite to rhyolite composition; syn to late-tectonic calc-alkaline granites are the plutonic equivalents of the Dokhan Volcanics.

A geological study of lake van, Eastern Turkey

Abstract: Lake Van is a lake with a volume of 607 km3 and a maximum depth of 451 m in a tectonically active zone in eastern Anatolia. It may be divided into three physiographic provinces: lacustrine shelf, sublacustrine slope and lake basin. The shelf is largely made up of submerged fluvial valleys and alluvial plains, as evidenced by the local occurrence of karst-like topography, buried, leveed river valleys and sediment wedges interpretable as relict deltas. The shelf and basinal deposits are characterized by an alternating succession of well-stratified and chaotically reflecting layers consisting of turbidites and slump deposits respectively. This thick sequence of unconsolidated to consolidated sediments is underlain by a Paleozoic metamorphic or Upper Cretaceous limestone basement.

Alkaline character of Eocene volcanism in the middle part of central Iran and its geodynamic situation

Abstract: Alkaline volcanic rocks, sometimes feldspathoid bearing, appear in variable stratigraphic positions within the Eocene of the middle part of Central Iran No magmatic zonation and no K2O enrichment in both time and space can be found in this volcanic sequence These facts together with other geochemical and geological features of the Iranian Eocene provinces do not agree with a volcanism related to a subduction zone model

Suevite of the ries crater, Germany: Source rocks and implications for cratering mechanics

Abstract: Suevites are impact breccias with a montmorillonitic matrix that contains shocked and unshocked mineral and rock fragments from the crystalline basement, glass inclusions and a small amount of sedimentary clasts. Data are given of the modal composition of fall-out suevites (deposited at isolated points around the crater) and crater suevite (forming a layer below post-impact lake sediments in the crater cavity). Fall-out suevites contain aerodynamically shaped bombs which are absent in crater suevite. Taking into account not only large glass fragments and bombs, but also the finer fractions, the glass content of fall-out and crater suevites amounts to 47 and 29 vol%, respectively. Crystalline clasts in suevites consist of all igneous and metamorphic rock types that constitute the local basement which consists of an upper layer of igneous rocks (mainly granites) and a lower series of gneisses and amphibolite. Based on a collection of 1 200 clasts from 13 suevite occurrences the average crystalline clast population of suevites was determined. Suevites contain on the average 46 % igneous and 54 % metamorphic clasts. In constrast, weakly shocked and unshocked crystalline ejecta of the Ries structure consist of 82 % igneous and 18 % metamorphic rocks.

The eruptive center of the late quaternary Laacher see tephra

Abstract: About 5 km3 of phonolite magma were erupted 11,000 years ago in the Laacher See area in Plinian and Vulcanian eruptions. The eruptive vents for all tephra, in dispute for over 200 years, must have been located entirely within the Laacher See basin, because: (1) All deposits are thickest in the tuffring surrounding the basin, with one exception: pyroclastic flow deposits are thickest 2 to 6 km away from the rim of the basin having ponded in radial valleys. Three Plinian fallout layers show minor secondary thickness maxima 12 to 16 km east of Laacher See. (2) Axes of all depositional fans and single tephra sheets converge in the Laacher See basin. (3) Diameters of both lithic and pumice clasts reach their maxima in outcrops close to Laacher See volcano. (4) Directions of asymmetric ballistic impact sags indicate the Laacher See basin as source area. (5) The dimension of Laacher See crater roughly corresponds to the erupted volume of phonolitic tephra (5.3 km3 magma DRE) and lithic clasts (0.7 km3). (6) Xenolith types are consistent with an eruptive center within the Laacher See basin. (7) The systematic chemical and mineralogical zonation of the tephra deposits — from highly differentiated aphyric phonolite at the base to highly phyric mafic phonolite at the top — strongly suggests eruption from a single compositionally zoned magma column. (8) Several lines of evidence indicate migration of the main eruptive focus from the south to the north during the later part of the eruption, both vents however being confined within the Laacher See basin.

Lower Cretaceous turbiditic sediments from the Rif chain (Northern Marocco) - palynology, stratigraphy and palaeogeographic setting

Abstract: The paper describes the palynology, stratigraphy, sedimentology and palaeogeographic setting of Lower Cretaceous turbiditic and terrigenous deep-sea sediments at the Tethyan margins of Africa and Alboran (External Domain of the Rif, and Flysch Nappes)

A model for the tectonic evolution of the Benue Trough of Nigeria

Abstract: Based on the results of a detailed magnetic study of the Lower and Middle Benue Trough of Nigeria carried out by the author and results of previous geophysical studies of the Benue Trough and of similar structures elsewhere in the world, a possible model for the tectonic evolution of the Benue Trough has been developed. It is here suggested that the tectonic evolution of the Benue Trough of Nigeria involved the rise of a mantle plume or mantle upwelling, emplacement of intrusive igneous material in the crust, crustal stretching and thinning and consequently rifting. It is thought that this sequence of events may have been repeated in a cyclic manner with intercyclic structural deformations. The basic ideas of the model is shown to be in agreement with acceptable ideas on riftogenesis.

Chemical variation in a Proterozoic suite of granitoids extending across a mobile belt — craton boundary

Abstract: Contrary to earlier opinions, the southwestern margin of the Baltic Shield was formed after the Svecokarelian orogenic event (2.2-1.8 Ga). During the initial stages of its formation (1.7-1.6 Ga), granitoid rocks intruded the southwestern margin and simultaneously also the already cratonized part of the shield. Among these granitoids, the most important chemical difference is between calc-alkalic differentiated granitoids to the west and alkalicalcic more evolved granites to the east of an intraorogenic “suture” (the Mylonite Zone). The chemical differences between alkali-calcic granites found on both sides of the interorogen boundary proper (the Protogine Zone) are less significant. As yet, a final choice cannot be made between wholly actualistic and non-actualistic, possibly intracratonic(?) variants of precursory plate-tectonic processes.

Concepts of the evolution of the Austroalpine basement complex (Eastern Alps) during the Caledonian-Variscan cycle

Abstract: The Austroalpine basement complex has a complicated pre-Alpidic history which begins with the Caledonian era. In the late Precambrian (?) and early Paleozoic a magmatic-sedimentary rock sequence is formed presumably in an island-arc or active continental margin environment. Subduction with eclogite formation is followed by collision, high-grade metamorphism and anatexis in the Ordovician. This Caledonian basement is preserved in parts of the Austroalpine crystalline mass. The post-Caledonian deposits are mainly shelf type sediments with intercalated volcanics, although there is evidence for an oceanic basin to the south. The Variscan facies zones are arranged in SW-NE direction, oblique to the Alpidic trend. In a first stage of Variscan orogeny in the Carboniferous, south(east)-vergent decollement nappes, syntectonic flysch deposits, and granitoids are formed along with regional metamorphism. This is followed by a second stage in the Permian with north(west)-vergent thrusting, renewed granite formation, and metamorphism. The Variscan nappe pile is today exposed in a deeper level in the west or northwest than in the east or southeast.

Geochemical and geochronological data on Triassic volcanism of the Southern Alps of Lombardy (Italy): Genetic implications

Abstract: A widespread volcanism mainly consisting of pyroclastic products and lava flows is found in the Southern Alps of Lombardy. The volcanics are interbedded with Anisian-Ladinian carbonatic sequences and continental terrigenous or transitional deposits of Ladinian-Carnian age. The petrographic and geochemical data for this volcanism indicate a calc-alkaline affinity with characters similar to those of convergent continental margins. In this sector of the Alps the geological evidences show that in the middle Triassic general extensional movements were the dominant deformation event, and do not support the existence of a subduction zone during this period. The apparent contrast between the tectonic environment and the type of magmas erupted in the Anisian-Carnian is tentatively explained by partial melting during the early stage of rifting of an upper mantle deeply modified during the previous Hercynian orogenesis and contaminated by crustal material. This hypothesis is in agreement with the preliminary Sr isotopic ratios (0.705 and 0.709). K/Ar and Rb/Sr ages on biotites date the beginning of the volcanism at around 225 m.y.

A zone of mylonite and related ductile deformation beneath the alpujarride nappe complex, betic cordilleras, S. Spain

Abstract: A zone of mylonite is commonly developed beneath the Alpujarride nappe complex. The contact with the underlying Nevado-Filabride Complex is marked by a zone of calc mylonite, dolomitic breccia, iron-rich carbonate rocks, and marble. These lie on a thin zone of ultramylonite derived from Nevado-Filabride schist. Related ductile deformation decreases downwards, but may extend up to 400 m beneath the contact. This deformation produces a characteristic platy foliation, a strong elongation lineation, and a proto-mylonitic microstructure. Kinematic analysis of these rocks may help determine the direction of nappe transport.

The External Massifs, relics of Variscan basement in the Alps

Abstract: Chemical and structural data give new insight into the complex metamorphic evolution of crystalline basement of the Helvetic Realm (Central and Western Alps). The relics of pre-Carboniferous basement — the so called External Massifs — may be subdivided into an older basement unit with a younger cover, which together suffered the following metamorphic evolution from late Caledonian until Variscan times: These results confirm that the External Massifs have to be interpreted as pieces of a former continental crust with a metamorphic evolution known from the mid-European Variscan crystalline basement.

Geologische Vorgänge in den Alpen ab Obereozän im Spiegel vor allem der deutschen Molasse

Abstract: Die vorquartare Geschichte des Molassebeckens nordlich der Alpen last sich in 3 Grosabschnitte unterteilen, in deren Ablauf sich umrishaft die jeweils zugehorigen Entwicklungsstadien des aufsteigenden Gebirges widerspiegeln, die bisweilen umgekehrt auch von Ereignissen im Vorland beeinflust werden. Der 1. Abschnitt (Obereozan bis Aquitan/ Ober-Eger) ist von der in den Westalpen beginnenden Hebung sowie von Bewegungen der savischen Dislokationsphase gepragt, in besonderem Mase ferner an der Rupel/ChattGrenze von der grosten Meeresspiegelsenkung seit dem Kambrium. Im 2. Abschnitt (Burdigal/Eggenburg bis Unterpannon) verlagert sich die Hebungsaktivitat zu den Ostalpen, womit im Vorland die grose, E-W gerichtete Flusschuttung der Oberen Suswassermolasse ausgelost wird. In ihr verursacht die gewaltige Erderschutterung des Riesmeteoriten-Einschlags im hoheren Baden vermutlich die Flusverlegung der Enns, eines ihrer beiden Hauptzubringer, zum Grazer Becken und damit eine sich u. a. im Schwermineralbestand (als „A-Grenze“) abzeichnende Anderung der Materialzufuhr aus dem Gebirge. Im 3. Abschnitt (Unterpannon bis Pliozan) geht infolge weiteren Aufsteigens der Alpen samt Vorland bei gleichzeitiger Verlagerung des Hebungszentrums wieder zur Westschweiz die bisherige Akkumulation in Denudation uber, die von dem sich nun von Niederosterreich aus ins Molassebecken „hineinfressenden“ Donausystem besorgt wird.

Hauptdolomit — Sedimentary and paleogeographic models (Norian, Northern Calcareous Alps)

Abstract: In previous work, relationsships between carbonate petrographic features and geochemical parameters were used in the development of a sedimentary model for Hauptdolomit. It was found useful to categorize the various facies subtypes into eight main facies units which correspond to environments ranging from supratidal to subtidal.

Metamorphic an magmatic events in the Uweinat — Bir Safsaf Uplift (Western Desert/Egypt)

Abstract: The Uweinat — Bir Safsaf Uplift, Western Desert/Egypt, four episodes of deformation and related metamorphism and anatexis occurred until the final cratonisation during the Late Pan-African event was completed. From that time on, probably six independent (Table 4) magmatic episodes can be recognized up to the Quaternary. This anorogenic type of magmatism is mainly related to a fracture system which originated in the Late Precambrian as a result of intraplate block faulting. Periodical reactivation of these older fracture zones throughout the Phanerozoic gave way to the different types of plutonic and volcanic rock assemblages.

Permian deposits of the Southern Alps as product of initial alpidic taphrogenesis

Abstract: Sedimentological and morphotectonic investigations of Permian deposits between the Val Camonica and the Karawanken Mountains indicate the development of a complex rift-system which initiated the alpidic sedimentation phase The extensive distribution of regoliths and palaeosoils at the base of the Permian deposits demonstrate the existence of a consolidated and subsequently truncated crust The senile topography which prevailed at the beginning of the Permian had to be modified by fault movements to provide the erosional and transport energy required for the deposition of psephytes and other siliciclastica (scarp foot fans) The formation of syndepositional graben structures, diagnostic for an overall distentional regime, led to the development of three morphotectonic units Commencing in the early Permian with fissure volcanism, a central, northeasterly trending rift developed The western margin of it was modified by rift-parallel faulting the resulting trough serving as receptacle for lacustrine sediments The area to the east of the central rift was separated by a pronounced graben shoulder, the eastern perimeter of which supported a marine carbonate platform Rejuvenation of tectonism near the middle of the Permian established a new, east-southeast trending rift-branch and expelled the sea from the eastern basin The ensuing fluviatile regimes, draining mainly in southerly to south-westerly directions resulted in a general equalisation of the landscape In the late Permian, the eastern part of the area became inundated by a shallow, evaporitic sea, but fluviatile conditions prevailed in the west until the onset of the Triassic Current directions indicate a south-westerly outlet path for these systems and thus the existence of another, presumably marine base level in that direction

Zusammenhänge in der Strukturgenese des Rheinischen Schiefergehirges

Abstract: Ausgehend vom Mas der Inkohlung organischer Substanz in den Gesteinen des nordlichen Schiefergebirges einschlieslich der Eifel konnen nach der Bestimmung der Beziehungen Aussagen zur tektonischen Evolution und zur Palaogeothermie des betrachteten Gebietes getroffen werden. Es bestatigen sich fruhere Ansichten, das die Grossattel aus Bereichen verminderter Absenkungsgeschwindigkeit in der Geosynklinale mit gleichzeitig relativ hoheren geothermischen Gradienten hervorgehen. Obgleich Absenkung und Warmeflus derart miteinander verbunden scheinen, ist das in den Inkohlungsdaten abgebildete Warmefeld wahrscheinlich der Effekt einer Uberlagerung eines prakinematischen, durch Absenkungsdifferenzen mitbestimmten Warmefeldes mit einer wahrend der Heraushebung in der Geosynklinalfullung nordwarts wandernden Abkuhlfront. Alle im Kartenbild deutlichen Grosstrukturen des nordlichen Schiefergebirges sind auf ein kongruentes synsedimentares Absenkungsmuster im Verein mit einer — moglicherweise ebenfalls vom thermischen Regime beeinflusten — differentiellen Heraushebung zuruckzufuhren. Der eigentlichen Faltung kommt dabei nur die Rolle eines die vorhandenen Strukturen uberpragenden Faktors zu.

Zum Nachweis jurassisch-kretazischer Eingleitungen von Hallstätter Gesteinsmassen beiderseits des Salzach-Quertales (Salzburg)

Abstract: Beiderseits des Salzach-Quertales finden sich zahlreiche Hinweise, das im Tithon permotriadische Gesteinsmassen mit Hallstatter Fazies aus ihrem triadischen Becken (Vorriff) Sedimentationsraum heraus nordwarts in den Plattformbereich einglitten. Zu diesen synsedimentar in den tithonen Anteil der Oberalmer Schichten (Kimmeridge/Tithon/Berrias), einem Tiefseesediment, eingebrachten Massen konnen die Schollen der Hallstatter Zone

Anchimetamorphose im Anis und Ladin (Trias) der Nördlichen Kalkalpen zwischen Arlberg und Kaisergebirge — ihre Verbreitung und deren baugeschichtliche Bedeutung

Abstract: Im Anis/Ladin der Nordlichen Kalkalpen wurde zwischen Arlberg und Kaisergebirge aus ca. 50 sehr detailliert aufgenommenen Profilen von uber 2500 Proben der in Ameisensaure unlosliche (Silikat-)Ruckstand mineralogisch untersucht. Die in der Fraktion kleiner 2 μ enthaltenen Schichtsilikate bestehen weitgehend, einheitlich und vorwiegend aus dioktaedrischen Illiten, deren kristalliner Ordnungsgrad („Illit-Kristallinitat“) als wichtigstes Untersuchungsergebnis in zweierlei Hinsicht zunehmende Tendenz enthullt: 1. Der sudliche Teil der Lechtal-Decke ist im gesamten Untersuchungsbereich ausgezeichnet durch eine Zunahme der innerkristallinen Ordnung der Illit-Minerale vom stratigraphisch Hangenden zum stratigraphisch Liegenden der untersuchten Profile, ohne Rucksicht auf deren heutige Orientierung. Dieser Effekt mus daher bereits vor der Faltung bewirkt worden sein. 2. Im gesamten Arbeitsgebiet zeigt sich eine generelle Zunahme des Ordnungsgrades von Norden nach Suden, unabhangig von allen jetzt vorhandenen tektonischen Strukturen (Faltenbau und kalkalpine Teildecken). Dieser Effekt mus also junger sein als deren Ausbildung. Hierbei wird ein breiter Saum „anchimetamorpher“ Beeinflussung innerhalb des Sudteiles der Nordlichen Kalkalpen erkennbar, der im Bereich der Mieminger Berge und des Wettersteingebirges auserdem noch weit nach Norden (etwa bis Garmisch-Partenkirchen) ausbiegt.

Sediments and micronodules in the northern and central Peru Basin

Abstract: The mineralogy and composition of sediments and manganese micronodules from the northern and central sectors of the Peru Basin are discussed. Because of the proximity of the basin to the Carbonate Compensation Depth (C.C.D.), surface sediments vary between calcareous oozes and siliceous muds. Besides biogenic components clay minerals are important. By far the most abundant clay mineral is smectite which is thought to be of diagenetic origin. On a carbonate-free basis, the surface sediments are rather uniform in composition throughout the basin and are similar in composition to those of the equatorial Pacific. Sedimentation rates for the uppermost core sections are in the range of 3 to 5 mm/ 1000 yr. Micronodule compositions show significant variations related to the size class of the micronodules and the depth of occurrence within the sediment column. In general, the chemistry of the micronodules can be explained by the reductive mobilization of Mn within the sediment column and by oxic diagenetic reactions between ferromanganese hydroxides and biogenic opal. The dominant mineral phase is todorokite.

Slumpfolds and other early deformations in the early Cambrian of the Western and Central Antiatlas (Morocco)

Abstract: Most of the deformations at the base of the serie des calcaires inferieurs and the serie des calcaires superieurs (early Cambrian, Antiatlas) were caused by synsedimentary to early dislocations. Submarine slumpings are discernible in the centimeter to onehundred meter range; differences in density and diagenesis result in ball and pillow structures and mud diapirs in the shallow-water carbonates. Locally, these syngenetic structures are overprinted by later tectonic movements; in this case, a distinct separation of these different processes of development is difficult.

Zur Anchimetamorphose permo-skythischer Sedimentgesteine im westlichen Drauzug, Kärnten — Osttirol (Österreich)

Abstract: An 86 Proben permo-skythischer bis kretazischer Sedimentgesteine des westlichen Drauzuges wurden Metamorphosestudien vorgenommen. Es wurde die Illit-Kristallinitat (IK) ermittelt und zusatzlich an Kluftquarzen von 9 Lokalitaten auch die Gas- und Flussigkeitseinschlusse untersucht.

Sedimentological response to late Mesozoic subduction in the Penninic windows of the Eastern Alps

Abstract: Late Mesozoic subduction of Penninic oceanic lithosphere finds its response in the sedimentary record. The corresponding sediments are deposited in a deep-sea trench environment and are developed as distal, partly proximal flysches, containing breccias and olistolites, which are up to kilometer-sized (wildflysch). In the Tauern window this facies is represented by the Nordrahmen zone, which is the equivalent to the Matrei zone. It is proposed to apply the term “Matrei zone” to the entire zone. It forms the high parts of the Bundner Schiefer and Tauernflysch formation. The olistolites derive from the unstable Austroalpine continental margin (Lower Austroalpine).

Das Altpaläozoikum und Unterkarbon des Gurktaler Deckensystems (Ostalpen) und ihre paläogeographischen Beziehungen

Abstract: Die Schichtfolgen des Palaozoikums des Gurktaler Deckensystems (Ostalpen) lassen sich in zwei tektonische Einheiten untergliedern, die sich in ihrer Ausbildung unterscheiden: (1) Die tiefere, epimetamorphe Murauer Decke ist durch Schwarzschiefer, Kalkphyllite (vorwiegend Silur) und bis mehrere 100 m machtige Karbonatfolgen (vorwiegend Unterdevon) gekennzeichnet. (2) Die hohere, epi- bis anchimetamorphe Stolzalpendecke fuhrt basal (ober-)ordovizische und tiefsilurische vulkanogene Folgen. Das hohere Silur bis tiefere Unterdevon last drei laterale Faziesbereiche erkennen, wahrend das hohere Unterdevon bis Unterkarbon vorwiegend durch eine einheitlichere, pelagische Karbonatentwicklung charakterisiert ist. Die Auflosung der Gurktaler Decke in zwei tektonische Einheiten nach der Ausbildung des Altpalaozoikums und Unterkarbons ist auf das ubrige sudliche Oberostalpin ubertragbar. Das Palaozoikum der Stolzalpendecke zeigt Beziehungen zu den hoheren Decken des Oberostalpins (z. B. Norisches Deckensystem, Nordrand des Grazer Palaozoikums) und zu den westlichen Karnischen Alpen, die tiefere Murauer Decke zur Schockeldecke s. 1. innerhalb des Grazer Palaozoikums und zum mittelostalpinen Muralpenkristallin. Die Anordnung der vulkanogenen Formationen der hoheren oberostalpinen Decken last einen NE-SW-Trend erkennen. Das schwachmetamorphe ostalpine Altpalaozoikum wird auf Grund von basalen Kristallinkonglomeraten als epikontinentale, transgressive Serie auf einem praoberordovizisch gepragten Untergrund betrachtet.

Über die Beziehungen des „Cenomans“ zur Gosau in den Nördlichen Kalkalpen und ihre Auswirkungen auf die paläogeographischen und tektonischen Vorstellungen

Abstract: Die Beziehungen des „Cenomans“ der Nordlichen Kalkalpen zur Gosau betreffen die Stratigraphie und die Palaogeographie. Das ehemalige „Cenoman“ wird heute zu den Branderfleck-Schichten gestellt und hat aufgrund der Neuuntersuchung der Foraminiferenfauna eine stratigraphische Reichweite vom Untercenoman bis in das Untercampan. Anhand von funf ausgesuchten Profilteilen aus den Bayerischen Kalkalpen wird kurz die lithologische Entwicklung und die Biostratigraphie aufgezeigt. „Cenoman“ und Gosau uberlappen sich stratigraphisch. Eine Schichtlucke im Oberturon als Ausdruck der pragosauischen/mediterranen Faltungsphase gibt es nicht. Olistholithe in Flachwasser-Fazies aus olisthostromatischen Sedimenten werden von einer im Suden gelegenen Schwellenregion bezogen. Die Existenz dieser Oberaudorfer Schwelle ist fur den Zeitraum Cenoman bis Santon gesichert. Sie trennte ab dem Coniac die Branderfleck-Schichten im Norden von den altersgleichen Gosau-Sedimenten im Suden. Die basale Gosau des Unterinntals wurde insbesondere am Florianiberg bei Oberaudorf untersucht. Dabei fielen drei Typen von Unterkreide-Gerollen, vorwiegend in Urgon-Fazies, auf, die stratigraphisch in das Apt zu stellen sind. Die drei genannten Aspekte, Stratigraphie der Branderfleck-Schichten, Olistholithe in Flachwasser-Fazies von der Oberaudorfer Schwelle und die unterkretazischen Urgon-Gerolle der basalen Gosau, fuhrten zu neuen Vorstellungen uber die palaogeographische EntWicklung des mittleren Teils der Nordlichen Kalkalpen vom Barreme bis zum Santon. Es wird wahrscheinlich gemacht, das die kalkalpine Urgon-Schwelle (Barreme-Apt) auf dem sudlichen Bajuvarikum und/oder auf dem nordlichen Tirolikum gelegen ist und vom Barreme bis zum Priabon aufgrund der tektonischen Raumverengung allmahlich nach Norden gewandert ist. Dabei hat sie immer wieder Urgon-Gerolle geliefert (Dynamisches Modell). Der Nachweis luckenloser Sedimentation auf der Lechtal-Decke, insbesondere uber die Turon/Coniac-Grenze hinweg, nimmt dem bisher starksten Argument, das fur die pra gosauische/mediterrane Phase sprach, ganzlich seine Wirksamkeit. In der Kritik der Phasenlehre wird der Ablauf tektonischer Ereignisse im Kalkalpin zur Kreidezeit in FormStillescher Faltungsphasen abgelehnt. Es handelt sich vielmehr um kontinuierliche Langzeitvorgange, die sich vorwiegend unter Meeresbedeckung abgespielt haben.

Evidenzen für die Vergletscherung eines alpinen Bergeller Hochgebirges an der Grenze Oligozän/Miozän

Abstract: Aus fossilen Floren abgeleitete palaoklimatische und -okologische Daten, Gerollanalysen und Alters-, insbesondere Spaltspur-Daten aus der sudalpinen Molasse und vom Bergeller Pluton erlauben den Zusammenhang zwischen Vorland und alpinem Relief zu gewinnen. Die Zusammenfassung aller Daten und Evidenzen bringt uns zu folgender Vorstellung:

A gravity-derived model for the steinheim impact crater

Abstract: The gravity survey of the Steinheim impact crater comprises about 500 gravity stations resulting in aBouguer anomaly map of the crater and its surroundings. From this map aBouguer residual anomaly of the impact structure was deduced which shows considerable character. A central negative anomaly with an amplitude of about -2 mgal and a halfwidth of 3 km is surrounded by ring-like relative positive and negative anomalies which extend to a radial distance of about 5–6 km. The interpretation is based on nine radial profiles with close station spacing. Model calculations were performed suggesting the Steinheim crater to be much larger and of different formation than has been assumed. Based on the gravity interpretation, on a morphological analysis, and on additional geological and geophysical observations a model of the Steinheim crater and its development is proposed. The main characteristics are a 500–600 m deep primary excavation and a final, apparent, diameter of roughly 7 km, contrasting to an up to now favoured shallow excavation and a 3.5–4 km final diameter. The model considerations include mass and energy calculations and references to the Ries impact crater.

Zur Geologie des Thurntaler Quarzphyllits und des Altkristallins südlich des Tauernfensters (Ostalpen, Südtirol)

Abstract: Geologische und petrographische Untersuchungen im Thurntaler Quarzphyllit und im angrenzenden Altkristallin sudlich des Tauernfensters lassen einen mehrfachen Wechsel von Deformation und Kristallisation erkennen. Im gesamten Untersuchungsbereich waren vor allem Deformationen gefugepragend fur die Gesteine.

Mesozoic volcanics of western sicily

Abstract: The Mesozoic lavas and minor intrusions in the thrust sheets of western Sicily have the following characteristics: 1. The lavas in the Triassic Mufara Formation in the north were broken into fragments which rotated independently within the incompetent strata that enclose them. This behavior is characteristic of igneous rocks found within the more internal (northerly) thrust units. 2. The Jurassic lavas in the more external (southerly) units have consistent directions which agree with those of the Ammonitico Rosso limestones in the same zone and lie about 30° clockwise from those of coeval autochthonous formations in Tunisia.Schult's presumed Cretaceous directions from Custonaci on the north coast (similar to those found in the Cretaceous Scaglia Rossa at Terrasini to the east byChannel et al., 1980) are rotated still more (140°) with respect to those of the autochthonous Iblean platform of SE Sicily. These differences are believed to reflect rotation of the thrust sheets during tectonic transport in Cenozoic times, the internal units being the most strongly rotated. 3. All the igneous rocks are highly altered: generally the original mineralogy cannot be completely determined. Relative abundances of some of the less mobile elements (Ti, Sr, Y) suggest that they are intraplate basalts.

Paläomagnetische Untersuchungen im Schilfsandstein (Trias, Km2) Westeuropas

Abstract: Von insgesamt 46 beprobten Profilen aus dem Schilfsandstein (Trias, Km2) Westeuropas wurden bislang 41 Profile mit 343 Einheiten und 870 Handstucken mit 1897 Einzelkernen auf ihren palaomagnetischen Inhalt untersucht.