MIDDLE TRIASSIC AMBER ASSOCIATED WITH VOLTZIALEAN CONIFERS FROM THE SOUTHERN ALPS OF ITALY

Amber from the Carnian succession of the Dolomites and Julian Alps (northeastern Italy) represents one of the most ancient and quantitatively substantial Triassic fossil resin records in the world. So far, the Carnian appeared to be the only Triassic stage with findings of amber remains. However, the recent reappraisal of historical collections of plant fossils led to the discovery of even older Triassic amber, found on a rock slab from the “Voltzia beds” of the Recoaro area (Anisian) and on a sample from the “Wengener Schichten” of Wengen/La Valle (Ladinian), respectively. Both specimens are associated with conifer shoots of Voltziales. To date, they are the oldest known Triassic fossil resins, demonstrating that the preservation of amber was not restricted to the sediments deposited during the Carnian as suggested before. These finds contribute to partially fill the gap in the amber record between the Carboniferous and Upper Triassic

Characteristics of a Triassic regional unconformity between the second and third shallow-marine depositional megasequences of the Karst Dinarides (Croatia)

Abstract Two depositional megasequences of the Karst Dinarides that record two different, emersion-separated, depositional periods are presented; the older lasted from the upper part of the Middle Permian to the Middle Triassic, and the younger one from the Late Triassic to the Late Cretaceous. Both megasequences are typified by shallow-water platform deposits; the earlier megasequence formed under epeiric carbonate/clastic platform conditions and the later one under isolated carbonate platform conditions. Significant geodynamic movements within the southern Tethys realm led to Middle Triassic tectonic uplift, i.e. to the emersion of the huge platform area where a regional unconformity between two platform megasequences was formed. Four types of terrestrial phase horizons are identified, each representing different subaerial conditions that existed during the long-lasting emersion. These are: a significant disconformity and related stratigraphic gap between the Upper Scythian and Lower Norian; a tuffaceous horizon between the Upper Anisian and Lower Norian; an Upper Ladinian-Upper Norian brecciated horizon; and an Upper Ladinian-Lower Norian claystone/bauxitic horizon. Due to the widespread diachronous transgression during the Norian, shallow-water platform sedimentation was restored over the entire emergent area, initiating a long-lasting isolated carbonate platform regime

Trijaska kopnena faza zabilježena na slijedu karbonatne platforme krških Dinarida (Hrvatska)

The Triassic carbonate platform succession of the Karst Dinarides was deposited at the southern Tethyan realm. The facies analysis and distant correlation suggests that a regional terrestrial phase occurred in that area during the Triassic. Due to its regional extent, this terrestrial phase has been viewed as a product of tectonically induced uplift of the huge platform area, causing an extensive emersion and distinct disruption in depositional regime when disconformity and/or various types of terrestrial depositional intervals were formed. Two geodynamic scenarios are presented; a) regional, contemporaneous tectonic uplift scenario; and b) diachronous and differential tectonic uplift scenario. During Norian, the uplifted, exposed platform area was flooded and covered by tidal flat-dominated shallow-water carbonates, marking the beginning of wide and long-lasting isolated platform regime.Trijaski karbonatni slijed Krških Dinarida istaložen je na prostranstvu južnog Tetisa. Facijesna analiza i prostorna korelacija tog slijeda naslaga upućuje na regionalnu kopnenu fazu koja je tijekom Trijasa zahvatila ovaj prostor. Svojim regionalnim pružanjem, ova kopnena faza se sagledava kao posljedica tektonski izazvanog izdizanja prostranog platformnog područja, a što je uzrokovalo izrazito okopnjavanje i izrazit prekid dotadašnjeg taložnog režima, čime su nastali taložni diskonformiteti i/ili različiti tipovi kopnenih taložnih slijedova. Predstavljena su dva geodinamska scenarija; a) scenarij regionalnog, istovremenog izdizanja prostranog platformnog područja; i b) scenarij vremenom i intenzitetom različitog izdizanja prostranog platformnog područja. Tijekom Norika, to dotad izdignuto i izloženo platformno područje bilo je preplavljeno i prekriveno plitkovodnim karbonatima plimne zone, označavajući početak prostranog i dugotrajnog taložnog režima izolirane karbonatne platforme

TANYSTROPHEUS (ARCHOSAUROMORPHA, PROLACERTIFORMES) REMAINS FROM THE TRIASSIC OF THE NORTHERN FRIULI (NE ITALY)

The first diagnostic remains of the large prolacertiform Tanystropheus are reported from northeastern Italy. They include a proximal caudal vertebra from the Middle Triassic of Aupa valley (Udine, Friuli) and a cervical vertebra from the Carnian of Fusea (Udine). The cervical vertebra represents the first record of Tanystropheus in the Carnian and is the geologically youngest occurrence other than the Norian T. fossai. Tanystropheus lived along the coasts of the northwestern Tethys during the Late Triassic while it disappeared in Central Europe where continental environments were prevailing.&nbsp

UPPER TRIASSIC AMBER FROM THE DOLOMITES (NORTHERN ITALY).A PALEOCLIMATIC INDICATOR?

Amber in Triassic deposits in the Dolomites is demonstrated for the first time. The amber-bearing deposits belong to the middle part of the Dürrenstein Formation, referred to uppermost Julian (Lower Carnian, about 225 My). Chemico-physical features of amber, which occurs as small yellow to reddish droplets, have been determined. Infrared (IR) spectroscopy shows typical bands of fossil resins; the "fingerprint" region of the spectrum presents a unique pattern that cannot be referred to any other known fossil resin. Palynological investigation of amber-bearing layers shows a large prevalence of bisaccates and circumpolles. Particularly, the taeniate bisaccates are frequent (41%) and suggest a correlation with the amber-producing species. Amber production and preservation is possibly related to a humid climatic event.&nbsp

Update of ichnofaunal units and link with footprint biochrons in the late Palaeozoic to early Mesozoic of the Southern Alps: towards a better correlation with the marine realm

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Demise of Carnian platforms: large scale geometries and mechanisms of precipitation

During the Late Triassic, a climate change known as the Carnian Pluvial Event (CPE) resulted in a major crisis for carbonate producers. In the western Tethys, the change in carbonate production led to a dramatic modification of depositional geometries. The steep clinoforms of the high relief pre-crisis carbonate platforms were replaced by low angle ramp geometries. A quantitative three dimensional modeling of the geometry of sedimentary bodies in the Cortina d'Ampezzo area (North-eastern Italy) formed before, during and after the Carnian crisis, coupled with facies analysis, was performed in order to investigate in detail how the changes in shallow water carbonate precipitation influenced the depositional geometries of carbonate platforms. Facies and depositional geometries suggest that after the demise of high-relief, microbial dominated carbonate platforms, a phase of intermediate sedimentation took place, in which microbial carbonate mounds and loose carbonate and terrigenous sediments coexisted. The subsequent evolution to a ramp is characterized by the onset of a tide-dominated environment. In the study area, the sedimentary succession developed in a marine strait connecting two small basins. Both ebb and flood paleocurrents are documented and their directions are in agreement with the strait orientation, as inferred from the paleogeographic position of relict high-relief carbonate platforms. Facies and sedimentary structures related to variations in the hydraulic regime have been observed, including planar cross stratification, herringbone cross stratification, flaser to wavy to lenticular bedding and cyclical alternations of mainly oolitic-siliciclastic vs. mainly bioclastic-muddy laminae. The peculiarity of this tidal system is that, differently from all other known cases, it did not develop in a tectonically confined submarine graben or canyon, but in a marine passage between relict high-relief carbonate platforms. Sedimentary facies analysis, coupled with geological three dimensional modeling, led also to constrain the sequence stratigraphy of this complex stratigraphic interval, in which the eustatic and climatic signals can be disentangled. The climate change predates the sea-level drop and caused the demise of the microbial-dominated high-relief carbonate platforms. A surface similar to a drowning unconformity was thus generated, even though a transgression was not taking place. Only small isolated microbial carbonate mounds survived the crisis of high-relief platforms. The complete disappearance of microbial carbonates (i.e. mounds) and the definitive switch of the shallow water carbonates to loose-sediment dominated ramps coincides with a subsequent sea-level drop. Thus the demise of the Upper Triassic microbial dominated high-relief platforms of the Dolomites can be interpreted as a two step process: at first a climatic event killed the km-scale high-relief platforms; later a drop in sea level led to the definitive disappearance of the microbial carbonates

AMBER DROPLETS IN THE SOUTHERN ALPS (NE ITALY): A LINK BETWEEN THEIR OCCURRENCES AND MAIN HUMID EPISODES IN THE TRIASSIC

The Anisian amber from the “Voltzia beds” of the Recoaro area, produced by Voltzia recubariensis, represents the most ancient Triassic amber known so far. The discovery of amber in the Anisian localities of Kühwiesenkopf/Monte Prà della Vacca and Piz da Peres, in the Dolomites area, fills a gap in the amber fossil record and gives an important contribution to the knowledge of Triassic amber. The finding of amber droplets, both dispersed in the sediment and anatomically connected to shoot fragments of V. recubariensis, demonstrates that during the Anisian this species was a major resin-producer and that the favorable conditions for the preservation of resin and plant remains were present at regional scale. The contribution of Voltziales to Middle Triassic resin production in Northern Italy is also testified by the Ladinian amber from the “Wengener Schichten” of Wengen/La Valle, produced by Voltzia ladinica, whereas the Late Triassic amber was mainly produced by cheirolepidiaceous conifers. The finding of organic body trapped in the amber of Kühwiesenkopf/Monte Prà dalla Vacca is noteworthy, although difficult to interpret, and shows once again its capability to entrap and preserve witnesses of past life. Moreover, the correspondence between the Triassic amber occurrences and regional/global scale humid shifts, suggests a cause-and-effect relationship, in which the rise of amber production/preservation potential is related to climate/environmental changes, particularly in marginal marine/costal environments

Interpreting Early Triassic (Smithian) sea-level change and climate using sequence stratigraphy and oxygen isotopes of conodont apatite

The Early Triassic is conventionally interpreted to have a warm and ice-free climate. During this time, three globally recognized depositional sequences developed in response to ~My-scale sea-level changes. The Lower Triassic Lower Thaynes Formation records the Smithian (2nd sea-level cycle in the Early Triassic) in the western United States (Confusion Range and Weber Canyon, Utah). The Smithian portion of the Mikin Formation records an approximately time-equivalent sea-level cycle in northern India (Guling, Himachal Pradesh). The maximum flooding zone combined with existing age-diagnostic biostratigraphy allows for correlation between two sections in the western United States and one section in northern India suggesting the Smithian My-scale sea-level change was likely eustatic. Samples were collected for oxygen isotopic analyses of conodont apatite from the two field locations (in Utah) in a sequence stratigraphic framework to better understand the Smithian paleoclimate. Due to an up to ~1.5 ° disparity of values between the two locations, additional conodont elements were analyzed from the Guling, Himachal Pradesh, northern India, Bear Lake, southern Idaho, Wapiti Lake area in eastern British Columbia, Canada, and Sverdrup Basin in the Canadian Arctic. Conodont Alteration Index or CAI (a measure of post-burial thermal alteration based on color) was estimated for each of the locations listed above and range from 1.5 for Wapiti Lake and the Confusion Range to 5 for Guling. In addition, SEM images were taken to identify potential physical alteration of the conodonts for the Confusion Range (smooth surface with no signs of alteration), Weber Canyon (pitted surface with signs of potential alteration), and Guling (visibly the most pitted surface with signs of potential dissolution). The δ18O values for Weber Canyon range from ~14.4 to 15.8 °, the Confusion Range from ~16 to 16.9 °, northern India from ~15.8 to 16.5 °, Wapiti Lake from ~ 17.2 and 17.6 °, Sverdrup Basin range from ~14.5 and 14.8 °, and the Bear Lake value was ~ 16.5 °. Conodonts with a CAI of ï‚£ 3 or lower produced δ18O values that most likely reflect the primary Smithian ocean isotopic values. Assuming an ice-free ocean value of -1 °, sea-surface temperatures were calculated as ~35 to 38 ï‚°C for the paleotropical and ~32 to 34 ï‚°C for the paleosubtropical regions, which make sense given their latitudinal position. Warm ocean currents in the neo-Tethys Sea can potentially explain this discrepancy. All six locations indicate that the Smithian ocean was significantly warmer than the present ocean, and instead, most resemble the extreme greenhouse sea-surface temperatures calculated for mid- to late Cretaceous