V. Karakitsios

A global event with a regional character: the Early Toarcian Oceanic Anoxic Event in the Pindos Ocean (northern Peloponnese, Greece)

The Early Toarcian (Early Jurassic, c. 183 Ma) was characterized by an Oceanic Anoxic Event (T-OAE), primarily identified by the presence of globally distributed approximately coeval black organic-rich shales. This event corresponded with relatively high marine temperatures, mass extinction, and both positive and negative carbon-isotope excursions. Because most studies of the T-OAE have taken place in northern European and Tethyan palaeogeographic domains, there is considerable controversy as to the regional or global character of this event. Here, we present the first high-resolution integrated chemostratigraphic (carbonate, organic carbon, delta(13)C(carb), delta(13)C(org)) and biostratigraphic (calcareous nannofossil) records from the Kastelli Pelites cropping out in the Pindos Zone, western Greece. During the Mesozoic, the Pindos Zone was a deep-sea ocean-margin basin, which formed in mid-Triassic times along the northeast passive margin of Apulia. In two sections through the Kastelli Pelites, the chemostratigraphic and biostratigraphic (nannofossil) signatures of the most organic-rich facies are identified as correlative with the Lower Toarcian, tenuicostatum/polymorphum-falciferum/serpentinum/levisoni ammonite zones, indicating that these sediments record the T-OAE. Both sections also display the characteristic negative carbon-isotope excursion in organic matter and carbonate. This occurrence reinforces the global significance of the Early Toarcian Oceanic Anoxic Event.

Sedimentological study of the triassic solution-collapse Breccias of the Ionian zone (NW Greece)

The Triassic Breccias of the Ionian zone are typical evaporite dissolution collapse breccias. Several features indicate the pre-existence of evaporites, while alternation of dolomites and evaporites consist a very common association in the subsurface.Brecciation took place in two principal brecciation stages. The first brecciation stage started soon after deposition, during a period of subaerial exposure due to periodic seasonal desiccation and small-scale meteoric removal of intrastratal evaporites. During this stage, the carbonate beds suffered in-situ breakage and carbonate mud infiltrated into fractures.Shortly after, a major brecciation event occurred, that affected the still non-well lithified carbonate fragments, due to progressive dissolution of evaporites by meteoric water. Carbonate mud continues to be infiltrated in-between the breccia fragments. In the same time, intensive calichification processes were responsible for further brecciation and reworking of the brecciated carbonate beds locally sediments, testifying a period of temporary regional emergence (paleosoil).The breccia matrix is characterized by microbreccioid appearance, resulting from internal brecciation of the coarser clasts. Due to early calichification, the matrix becomes enriched in oxidized clays and by pronounced calichification tends to assimilate the breccia clasts, being gradually transformed into a calcrete with floating texture.Clasts microfacies types include phytoclasts with strongly impregnated by Fe-oxides laminae (laminar calcrete), carbonized plant tissue, lime and dolomitic mudstones with evidence of former evaporites (dolomite/calcite pseudomorphs after gypsum and/or void-filling anhydrite cement, molds after evaporite nodules, euhedral quartz crystals etc.), carbonate fragments pseudomorphic after evaporites, pelsparites/ intrasparites, recrystallized dolomites and dedolomites.The predominance of shallow intertidal to supratidal carbonate fragments, indicates that the strata that gave birth to the breccia, formed in a very shallow, restricted, hypersaline, lagoonal setting, evolved into sabkha sequences in the frame of a lowstand episode. Sedimentation of dolomite and evaporite is considered that has taken place during arid periods, while meteoric water influx during the wetter intervals. During that lowstand episode, that resulted in a hiatus interval, the breccias have suffered intensive calichification. Circulating pore-fluid brines resulting from evaporation, provoked syngenetic to early diagenetic dolomitization of muds, by increase of molar Mg/Ca ratio and provided ions for evaporite nodules/crystal growth.Post-Pliocene to Recent subaerial exposure of the carbonate breccias, led to intensive soil-forming processes, active till today, that accentuated the brecciated appearance of the formation. These processes are responsible for the formation of porous carbonate breccias, the so-called “rauhwackes”.

USING IDIOBLASTS TO GROUP LAURINOXYLON SPECIES: CASE STUDY FROM THE OLIGO-MIOCENE OF EUROPE

Several specimens of Lauraceae fossil wood from the Cenozoic of Greece (southern part of Lesbos), the Czech Republic (Kadaň-Zadni Vrch Hill and Jachymov), and Hungary (Ipolytarnoc) were studied. When considering whether they belonged to the speciose fossil wood genus Laurinoxylon, we reviewed the literature and data from InsideWood on fossil and modern woods. As a result, we propose criteria for excluding a fossil Lauraceae wood from Laurinoxylon and list the species that should be excluded from this genus. The criteria (filters) proposed to exclude a genus from having relationships with Laurinoxylon are: A. Axial parenchyma features: A1. Marginal axial parenchyma, A2. Aliform to aliform-confluent paratracheal parenchyma. B. Ray features: B1. Rays higher than 1 mm, B2. Exclusively homocellular rays, B3. Rays more than 5 cells wide, B4. Rays storied. C. Porosity features: Ring-porous. D. Idioblasts: Absence of idioblasts. Based on the distribution of idioblasts, we recognize four groups in Laurinoxylon (Type 1 - with idioblasts associated only with ray parenchyma cells, Type 2a - with idioblasts associated with both ray and axial parenchyma, Type 2b - with idioblasts associated both with rays and present among the fibres, and Type 3 - with idioblasts associated with ray and axial parenchyma and also among the fibres) and list the extant genera with features of those groups. Such grouping helps with interpreting the relationships of fossil lauraceous woods with extant genera. We discuss the Oligocene–Miocene European species that belong to these Laurinoxylon groups, noting that some warrant reassignment to different genera or even families. Future studies are needed to determine whether new genera should be established to accommodate these species. We propose the new combination Cinnamomoxylon variabile (Prive-Gill & Pelletier) Mantzouka, Karakitsios, Sakala & Wheeler.