A new Middle–Late Jurassic flora and hot spring chert deposit from the Deseado Massif, Santa Cruz province, Argentina

Abstract

-We present an initial report of a well-preserved and relatively diverse Gondwanan plant assemblage from Bahía Laura Group, Chon Aike Formation strata of the Estancia Flecha Negra area, central-western region of the Deseado Massif, Santa Cruz province, Patagonia, Argentina. The locality contains the first richly fossiliferous chert with a diverse and well-preserved plant assemblage reported from the Mesozoic which is demonstrably associated with hot spring activity. A compression flora and petrified forest contained in associated clastic and volcaniclastic environments provide an indication of regional plant diversity during this as yet poorly represented stratigraphic interval.

Equisetum thermale sp. nov. (Equisetales) from the Jurassic San Agustín hot spring deposit, Patagonia: Anatomy, paleoecology, and inferred paleoecophysiology

“…The San Agustín hot spring complex occurs in the northwest area of the Deseado Massif, Santa Cruz province, Argentine Patagonia (Guido et al, 2010). Here, Late Jurassic volcanism, extension, and a high thermal gradient produced hydrothermal mineralization including epithermal deposits (e.g., Schalamuk et al, 1997) and their surface expression, hot spring deposits (e.g., Channing et al, 2007; Guido and Campbell, 2009; Guido et al, 2010). Hot spring sinters and cherts at San Agustín (Figs.…”

“…The phylogeny and evolutionary history of the genus Equisetum L. has attracted considerable recent attention from both neobotanists and paleobotanists. Molecular phylogenetic studies of the extant members of the genus have placed it as a sister group to the ferns and have resolved interspecific relations (e.g., Pryer et al, 2001, 2004; Des Marais et al, 2003; Guillon, 2004, 2007), but some systematic analyses of euphyllophytes resolve equisetophytes as sister to lignophytes (Rothwell, 1999). Molecular dating of the resulting phylogenies has suggested that the probable divergence of the extant crown group of the genus was 64.8 ± 12.7 million years ago in the Paleogene (Des Marais et al, 2003).…”

First Report of Fungi and Fungus-Like Organisms From Mesozoic Hot Springs

“…Microthyriales would have been well suited to the moist conditions of the Deseado Massif hot spring areas and probably were associated with conifers at the periphery of the geothermally influenced landscape. Dryland conifer forest fringes were commonly flooded by encroachment of geothermal wetland and sinter-apron environments (Channing et al, 2007;Guido et al, 2010). Such areas in active hot spring settings are characterized by drowned and decaying tree trunks and branches (Channing and Edwards, 2009b) The Jurassic San Agustín mycoflora holds an interesting diversity of chytrid and chytrid-like fossils.…”

Permineralized conifer-like leaves from the Jurassic of Patagonia (Argentina) and its paleoenvironmental implications

“…the occurrence of Mesozoic permineralized leaves in Patagonia is very rare. these include the unusual hot spring chert deposits from the La Matilde Formation and the Middle-Late Jurassic Chon Aike Formation, where permineralized scale leaves with preserved foliar tissues, belonging to araucarian-type and cycadophyte leaves, have been recorded, although they have not been fully described (Channing et al 2007, García Massini et al 2016.…”