Abstract Detail

Paleobotany

Meyer-Berthaud, Brigitte [1], Decombeix, Anne-Laure [1], Girard, Catherine [2], Steemans, Philippe [3], Blanchard, Romain [1], Champreux, Antoine [1], Evreinoff, Mathilde [1].

The Famennian flora of Barraba, New South Wales, Australia.

Paleozoic floras of Gondwana, the largest paleocontinent of its time and cradle of terrestrial plants, are notoriously understudied. In Australia, a few studies have been published on plants of Late Devonian age, but they are old and need reinvestigation. This presentation is an account of the Famennian flora found in the marine beds of the Mandowa Mudstone Formation at Barraba. Four localities have been investigated along the banks of the Manilla river. All yielded adpressions but only one, the historical locality discovered by Mr. John Irving, provided anatomically preserved specimens. Despite extensive search, no marine fossils were found that could provide stratigraphic information on the plant beds. The sediments do not contain palynomorphs either, except at one place where they are rare. Here they correspond to the LN palynozone, just below the Devonian-Carboniferous boundary. Eleven anatomically preserved specimens are reported at Barraba, which are assigned to nine taxa. The lycopsids include a large cone assigned to the genus Cymastrobus, and a small fragment of axis recently recognized as a new genus, Lycaugea. Differences in their stelar architecture indicate that Cymastrobus and Lycaugea represent different plants, both interpreted as basal members of the Isoetales. The iridopteridalean axis Keraphyton is large and characterized by a highly divided actinostele. The Cladoxylopsida is the most diverse group, with axes referred to as Polyxylon australe, Cladoxylon cf. taeniatum, Cladoxylon radiatum and Hierogramma sp. The poorly preserved wood of a 10 cm wide log shows the groups of bordered pits characterizing the archeopteridalean genus Callixylon. Spermatophytes are represented by a single fragment of petiole assignable to Kalymma grandis. The most abundant remains preserved as adpressions are referrable to the cosmopolitan lycopsid genus Leptophloeum. Most other plant fossils are axes of uncertain affinities. Some, with regular ribs on the outer surface, may correspond to cladoxylopsids. Spermatophytes are represented by bifurcate fragments of fronds lacking pinnules, and a possible seed. Spore-producing plants are the dominant components of this allochtonous flora which may correspond to plants living in coastal habitats or along river banks. Except for the three genera specific to Barraba, the generic composition of this Australian flora resembles that of late Famennian to early Tournaisian localities of the New Albany Shale in eastern USA, the Russchiefer of Thuringia (Germany) and the Lydiennes of Montagne Noire (southern France), suggesting free dispersal between these zones, and comparable environmental conditions.

1 - AMAP, Univ. Montpellier, Cirad, Cnrs, Inrae, Ird, Montpellier, France
2 - ISEM, Univ. Montpellier, Cnrs, Montpellier, France
3 - Geology, Université de Liège, Liège, Belgium

Keywords:
Devonian
Flora
Gondwana.

Presentation Type: Oral Paper
Session: PL4, Paleobotany: Honoring Fran Hueber - Session II
Location: /
Date: Tuesday, July 20th, 2021
Time: 2:00 PM(EDT)
Number: PL4007
Abstract ID:108
Candidate for Awards:None