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Radiometric dating of the Tertiary volcanics in Lower Silesia, Poland. V. K-Ar and palaeomagnetic data from Late Oligocene to Early Miocene basaltic volcanics of the North-Sudetic Depression

100%

Birkenmajer K. , Pécskay Z. , Grabowski J. , Lorenc M. W. , Zagożdżon P. P.

Annales Societatis Geologorum Poloniae

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2007

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tom Vol. 77, No 1

1-16

EN

This is the fifth contribution to geochronological, petrologic-geochemical and palaeomagnetic studies of the Tertiary basaltoids of Lower Silesia, Poland. It covers the area of the North-Sudetic Depression close to its contact with the Fore-Sudetic Block (6 new sites). The oldest K-Ar date was obtained from basanite plug at Sichów (BP-34: 27.80ą1.27 Ma) located exactly on the Sudetic Marginal Fault. It determines the age of the fault as Late Oligocene. Five other sites (BP-35-39) yielded radiometric ages between 20.07ą0.90 Ma and 18.72ą0.81 Ma (Early Miocene). The volcanics investigated are typical within-plate basaltoids represented by ankaratrite and basanite. The Late Oligocene Sichów intrusion (BP-34) is normally magnetized, the Early Miocene basaltic rocks (ankaratrite BP-39 and basanites: BP-35-38) reveal reversed magnetization.

PL

Piąta część datowań K-Ar i badań paleomagnetycznych trzeciorzędowych wulkanitów Dolnego Śląska obejmuje odsłonięcia tych skał w obszarze niecki północnosudeckiej, w sąsiedztwie sudeckiego uskoku brzeżnego. Otrzymano sześć dat w granicach 27,80š1,27 Ma (późny oligocen: Sichów, BP-34) – 18,72š0,81 Ma (niższy miocen = burdygał: Wilków, BP-37). Późnooligoceńska data dla ankaratrytowego czopu Sichowa (BP-34), który znajduje się na sudeckim uskoku brzeżnym, określa taki wiek tego uskoku. Zbadane skały bazaltowe – bazanity i ankaratryty (melabazanity) są typowymi przedstawicielami wulkanizmu sródpłytowego. Skład chemiczny ogniska magmowego podlegał ewolucji, co przejawiło się w badanych skałach wzrostem zawartości potasu i kobaltu w okresie czasu między wyższym oligocenem a niższym miocenem. Czopy ankaratrytu i bazanitu zostały zbadane pod względem paleomagnetycznym: najstarszy z nich, 27,80 Ma (BP-34: ankaratryt) wykazuje namagnesowanie normalne, pozostałe pięć, 20,07–18,72 Ma (BP-39: ankaratryt; BP-35–38 – bazanity) wykazuje namagnesowanie odwrócone.

2

Radiometric dating of the Tertiary volcanics in Lower Silesia, Poland

100%

Birkenmajer K. , Pécskay Z. , Grabowski J. , Lorenc M. W. , Zagożdżon P. P.

Annales Societatis Geologorum Poloniae

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2004

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tom Vol. 74, No 1

1-19

EN

The Tertiary volcanic rocks of the Fore-Sudetic Block (FSB), Lower Silesia (Poland), exposed between Strzelin in the east and Legnica in the west, typically represent within-plate basalts. Petrologically, they consist mainly of alkali basalts, basanites, tephrites and ankaratrites. 16 new K-Ar dates are recorded, spanning the Oligocene (31 Ma) through Early Miocene (Burdigalian c. 18 Ma) time. The majority of these K-Ar dates plot around two significantly different ages: 27š1.5 Ma, and 20š1.5 Ma. They indicate the presence in the FSB of two distinct separate phases of Tertiary vulcanicity: (i) the first phase, mainly Late Oligocene (Chattian), with a peak at c. 27; (ii) the second phase, Early Miocene (Aquitanian-Burdigalian), with a peak at about 20 Ma. These phases seem to be separated by a gap in vulcanicity about 3 Ma long at the Oligocene/Miocene boundary. Correlation of K-Ar-dated volcanic activity in the FSB with specific radiometrically-dated polarity intervals, poses some problems, and cannot be regarded definite at this stage of investigations. Considering the whole set of K-Ar and palaeomagnetic data from 40 sites, between the Opole area in the east and the Legnica area in the west, we suggest that volcanism of the first phase (Oligocene), although significantly spread out in time across multiple reversals, took place mostly during two well-defined, previously recognized events: (i) an older, reversed Odra event (within the C9r chron: 28.1š1.2 Ma); and (ii) a younger, normal Gracze event (within the C8n chron: 26.5š1.1 Ma). The second phase (Early Miocene) volcanism includes mainly a continuous set of reversely magnetized sites (mostly a single reversed C6r chron: 20.5š0.87 Ma).

3

Isotope age constraint for the Blue Dyke and Jardine Peak subvertical instrusions of King George Island, West Antarctica

100%

Panczyk M. , Nawrocki J. , Williams I. S.

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tom 30

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nr 4

379-391

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A termite from the Late Oligocene of northern Ethiopia

84%

Engel M. S. , Pan A. D. , Jacobs B. F.

Acta Palaeontologica Polonica

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2013

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tom 58

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nr 2

EN

Termites of the family Stolotermitidae are a relict lineage of primitive Isoptera. The fossil record of Stolotermitidae is exceptionally poor, with only two Miocene (Neogene) species documented to date. Herein, a new genus and species of Paleogene termites is described and figured from the Late Oligocene (28–27 Ma, Early Chattian) of northwestern Ethiopia (Amhara Region, Chilga Woreda). Chilgatermes diamatensis gen. et sp. nov., is most similar to genera of the Stolotermitidae, Archotermopsidae, and Termopsidae but can be distinguished on the basis of forewing venational details. The genus is tentatively placed in the Stolotermitidae: Porotermitinae. Chilgatermes diamatensis is the first fossil termite from Ethiopia and, indeed, the first from the entire African continent.

5

Late Oligocene sharks and rays from the Chandler Bridge Formation, Dorchester County, South Carolina, USA

84%

Cicimurri D. J. , Knight J. L.

Acta Palaeontologica Polonica

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2009

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tom 54

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nr 4

EN

A diverse vertebrate fauna, dominated by elasmobranch taxa, was collected from the upper Oligocene (Chattian) Chandler Bridge Formation in Summerville, Dorchester County, South Carolina. Nearly 3,500 teeth and dermal denticles are assigned to 29 species of sharks and rays, and our sample includes the oldest known occurrence of the whale shark, Rhincodon, as well as a new skate, Raja mccollumi sp. nov. The Chandler Bridge elasmobranch assemblage is comparable in species diversity to Chattian assemblages of Virginia and North Carolina, USA, and Germany. Notable absences from Germany include Rhincodon, Hemipristis, and Sphyrna zygaena, likely reflecting the influence of colder water on the North Sea Basin during the Chattian. Squaloids, pristiophoroids, and hexanchoids are known from Chattian deposits of the Albemarle Embayment (North Carolina), Salisbury Embayment (Virginia), and North Sea Basin, but these taxa are absent from the Chandler Bridge assemblage, perhaps because of shallow, warm water (20 to 25°C) conditions within the more southerly Charleston Embayment.

6

A nearly complete skeleton of the fossil galliform bird Palaeortyx from the late Oligocene of Germany

67%

Mayr G. , Poschmann M. , Wuttke M.

Acta Ornithologica

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2006

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tom 41

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nr 2

7

New artiodactyl ruminant mammal from the Late Oligocene of Pakistan

67%

Metais G. , Antoine P. O. , Marivaux L. , Welcomme J. L. , Ducrocq S.

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2003

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tom 48

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nr 3

EN

Dental and postcranial material of the bovid−like ruminant Palaeohypsodontus zinensis sp. nov. is reported from the Oligocene of the Bugti Hills (Balochistan, Pakistan). This finding extends the geographic distribution of this dentally highly derived ruminant, which was previously restricted to the early Oligocene of Mongolia and China. The inclusion of Palaeohypsodontus within the Bovidae is disputed on the basis of astragalus characters, and the taxonomic status of the Oligo−Miocene Eurasian bovid−like ruminants is briefly discussed. It is concluded that the assignment of Palaeohypsodontus to the Bovidae would be premature. More dental and postcranial material of this genus as well as additional fossils of early bovids are necessary to shed new light on the phylogenetic relationships within the first representatives of that family in Eurasia.

8

A contribution to the Neogene history of Fagaceae in the Central Balkan area

67%

Palamarev E. , Ivanov D.

Acta Palaeobotanica

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2003

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tom 43

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nr 1

9

Remarks on palaeoenvironmental changes based on reviewed Tertiary insect associations from the Krusne hory piedmont basin and the Ceske stredohori Mts in Northwestern Bohemia [Czech Republic]

67%

Prokop J.

Acta Zoologica Cracoviensia

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2003

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tom 46

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nr Suppl.

EN

Cenozoic insect fauna of northwestern Bohemia is preserved in fluviolacustrine deposits of the Krušné hory piedmont basins and the České středohoří Mts. The fossil insect assemblages are correlated with palaeobotanical results. The local palaeoenvironmental conditions such as the distance from the shoreline or water depth are interpreted. A reflection of changes in distribution of fossil entomofaunas is compared with relevant world localities of different palaeoenvironments. The sparse fossil insect taphocoenoses fill a gap in record of significant diverse non-marine invertebrate communities and serve for reconstruction of terrestrial palaeoecosystems. The selected fossil sites demonstrate insect taphocoenoses formed under conditions of the palaeoenvironment of a diatomaceous lake with subtropical forests (Kučlín), lowlands of riparian and mesophytic forests (Kundratice - Seifhennersdorf), warm-temperate swamp to riparian forests (Bílina mine) and lake sedimentation near mixed mesophytic forests (Mokřina). The aim is to compare fossil entomofaunas from several periods within Tertiary in northwestern Bohemia and search for analogous palaeoenvironmental conditions in other areas. The results are correlated with the previously proposed palaeobotanical models.