The chronostratigraphy of Coniacian–Maastrichtian platform carbonates exposed on the island of Brač and the adjacent mainland has been revised, based on numerical ages derived from strontium-isotope ...stratigraphy (SIS) of low-Mg calcite of rudist shells. The Dol intra-platform basin formed during the mid-Coniacian–early Santonian. The base of the prograding Pučišća Formation is of mid-Santonian age (84.9
Ma) in the southeast, and late Middle Campanian (77.3
Ma) in the northwest of the island, indicating a progradation rate of the platform margin of ca. 2.5
km/myr. Subaerial exposure of the platform occurred during the latest Middle Campanian and is coeval with a major drop in sea level reported from the Boreal Realm, North America, and the southern Tethyan margin. The base of the Sumartin Formation is revised here to the earliest Late Campanian (ca. 75
Ma). At its top, the formation contains rudist-bearing limestones of latest Maastrichtian age (65.4–65.0
Ma). The exact position of the K/T boundary cannot be drawn due to the lack of material suitable for SIS, and to the absence of diagnostic fossils in restricted innermost-platform deposits of the Liburnian Formation, which follows conformably over the rudist-bearing Sumartin Formation.
Based on the revised chronostratigraphy of platform evolution, and particularly on the numerical ages that constrain the progradation of the Pučišća Formation, the stratigraphic ranges of characteristic Tethyan rudist bivalves and benthic foraminifers are re-evaluated.
The central part of the Dinarides, unlike the northwestern and southeastern Dinarides, shows a consistent pattern in the distribution of the large tectonostratigraphic units. From southwest (Apulia) ...to northeast, the following five main units originating in different parts of the Mesozoic Tethys, can be distinguished: (1) Adriatic–Dinaridic carbonate platform formations; (2) carbonate–clastic units (`flysch bosniaque') of the passive continental margin; (3) ophiolite-bearing formations of the Dinaridic Ophiolite Zone, also containing radiolarites, greywackes and shales, including mélange formations, and overstepped Late Jurassic to Cretaceous cover sequences; (4) active continental margin units represented by Upper Cretaceous–Palaeogene trench sediments with blueschists, tectonized ophiolite mélange, Alpine medium-pressure metamorphic rocks originated from Upper Cretaceous–Palaeogene sediments, and Alpine synkinematic granitoids; (5) a nappe consisting of allochthonous Palaeozoic–Triassic formations which is thrust onto the ophiolites and genetically related sedimentary formations. The frontal parts of this nappe directly overlie the northeastern margin of the Adriatic–Dinaridic carbonate platform, i.e. the External Dinarides.
The evolution of the Central Dinarides was controlled by a sequence of tectonic events which took place within the Alpine cycle: (1) Rifting processes lasting some 40–50 Ma which started in the Late Permian and ended in the Norian. (2) Opening of the oceanic Dinaridic Tethys commenced in the Late Triassic and persisted for some 70–80 Ma until the end of the Jurassic. (3) Subduction processes and emplacement of ophiolites started in Late Jurassic–Early Cretaceous times; during the closing phase of the `Dinaridic Ocean' (or Dinaridic Tethys) the Palaeozoic–Triassic nappe was emplaced on the ophiolites. The thrusting was accompanied by Alpine metamorphism (120–100 Ma). (4) The main Alpine deformational event and medium-pressure metamorphism with synkinematic granite plutonism took place in Late Eocene–Early Oligocene times when the ophiolite and Palaeozoic–Triassic nappes were emplaced on the Adriatic–Dinaridic carbonate platform which, at the same time, was deformed resulting in the development of the External Dinarides fold-and-thrust belt.
Upper Cretaceous carbonate deposits of Olib and Ist islands are characteristic of peritidal sediments. They consist of shallow subtidal deposits alternating with intertidal laminites ...(shallowing-upward cycles). Subtidal beds with micritic matrix predominate over peritidal sediments. Determination of the micro- and macrofauna revealed two distinctive assemblages: one of Middle to Upper Cenomanian and the other of Upper Turonian to Lower Santonian age. The relatively high proportion of subtidal over intertidal sediments (subtidal/intertidal ratio 2.72) indicates that the Middle to Upper Cenomanian beds were deposited during a fall in the third order relative sea-level curve (late HST to LST). Sediments of the next carbonate sequence (Upper Turonian to Lower Santonian) with a higher proportion of the subtidal over intertidal sediments (subtidal/intertidal ratio 4.57) indicate deposition during relative sea-level rise (TST) and highstand (HST). Senonian limestones are overlain by sediments of Lower Lutetian age.
On the southwestern slope of Mt. Svilaja a Triassic sequence is exposed. It is composed of Lower Triassic carbonate siliciclastic shelf beds that are unconformably overlain by Anisian breccia. The ...overlying pelagic Anisian and Ladinian strata with pyroclastic rockscan be interpreted as a result of rift tectonics of Adria micro-plate. A 500 m thick sequence is capped by an emersion surface by karstification and terrigenous sediments including conglomerate as a result of Late Triassic transgression and marking the lower boundaryof a new, Late Mesozoic, megasequence of the External Dinarides.By means of conodont study, in the lowermost part of the studied Mesozoic sequence, a Lower Triassic shallow-water conodont fauna yielding Pachycladina obliqua apparatus was recorded. Pelagic limestone beds overlying the »Otarnik breccia« are marked byconodont elements of the Anisian constricta Zone. The Ladinian interval is characterized (from bottom to top): trammeri A. Z., hungaricus A. Z. and mungoensis A. Z. The uppermost part of the section below the emersion surface is identified by Pseudofurnishiusmurchianus, indicating the Upper Ladinian-Lower Carnian murchianus Zone.
A Middle Miocene oil source rock has been identified by geochemicallogging of exploration wells in the Eastern Drava depression (EDD) and in the Slavonija-Srijem depression (SSD) at the south-east ...margin of the Pannonian Basin, Croatia. The source rock contains Type II to II/III kerogen and reaches early maturity stage at depths of about 2400 m. The Mesozoic sequences were found either to be absent or to be poor in organic matter within the analysed wells.According to C27-C28-C29 sterane and C27-C28-C29 monoaromaticsteroid distributions, gamacerane indices, C35 homohopane indicesand presence of C30 steranrs, the EDD and SSD oils wrre generatedfrom the same marine source rock. The distribution of homohopanesand high Ni/(Ni + V) porphyrin ratios indicates that the related sourcerock was deposited under suboxic conditions. The oils appear to havebeen generated from the source rock during the early to middle stagesof maturity. The oils are waxy, with pour points up to 30°C and sulphurcontents not exceeding 0.7%.
The island of Brač is a small part of the large Adriatic–Dinaridic carbonate platform, mainly built up of Upper Cretaceous and, to a lesser extent, Palaeogene deposits. The Pučišća Formation ...(Campanian) is one of the six lithostratigraphic units of the Upper Cretaceous succession (the Brač Group) which includes carbonate deposits ranging in age from the Mid Cenomanian to Maastrichtian. The Pučišća Formation contains three superpositional-lateral subunits: the Brač Marble, the Rasotica, and the Lovrečina members, which comprise seven microfacies types (MF) of foraminifera-bearing limestones based on analysis of larger benthic foraminiferal assemblages and microfacies features. MF-types range from assemblages dominated by hyaline foraminifera (the Brač Marble Member, late transgressive systems tract, TST) to assemblages dominated by various taxa of imperforate foraminifera (the Rasotica and Lovrečina members, highstand systems tract, HST). The assemblages of benthic hyaline and imperforate foraminifera and microfacies are used for interpretation of palaeoenvironmental features of the Pučišća Formation. Some of the larger benthic foraminiferal species from the Pučišća Formation have enabled new morphological observations to be made.
The recently discovered Tilovica breccias in Central Dalmatia are of submarine origin and assigned to a Paleocene age by means of smaller benthic and planktonic foraminifera found either in pelagic ...interbeds or in the matrix. The breccias define a "trough" produced by Cretaceous tectonics and submerged by the global sea-level rise. This provides a new insight into the evolution of the External Dinarides (Croatia) and suggests a new paleogeographic interpretation of the region.
