scholarly journals PLANKTON BIOSTRATIGRAPHY AND PALEOCLIMATIC IMPLICATIONS OF AN EARLY LATE MIOCENE SEQUENCE OF LEVKAS ISLAND, IONIAN SEA, GREECE

2017 ◽  
Vol 43 (2) ◽  
pp. 568
Author(s):  
A. Antonarakou
Keyword(s):  
Regional Climate ◽  
Foreland Basin ◽  
Time Interval ◽  
Global Changes ◽  
Distributional Pattern ◽  
Ionian Sea ◽  
Tectonically Active ◽  
Cooling Trend ◽  
Warm Temperate ◽  
Early Late

Planktonic foraminiferal biostratigraphy is carried out in an Early Tortonian tectonically active setting, located in the Pre-Apulian Foreland Basin in Levkas Island. The studied section (Manassi section) is composed of hemipelagic silty clays and turbidite sandstones, reflecting sedimentation as a result of thrust activity. The distributional pattern of biostratigraphical significant species suggests that the Manassi section has been deposited during the time interval that Globigerinoides obliquus occurs regularly, the neogloboquadriniids are present in low percentages and Paragloborotalia siakensis is continuously present. The correlation with astronomical tuned sections allowed dating the studied section as ranging between 11.54Ma to 11.2Ma, having a lower Tortonian age, above the Serravallian/Tortonian boundary (Paragloborotalia siakensis planktonic foraminiferal zone). On the basis of the obtained palaeoclimatic curve, a series of palaeoclimatic events are recognized. The faunal composition suggests a cooling trend in the lower part which has been correlated with the Mi5 event. This cooling is followed by a warm-temperate phase, punctuated by several negative peaks in the palaeoclimatic curve. The palaeoclimatic evolution of the study area generally corresponds to the global palaeoclimatic trend with some subtle differences, supporting that the regional climate of this area was not merely controlled by global changes in climate.

scholarly journals PALEOBATHYMETRIC EVOLUTION OF THE EARLY LATE MIOCENE DEPOSITS OF THE PRE-APULIAN ZONE, LEVKAS ISLAND, IONIAN SEA

2018 ◽  
Vol 40 (1) ◽  
pp. 39 ◽  
Author(s):  
H. Drinia ◽  
A. Antonarakou ◽  
G. Kontakiotis ◽  
N. Tsaparas ◽  
M. Segou ◽  
...  
Keyword(s):  
Late Miocene ◽  
Foreland Basin ◽  
Tectonic Activity ◽  
Turbidity Currents ◽  
Ionian Sea ◽  
Foraminiferal Assemblage ◽  
External Domain ◽  
Benthic Foraminiferal Assemblage ◽  
Early Late

The Manassi section in Levkas Island belongs to the Pre-Apulian (Paxos) zone, the most external domain of the Hellenic realm. Its Early Tortonian sediments contain a rich foraminiferal fauna dominated, in numbers of individuals, by planktic species. Its benthic foraminiferal assemblage is characterized by a high number of taxa, with low numbers of individuals. Their study provides a basis for interpreting the paleobathymetry of the basin.The Manassi section represents deposition in upper to lower bathyal depths, during a period of intense tectonic activity. Downslope transport of fauna by turbidity currents partly overprints the signal of paleobathymetrically-diagnostic foraminifera distribution. The recognition of allochthonous taxa is used, together with %P, to identify turbidite beds intercalated with in-situ marly sediments. The micropaleontological and paleobathymetrical analyses of the studied sediments indicate that these correspond to distal atypical flysch deposited in the foredeep depozone of the most external domain (Pre-Apulian zone) of the Hellenide foreland basin.

Dating lacustrine carbonate strata with detrital zircon U-Pb geochronology

Geology ◽  
2020 ◽  
Author(s):  
Emily S. Finzel ◽  
Justin A. Rosenblume
Keyword(s):  
Detrital Zircon ◽  
Relative Proportion ◽  
Foreland Basin ◽  
Depositional Environments ◽  
Detrital Zircons ◽  
Sediment Flux ◽  
Coarse Grained ◽  
Southwestern Montana ◽  
Tectonically Active ◽  
Lacustrine Carbonate

Carbonate lacustrine strata in nonmarine systems hold great potential for refining depositional ages through U-Pb dating of detrital zircons. The low clastic sediment flux in carbonate depositional environments may increase the relative proportion of zircons deposited by volcanic air fall, potentially increasing the chances of observing detrital ages near the true depositional age. We present U-Pb geochronology of detrital zircons from lacustrine carbonate strata that provides proof of concept for the effectiveness of both acid-digestion recovery and resolving depositional ages of nonmarine strata. Samples were collected from Early Cretaceous foreland basin fluvial sandstone and lacustrine carbonate in southwestern Montana (USA). Late Aptian–early Albian (ca. 115–110 Ma) maximum depositional ages young upsection and agree with biostratigraphic ages. Lacustrine carbonate is an important component in many types of tectonic basins, and application of detrital zircon U-Pb geochronology holds considerable potential for dating critical chemical and climatic events recorded in their stratigraphy. It could also reveal new information for the persistent question about whether the stratigraphic record is dominated by longer periods of background fine-grained sedimentation versus short-duration coarse-grained events. In tectonically active basins, lacustrine carbonates may be valuable for dating the beginning of tectonic subsidence, especially during periods of finer-grained deposition dominated by mudrocks and carbonates.

Taconian mélanges in the parautochthonous zone of the Quebec Appalachians revisited: implications for foreland basin and thrust belt evolution

2004 ◽  
Vol 41 (12) ◽  
pp. 1473-1490 ◽  
Author(s):  
F -A Comeau ◽  
D Kirkwood ◽  
M Malo ◽  
E Asselin ◽  
R Bertrand
Keyword(s):  
Foreland Basin ◽  
Late Ordovician ◽  
Thrust Faults ◽  
Thrust Belt ◽  
Thrust Sheet ◽  
Utica Shale ◽  
Thermal Maturation ◽  
Early Late

In the Quebec Appalachians, disruption, imbrication, and thrusting of the Taconian foreland basin sequence are responsible for the development of chaotic units within the turbiditic sequence of the Caradocian Sainte-Rosalie Group, the main lithologic assemblage of the parautochthonous zone. These chaotic units have been termed olistostromes or tectonosomes on the basis of field criteria and following Pini's (1999) classification. Olistostromal units containing blocks of the middle mudstone (Utica Shale) and upper turbidite units (Ste-Rosalie Group) of the foreland basin and spanning the Caradocian N. gracilis, C. americanus, O. ruedemanni, and C. spiniferus graptolite zones were deposited and incorporated into the Sainte-Rosalie Group. Disruption of more competent beds of the flyschic sequence and fault stacking and slicing of older rock units occurred along major thrust faults and now form structurally aligned corridors or tectonosomes. Graptolites and new chitinozoan data from both olistostromes and tectonosomes indicate older ages (early Late Ordovician) than the flysch units of Sainte-Rosalie Group (mid Late Ordovocian). Lithological, stratigraphic, and structural criteria indicate that tectonosome slices are imbricated foreland basin rocks that are correlative to the Black River, Trenton, Utica, Sainte-Rosalie, and Lorraine groups of the Laurentian platform. Thermal maturation data indicates that disruption of the autochthonous sequence, and folding and thrusting of the entire foreland basin sequence, must have occurred shortly after their deposition. Contrary to what had been suggested, blocks in the olistostromes and tectonosomes were not derived from the allochthonous Chaudière thrust sheet, even though it presently marks the southern contact with the parautochthonous zone. Imbrication of the foreland basin sequence must have occurred before emplacement of the Chaudière thrust sheet.

scholarly journals Megabeds in Istrian Flysch as markers of synsedimentary tectonics within the Dinaric foredeep (Croatia)

2021 ◽  
Vol 74 (2) ◽  
Author(s):  
Krešimir Petrinjak ◽  
◽  
Marko Budić ◽  
Stanislav Bergant ◽  
Tvrtko Korbar ◽  
...  
Keyword(s):  
Foreland Basin ◽  
Division I ◽  
Synsedimentary Tectonics ◽  
Sedimentary Evolution ◽  
The Matrix ◽  
Tectonically Active ◽  
Division Ii ◽  
Fault Scarps ◽  
Steep Slopes ◽  
Different Parts

Istrian Flysch was deposited during the Eocene in the Dinaric foredeep and is composed of hemipelagic marls and various gravity flow deposits. The latter are predominantly 5-40 cm thick turbidites, developed mostly as laminated and cross-rippled sandstone beds (Tb-e, Tc-e and Td-e Bouma sequences). In addition to the turbidites, there are deposits characterized by a significant thickness, occasionally more than 10 m, described as complex (bipartite) megabeds. The megabeds are composed of debrites in the lower part (Division I), and high-density turbidites in the upper part (Division II). The distinct clast composition of each megabed indicates that the lithoclasts were derived from tectonically active slopes and fault scarps along which collapses of the different parts of the Cretaceous to Palaeogene neritic carbonate succession, (that underlie the Flysch), occurred. The Division II deposits are well cemented, normally graded calcirudite/calcarenites composed mostly of orthophragminids, nummulitids, and red algae, originating from outer ramp environments. Redeposited marl, observed in the matrix of the debrites and as intraclasts in some megabeds, implies that the collapses along the synsedimentary fault scarps and steep slopes also occurred within the foredeep itself, during the rapid tectono-sedimentary evolution of the Dinaric foreland basin.

scholarly journals Modern calibration of <i>Poa flabellata</i> (Tussac grass) as a new paleoclimate proxy in the South Atlantic

2020 ◽  
Author(s):  
Dulcinea V. Groff ◽  
David G. Williams ◽  
Jacquelyn L. Gill
Keyword(s):  
Relative Humidity ◽  
Isotopic Composition ◽  
Isotope Composition ◽  
Regional Climate ◽  
South Atlantic ◽  
Falkland Islands ◽  
Global Changes ◽  
The South ◽  
Positive Correlation ◽  
Paleoclimate Records

Abstract. Terrestrial paleoclimate records are rare in the South Atlantic, limiting opportunities to provide a prehistoric context for current global changes. The tussock grass, Poa flabellata, grows abundantly along the coasts of the Falkland Islands and other sub-Antarctic islands. It forms extensive peat records, providing a promising opportunity to reconstruct high-resolution regional climate records. The isotopic composition of leaf and root tissues deposited in these peats has the potential to record variation in precipitation, temperature, and relative humidity over time, but these relationships are unknown for P. flabellata. Here, we investigate the isotopic composition of P. flabellata plants and precipitation and explore seasonal relationships with temperature and humidity across 4 study locations in the Falkland Islands. We reveal that inter-seasonal differences in carbon and oxygen stable isotopes of leaf α-cellulose of living P. flabellata significantly correlated with monthly mean temperature and relative humidity. The carbon isotope composition of leaf α-cellulose (δ13Cleaf) records the balance of CO2 supply through stomata and the demand by photosynthesis. The positive correlation between δ13Cleaf and temperature and negative correlation between between δ13Cleaf and relative humidity suggest that photosynthetic demand for CO2 relative to stomatal supply is enhanced when conditions are warm and dry. Further, the positive correlation between δ13Cleaf and δ18Oleaf (r = 0.88, p 

scholarly journals Paleoclimate in continental northwestern Europe during the Eemian and early Weichselian (125–97 ka): insights from a Belgian speleothem

2016 ◽  
Vol 12 (7) ◽  
pp. 1445-1458 ◽  
Author(s):  
Stef Vansteenberge ◽  
Sophie Verheyden ◽  
Hai Cheng ◽  
R. Lawrence Edwards ◽  
Eddy Keppens ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Regional Climate ◽  
Time Interval ◽  
Last Interglacial ◽  
High Resolution Data ◽  
Climate Conditions ◽  
Spatial Coverage ◽  
Stable Conditions ◽  
Mis 5E ◽  
Δ13c And Δ18o

Abstract. The last interglacial serves as an excellent time interval for studying climate dynamics during past warm periods. Speleothems have been successfully used for reconstructing the paleoclimate of last interglacial continental Europe. However, all previously investigated speleothems are restricted to southern Europe or the Alps, leaving large parts of northwestern Europe undocumented. To better understand regional climate changes over the past, a larger spatial coverage of European last interglacial continental records is essential, and speleothems, because of their ability to obtain excellent chronologies, can provide a major contribution. Here, we present new, high-resolution data from a stalagmite (Han-9) obtained from the Han-sur-Lesse Cave in Belgium. Han-9 formed between 125.3 and  ∼  97 ka, with interruptions of growth occurring at 117.3–112.9 and 106.6–103.6 ka. The speleothem was investigated for its growth, morphology and stable isotope (δ13C and δ18O) composition. The speleothem started growing relatively late within the last interglacial, at 125.3 ka, as other European continental archives suggest that Eemian optimum conditions were already present during that time. It appears that the initiation of Han-9 growth is caused by an increase in moisture availability, linked to wetter conditions around 125.3 ka. The δ13C and δ18O proxies indicate a period of relatively stable conditions after 125.3 ka; however, at 120 ka the speleothem δ18O registered the first signs of regionally changing climate conditions, being a modification of ocean source δ18O linked to an increase in ice volume towards the Marine Isotope Stage (MIS) 5e–5d transition. At 117.5 ka, drastic vegetation changes are recorded by Han-9 δ13C immediately followed by a cessation of speleothem growth at 117.3 ka, suggesting a transition to significantly dryer conditions. The Han-9 record covering the early Weichselian displays larger amplitudes in both isotope proxies and changes in stalagmite morphology, evidencing increased variability compared to the Eemian. Stadials that appear to be analogous to those in Greenland are recognized in Han-9, and the chronology is consistent with other European (speleothem) records. Greenland Stadial 25 is reflected as a cold/dry period within Han-9 stable isotope proxies, and the second interruption in speleothem growth occurs simultaneously with Greenland Stadial 24.

The Great Falls Tectonic Zone: suture or intracontinental shear zone?

1998 ◽  
Vol 35 (2) ◽  
pp. 175-183 ◽  
Author(s):  
D E Boerner ◽  
J A Craven ◽  
R D Kurtz ◽  
G M Ross ◽  
F W Jones
Keyword(s):  
Shear Zone ◽  
Foreland Basin ◽  
Oceanic Lithosphere ◽  
Plate Edge ◽  
Tectonic Zone ◽  
Magmatic Arc ◽  
Tectonically Active ◽  
Proterozoic Basement ◽  
Wyoming Province ◽  
Remote Sensing Methods

The Great Falls Tectonic Zone is generally considered to be the boundary between the Archean Hearne and Wyoming provinces. Although completely buried beneath the western Canadian sedimentary basin, the zone can be studied indirectly through variations in Phanerozoic sedimentation patterns, faulting, basement geochronology, and xenoliths, and with geophysical remote sensing methods. While tectonically active ca. 1.8 Ga and clearly truncating the potential field fabrics of Wyoming Province and Medicine Hat Block, the Great Falls Tectonic Zone lacks a colinear magmatic arc, suggesting that the Hearne-Wyoming juxtaposition did not involve subduction of oceanic lithosphere. Furthermore, electromagnetic studies fail to detect a response that can be interpreted as a plate-edge foreland basin, typical of exposed Proterozoic suture zones. The only conductivity anomaly associated with the zone is weak and appears at depths exceeding 20 km, well below the top of the Proterozoic basement. Taken together, these observations suggest the Great Falls Tectonic Zone may be better interpreted as a reactivated Archean(?) intracontinental shear zone rather than a Proterozoic age suture between Archean provinces.

scholarly journals Timing of Contractional Tectonics in the Miocene Foreland Basin System of the Umbria Pre-Apennines (Italy): An Updated Overview

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 97
Author(s):  
Francesco Brozzetti ◽  
Daniele Cirillo ◽  
Lucina Luchetti
Keyword(s):  
Late Miocene ◽  
Structural Unit ◽  
Multidisciplinary Approach ◽  
Foreland Basin ◽  
Calcareous Nannofossil ◽  
Large Dataset ◽  
Calcareous Nannofossil Biostratigraphy ◽  
Early Late ◽  
Basin System ◽  
Over Time

A large dataset of lithostratigraphic and biostratigraphic data, concerning the Early-Late Miocene turbidite succession of the Umbria pre-Apennines, is presented and analyzed. The data come from the study of 24 sections that are representative of all the main tectonic units cropping out between the front of the Tuscan allochthon and the Umbria-Marche calcareous chain. The sections have been dated using quantitative calcareous nannofossil biostratigraphy and, wherever possible, they were correlated through key-beds recognition. Such a multidisciplinary approach allowed us to reconstruct the evolution of the Umbria foredeep over time and to unveil the chronology of compressive deformations by defining: (i) the onset of the foredeep stage in each structural unit, (ii) the age of depocenter-shifting from a unit to the adjacent one, (iii) the progressive deactivation of the western sector of the foredeep due to the emplacement of allochthon units, and (iv) the internal subdivisions of the basin due to the presence of foreland ramp faults or thrust-related structures. A further original outcome of our study is having brought to light the Late Burdigalian “out-of-sequence” reactivation of the Tuscan allochthon which bounded westward the foredeep, and the subsequent protracted period of tectonic stasis that preceded the deformations of the Umbrian parautochthon.

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