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A correlation of tectonic units of the Alpine-Carpathian-Dinaridic system of orogens, including the substrate of the Pannonian and Transylvanian basins, is presented in the form of a map. Combined with a series of crustal-scale cross sections this correlation of tectonic units yields a clearer picture of the three-dimensional architecture of this system of orogens that owes its considerable complexity to multiple overprinting of earlier by younger deformations.

Shallow-water limestones of presumed Late Cretaceous and Eocene age, interbedded with basaltic lavas, were described by earlier authors from São Nicolau in the northwestern part of the Cabo Verde archipelago. If confirmed, these ages would imply late Mesozoic shallow-marine and subaerial volcanic activity in the Cabo Verde archipelago, and document a geological history very different from that known so far from other Cabo Verde Islands, from which no subaerial volcanic activity before the mid-Cenozoic is known. Our re-investigation of the foraminiferal fauna indicates a Late Miocene age for the presumed Late Cretaceous and Eocene limestones. The hypothesis of a long-lived hot spot, active by the Early Cretaceous, and of a major island-building stage in the Cabo Verde Islands during this period, is therefore not supported by the present bio- or chronostratigraphic data.

The tectonic interpretation of basement structures in seismic reflection profiles from ocean-continent transitions (OCT) of magma-poor rifted margins is notoriously difficult due to the scarcity of borehole information. Low-angle intra-basement reflections are frequently interpreted as detachment faults, and in certain locations the drilled top of the basement is interpreted as exhumed detachment fault. The seismic expression of such detachment faults is, however, poorly understood. We address this problem by comparing synthetic seismic data from the Tasna OCT, an exposed remnant of a Tethyan margin, with seismic reflection data from Hobby High, a drilled basement high within the west Iberian margin. Both sites are widely considered as being representative of OCT zones. Their geological similarity and the complementary nature of the data enable us to perform a detailed investigation of the seismic structure and response of these OCT zones. This provides insights into the seismic imaging of OCT zones in general and the tectonic evolution of the associated detachment systems in particular. On the basis of the Tasna OCT models and their seismic responses we have identified some potential characteristics of intra- and top-basement detachments: (i) variable amplitudes and numerous diffractions from the top of exhumed subcontinental mantle, (ii) a continuous and strong reflection imaging the top of exhumed lower crustal rocks, and (iii) a weak and discontinuous reflection of inverse polarity representing a shallow intra-basement crust-mantle detachment. Similar features are consistently observed at geologically equivalent positions in the seismic data from Hobby High and may thus serve as guidelines for interpretation of seismic data from un-drilled OCT zones.

AbstractMesozoic deep-water sediments occurring on the island of Fuerteventura were deposited near the continent?ocean boundary adjacent to the African margin. During Tertiary times, they were uplifted and intruded by ultramafic, mafic and alkaline plutons and dykes and are now exposed as part of the ?Basal Complex? of the island. These sediments reflect more or less continuous hemipelagic and turbiditic deposition during most of Jurassic and Cretaceous times. Two ammonites, described in this paper, document a Valanginian to Hauterivian age for part of the Lower Cretaceous siliciclastic turbidites, and a latest Albian to early Cenomanian age for part of the Upper Cretaceous hemipelagic limestones.

Although of different age, the undeformed Cretaceous Iberia/Newfoundland margins and the relics of the Jurassic Briançonnais/Adriatic margins preserved in the Alps document a similar spatial and temporal evolution of rifting suggesting that the evolution of both pairs of margins was controlled by the same processes. Rifting appears to depend strongly on the thermal history of the lithosphere, which controls the rheology and consequently also the structural evolution of the margin. The tectonic evolution of non-volcanic margins appears to be distinctly different from that of volcanic ones.

A history of geodynamic evolution of the Mediterranean leading to the salinity crisis is outlined, based on the ‘desiccated deep-basin model’. An accurate portrayal of the crisis is presented, based on data from new drilling and studies of on-land geology.

Zusammenfassung Röntgendiffraktometrisch bestimmte Tonmineral-Assoziationen in den jurassisch-unterkretazischen hemipelagischen und pelagischen Sedimenten sowie in den Oberkreide-Flyschen des Lombardischen Beckens der Südalpen erlauben wichtige Rückschlüsse über tektonische und eventuell klimatische Änderungen in den Liefergebieten sowie, in etwas geringerem Maße, über Veränderungen während der Uberlagerungs-Diagenese.

The progressive lithification of Quaternary hardgrounds forming in the Hellenic Trench region of the eastern Mediterranean is documented by increasing 18O values and high-magnesium calcite contents, which reflect cold, penesaline waters. The presence of aragonite and dolomite in hardgrounds from the Strabo Trench, which are also enriched in 12C, indicates that the diagenetic solutions vary locally. The origin of this unusual mineralogy and carbon isotopic content could be explained by the upward migration of brines from the underlying Messinian evaporites and the subsurface oxidation of 12C enriched organic material. Shallow burial of the evaporites in the Strabo Trench, a region dominated by transcurrent motion, as opposed to deeper burial in the Matapan- and Poseidon Trench, regions dominated by subduction and thrusting motion, could be responsible for geochemical variations in the diagenetic solutions.

Zusammenfassung Überreste des Ligurisch-Piemontesischen Ozeans mit seiner ophiolitischen Unterlage sind in den südpenninischen Decken Graubündens (E-Schweiz) erhalten. Auf Grund einer Analyse der südpenninischen Stratigraphie und einem Vergleich mit Serien aus ophiolithführenden Decken der Westalpen und Apenninen interpretieren wir die südpenninischen Decken als Relikte eines ozeanischen Transform-Bruch-Systems. Diese Interpretation beruht auf drei Argumenten: (1) Die stark zerrissene Ophiolitabfolge ist von pelagischen Sedimenten des ?mittleren und oberen Jura überlagert, wobei diese sowohl mit Basalten als auch mit Serpentiniten in stratigraphischem Kontakt sind. Wir vergleichen die südpenninischen Serpentinite mit Serpentinit-Protrusionen entlang von ozeanischen Bruchzonen. (2) Ophiolith-Breccien (»Ophicalcite«), die entlang bestimmter Zonen innerhalb des Serpentinitmuttergesteins auftreten, sind mit Breccien, wie sie in heutigen Transform-Brüchen gefunden werden, vergleichbar. Tektonische und sedimentäre Prozesse waren an der Bildung dieser Breccien beteiligt. Serpentinite zerbrachen in tektonisch aktiven Zonen und die entstehenden Risse und Gräben wurden mit pelagischem Sediment und mit Kollapsbreccien gefüllt. Hydrothermale Prozesse überprägten viele der Ophicalcite. (3) In den oberjurassischen Radiolariten findet man wiederholt Einschaltungen von Konglomeraten, in denen Ophiolith-Komponenten dominieren, in denen aber auch Komponenten von granitischen Gesteinen und von Flachwasserkarbonaten (?Triasische Oolite) an verschiedenen Orten beigemischt sind. Daraus schließen wir auf eine enge Nachbarschaft von ozeanischer und kontinentaler Kruste im Bereich des südpenninischen Ozeans. Ähnlich wie heute im Golf von Kalifornien dürfte die mesozoische kontinentale Kruste entlang des Ligurisch-Piemontesischen Ozeans durch Bruchzonen segmentiert worden sein. Über dieses ausgeprägte Relief lagern sich in der unteren Kreide pelagische Kalke, Mergel und schwarze Kieselschiefer, die Hinweise auf die Ozeanographie der Tethys geben.

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Copyright of Geologische Rundschau is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)