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Strontium isotope dating of bivalve faunas from the Upper Miocene Cacela Formation, eastern Algarve, Portugal: evidence from Messinian bivalve fauna

100%

Studencka B. , Zieliński G.

Geological Quarterly

2013

tom Vol. 57, No. 4

665–-686

The study is focused on the determination of the geological age of bivalve fauna recovered from four fossiliferous sequences in the Cacela Formation of Algarve, southern Portugal, by means of the strontium isotope stratigraphy. Forty two analyses of bivalve samples from Barroquinha, Cabanas, the Cacela River and Lacem were performed. The estimated age based on the 87Sr/86Sr ratios in bivalve shell samples from the Cacela River (a reference section for the Cacela Formation) is 7.6 ± 0.4 Ma and is consistent with a late Tortonian age suggested by micropalaeontological data (calcareous nannofossils and planktonic foraminifers). Moreover, strontium isotopic data record that the oldest age of the bivalves of the Cacela Formation (Lacem site) is at least 8.9 ± 0.4 Ma whilst the age of about 7.0 ± 0.5 Ma can be inferred for bivalves from Barroquinha. An intriguing new datum comes, however, from the bivalve strontium isotopic data of the Cabanas section which records the estimated age of about 6.7 ± 0.4 Ma and, therefore, an early Messinian age. This is the first report of the early Messinian marine bivalve fauna in Portugal. Sixty one bivalve species have been recovered in the Messinian of Cabanas. Four of them: Pseudopythina macandrewi (P. Fischer), Coripia corbis (Philippi), Glossus (Glossus) humanus (Linnaeus) and Cyathodonta dollfusi (Cossmann et Peyrot) have previously not been reported from the Miocene of southern Portugal.

A silicoflagellate plexus associated with Bachmannocena diodon subsp. nodosa from the Eastern Equatorial Pacific (Ocean Drilling Program Leg 138)

72%

Szaruga A. , Mccartney K. , Witkowski J.

Acta Geologica Polonica

2022

tom Vol. 72, no. 2

145--158

Upper Miocene (~6 Ma) sediments from a north-south transect of Ocean Drilling Program Holes 848B, 849B, 850B, 851B across the equator in the Eastern Pacific Ocean record an episode of unusual skeletal variability associated with the silicoflagellate Bachmannocena diodon subsp. nodosa (Bukry) Bukry, 1987. Skeletons in this plexus persisted for between 55,000 and 75,000 years and include an arch across a 2-sided basal ring, a highly unusual morphology for the genus. Groups of skeletal morphotypes were common within the plexus episode, and occur in a systematic sequence that is consistent between sites. As a result of this study, silicoflagellates previously placed in the genus Neonaviculopsis Locker and Martini, 1986 are now considered part of the Bachmannocena diodon subsp. nodosa plexus.

Dragonflies preserved in transparent gypsum crystals from the Messinian [Upper Miocene] of Alba, Northern Italy

72%

Schluter T. , Kohring R. , Gregor H. J.

Acta Zoologica Cracoviensia

2003

tom 46

nr Suppl.

From the Upper Miocene (Messinian) of the Alba area in Piedmont, northern Italy, are fossil dragonflies (mainly larvae) described, which were preserved in transparent gypsum crystals. The specimens belong probably to a single species (Oryctodiplax gypsorum), but occur in various pre-imaginal stages. This individual-rich but species-poor palaeoentomofauna appears to be almost autochthonous in origin and may have developed under hypersalinar conditions in a lagoonal environment during the Messinian salinar event.

Description of a new stromateoid fish from the Miocene of St. Eugene, Algeria

58%

Carnevale G. , Bannikov A. F.

Acta Palaeontologica Polonica

2006

tom 51

nr 3

A single specimen of the axial skeleton of an elongate fossil stromateoid fish, collected from the Upper Miocene (Messinian) St. Eugène locality of north−western Algeria, is identified as a new species Ariomma geslini sp. nov. of the family Ariommatidae. It is based on a unique combination of features, including morphology and arrangement of pleural ribs, structure and orientation of anterior portion of the anal fin, unique sequential arrangement of anal−fin pterygiophores in relation to the haemal spines, and presence of large cycloid scales and meristics. The morphology and orientation of the first anal−fin pterygiophore indicate that A. geslini sp. nov. is probably related to the amphi−Atlantic species A. bondi and A. melanum. The analysis of the fossil record of the Stromateoidei suggests that the ariommatids were already in existence at least as early as the Eocene.