Sprecher
Beschreibung
A well-preserved biota consisting of plant macrofossils, palynomorphs, insects, molluscs, crustaceans, actinopterygians and hybodontiforms has recently been recovered from the El Mono Formation in the Atacama Desert. Paleontological and sedimentological data indicate that this assemblage was deposited in a dominatingly lacustrine setting. The quality of preservation justifies classifying this site as a Fossil-Lagerstätte. Systematic sampling carried out since 2023 has yielded a rich flora dominated by the seed fern Dicroidium and its associated reproductive structures Umkomasia and Fanerotheca, alongside the sphenophytes Equisetites and Neocalamites. Less represented elements include cycadaleans, bennettitaleans, putative lycophytes and conifers, although this relative composition likely reflects a taphonomic and transport bias. This assemblage is consistent with a typical Late Triassic Gondwanan Dicroidium flora, reflecting a period of floral adaptation toward increasingly humid environments. Palynomorphs expand the floristic diversity, revealing the additional presence of bryophytes, dipteridaceans/matoniacean ferns, caytonialean seed ferns and a higher diversity of conifers, belonging to the voltzialean and coniferalean linages. Furthermore, the recurrent presence of charcoal points to paleowildfires, likely associated with warmer conditions punctuating an otherwise humid climate. Preliminary U-Pb detrital zircon geochronology data constrain the depositional age to the Middle to Late Norian (Maximum Depositional Age of ~211–214 Ma), coincident with the global record of enhanced warm and humid conditions during this interval. The El Mono flora thus provides a snapshot of the intensifying climatic conditions of a highly dynamic environment at the dawn of the modern ecosystems in Southwestern Gondwana.