Astrochronology and radio-isotopic dating of the Alano di Piave section (NE Italy), candidate GSSP for the Priabonian Stage (late Eocene)

Abstract The Varignano section (Trento province, northern Italy) provides an exceptional opportunity for a direct correlation between shallow benthic (SB) zones and standard calcareous plankton zones at the Bartonian–Priabonian transition (middle–late Eocene). This transition has attracted great attention by biostratigraphers in the last decades in searching for a boundary stratotype section. The Alano di Piave section (NE Italy) is the leading candidate for the base Priabonian Global Stratotype Section and Point (GSSP). However, at Alano, larger foraminifera-bearing resedimented levels occur exclusively well below the critical interval. Conversely, the Varignano section, located ∼80 km west of the Alano section, preserves several coarse bioclastic levels rich in larger foraminifera throughout the section. These levels are intercalated with basinal marlstones, crystal tuff layers, and an organic-rich interval. The Varignano section spans planktic foraminiferal Zones E10 and E11 to lower E14, calcareous nannofossil Zones MNP16Bc to MNP18 and Chrons 18n to 17n.2n. The main calcareous plankton events recently proposed as primary base-Priabonian correlation tools, i.e., the last occurrence of the genus Morozovelloides and the Base common (= acme beginning) of Cribrocentrum erbae occur, respectively, within C17n.3n and C17n.2n. We correlate prominent crystal tuff layers exposed at Varignano with those outcropping at Alano, including the Tiziano bed, whose base has also been proposed as the GSSP level. The Varignano section spans the upper SB17 and the lower SB18 Zones, with the zonal boundary marked by the first occurrence of the genus Pellatispira. This event occurs in the lower part of Zones E13 and MNP17A within C18n, well below all the potential criteria to identify the GSSP that also includes Chron C17n.1n base. We point out that the usage of shallow-water biostratigraphers in placing the base of the Priabonian at the base of Zone SB19 is inconsistent with the proposed plankton events.

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AGE AND PETROGENESIS OF ACID VOLCANITES OF THE ALGANSKY MOUNTAINS OF THE KORYAK HIGHLANDS (NORTHEASTERN OF RUSSIA)

Tikhookeanskaya Geologiya ◽

10.30911/0207-4028-2021-40-2-3-20 ◽

2021 ◽

pp. 3-20

Author(s):

P.I. Fedorov ◽

◽

A.V. Moiseev ◽

S.A. Palandzhyan ◽

I.V. Gul’pa ◽

...

Keyword(s):

Rare Earth ◽

Rare Earth Elements ◽

Distribution Pattern ◽

Late Eocene ◽

Island Arc ◽

Northwestern Part ◽

Crustal Anatexis ◽

Isotopic Dating

The isotopic dating of U-Pb by the zircon method of volcanic acid zircons of the Konachan complex (Algansky mountains, northwestern part of the Koryak highlands) confirmed their Late Eocene age (34.6 ± 0.5-38.8 ± 0.4 Ma, Priabon). It has been shown that silicic rocks are represented by moderately potassium, peraluminous (ASI = 1.23–1.30), moderately and high magnesian differences, often with a high content of Cr and Ni. The contents of Sr, Y and Yb are adakite. High ratios of 143Nd/144Nd and low 87Sr/86Sr in the rocks of the complex, the distribution pattern of rare and rare-earth elements suggest that the source of salite melt, to some extent contaminated by sedimentary material, was metabasites. The formation of the Konachan complex is caused by magmatism during accretion of terranes of the Olyutor-East Kamchatka island-arc system [27]; compression processes led to the blocking of the upwelling front of the continental asthenosphere, initiating intense crustal anatexis and silicate magmatism.

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New report of fossil crabs (Decapoda, Brachyura) from the late Eocene of San Feliciano Hill (Orgiano, Monti Berici, Vicenza, NE Italy)

Boletín de la Sociedad Geológica Mexicana ◽

10.18268/bsgm2021v73n3a120221 ◽

2021 ◽

Vol 73 (3) ◽

pp. A120221

Author(s):

Antonio De Angeli ◽

Alessandro Garassino

Keyword(s):

Original Description ◽

Morphological Characters ◽

Late Eocene ◽

Incertae Sedis ◽

Ne Italy ◽

Orbital Margin ◽

The Rich

The rich decapod assemblage from the late Eocene of San Feliciano hill (Orgiano, Monti Berici, Vicenza, NE Italy) was partially recorded by De Angeli and Garassino (2002, 2014). Herein, two new crabs, Bericirinia bretoni n. gen., n. sp. (Epialtidae MacLeay, 1838) and Orgianocarcinus bericus n. gen., n. sp. (Dairidae Ng and Rodriguez, 1986) are reported from San Feliciano Hill, located in Monti Berici, Orgiano. Moreover, two well-preserved specimens assigned to Actaeites lobatus Müller and Collins, 1991 (Xanthoidea MacLeay, 1838, incertae sedis) allowed to add some morphological characters to the original description of the holotype, lacking the fronto-orbital margin.

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