Middle Devonian lycopsids from high southern palaeolatitudes of Gondwana (Argentina)

Abstract

-Fossil plants are described from the upper part of the Devonian Lolén Formation, Sierra de la Ventana, Buenos Aires Province, Argentina, in the area of Estancia Las Acacias. The sequence is composed mainly of dark grey shales, and fossils were found in a single horizon where thin interlayered beds of fine reddish-brown micaceous sandstones appear where the environment of marine deposition became more shallow. The age of the Lolén Formation is presently established on the basis of brachiopods, these being characteristic elements of the Malvinokaffric realm from the Gondwana Lower Devonian (Emsian). The fossil plants are remarkably preserved given that they are in rocks that have undergone intense deformation. The plants are identified as Haplostigma sp. and Haskinsia cf. H. colophylla, and suggest a Middle Devonian age (Givetian) for the fossil-bearing levels. Haskinsia, identified on the basis of leaf morphology, is the first well-delimited Middle Devonian lycopsid genus described from Argentina, and the record from the most southerly palaeolatitude. During the Middle Devonian, Haskinsia was distributed in tropical, warm temperate and high southern latitude, ?cool temperate zones.

Lycopsids from the Upper Devonian of northern Chile with remarks on the geographical distribution of the morphogenus Haplostigma Seward

“…with spine-like appendages and no true leaves. This has been done for Devonian material from all over Gondwana (Plumstead 1967;McLoughlin and Long 1994;Gutiérrez 1996;Gutiérrez and Archangelsky 1997;Cingolani et al 2002;Di Pasquo et al 2009). …”

“…Berry et al 2000;Cingolani et al 2002;Edwards et al 2001a, b;Gerrienne et al 2001;Di Pasquo et al 2009). However, occurrences of Devonian plants in Chile have not yet been documented in detail.…”

Mid-Late Devonian assemblages of herbaceous lycophytes from northern Argentina and Bolivia: Age assessment with palynomorphs and invertebrates and paleobiogeographic importance

“…9). Based on the reconstruction of the paleoclimatic zones here, reproduced from Scotese in Cingolani et al (2002;see Fig. 10), these floras appear to have developed around 55 e75 S palaeolatitude in Southern Gondwana mostly during the Eifelian e Givetian (Argentina, Bolivia, Brazil, South Africa, Antarctica, Australia).…”

Tectonic Insight in the Southwest Gondwana Boundary Based on Anisotropy of Magnetic Susceptibility

“…The Lolén Formation, of Devonian age [27], is at the top of the Ventana Group. It has micaceous sandstones, phyllites and shales with lenticular beds of fine conglomerate, with a strong cleavage in northwest-southeast direction.…”