Dasycladalean algae distribution in ammonoid-bearing Middle Triassic platforms (Dolomites, Italy)

Abstract

This paper gives an account of distribution of Dasycladales in ammonoid-bearing Middle Triassic carbonate platforms of the Dolomites. A ca. 600-m-thick section was investigated within the Latemar platform interior and Dasycladales from correlated ammonoidbearing samples of the Marmolada platform were studied for comparison. At Latemar, the dense sampling allowed, with some confidence, the identification of the first occurrences of Diplopora nodosa and Gyroporella ladinica, and the last occurrences of D. annulatissima and D. comelicana. Their stratigraphic range was found to be in agreement with literature. Other first or last occurrences could not be reconciled with known distributions, and were considered as environmentally or palaeogeographically controlled. All four algal events occur within a narrow interval of two Illyrian (Upper Anisian) ammonoid subzones (avisianum and crassus subzones). This study demonstrates the biostratigraphic potential of Dasycladales in platform settings, and highlights the necessity of detailed stratigraphic studies to determine their distribution

Facies, depositional environment, and palaeoecology of the Middle Triassic Cassina beds (Meride Limestone, Monte San Giorgio, Switzerland)

“…Endotriadella is regarded as living infaunally in shallow-marine conditions (Jones and Charnock 1985). As dasycladaleans thrive in shallow-marine waters down to 10-12 m depth but show mass occurrences only down to 6 m depth (Piros and Preto 2008), the presence of these algae indicates a source area located at very shallow depths.…”

The Latemar: A Middle Triassic polygonal fault-block platform controlled by synsedimentary tectonics

“…Ammonoid distribution from Manfrin et al, 2005. Dasycladalean algae distribution from Piros and Preto, 2008. Margins can be nearly rectilinear for considerable distances, as on the NNE side between Cimon and Forcella Toac (46°22′43.693″N 11°36′31.412″E). The margin is rectilinear also at Cima Feudo (46°21′ 29.195″N 11°34′11.707″E) and Piz dei Muss (46°21′36.476″N 11°34′ 46.265″E), although here the platform is dissected by NNW-SSE faults with an Alpine strike-slip component.…”

“…Ammonoids are common in the platform (Assereto and Kendall, 1977;Brack and Rieber, 1993;De Zanche et al, 1995;Gaetani et al, 1981;Manfrin et al, 2005) and, along with dasycladacean algae (Piros and Preto, 2008), allow a detailed biostratigraphy of the platform. More specifically, the occurrence of numerous ammonoid-bearing horizons provides the biostratigraphic ages of the lithozones .…”

The Allocyclic Interpretation of the ‘Latemar Cycles’ (Middle Triassic, the Dolomites, Italy) and Implications for High‐Frequency Cyclostratigraphic Forcing

“…comm. 2006;Piros and Preto, 2008). In terms of correlation to the Latemar, D. annullatissima occurs only in the lowermost part of the Latemar succession (Gaetani et al, 1981) and P. paucifoliata is even older.…”