title: Santa Juana Formation
text: # Santa Juana Formation
  
  Santa Juana Formation a Late Triassic (Carnian stage) sedimentary rock formation near Santa Juana in the lower course of the Biobío River in south-central Chile. Lithologies range from conglomerate sandstone, arkosic sandstone, siltstone and mudstone.
  
  ## Description
  
  The sediments that consolidate into the rocks of the formation deposited in alluvial, fluvial, lacustrine and playa lake environment. Overall, the formation is rich in plant fossils.
  
  The formation was deposited over the rocks of the Coastal Batholith of central Chile in a sedimentary basin that formed along the Gastre Fault. It has been posited that the basin developed as a rift during the early break-up of Gondwana in the Triassic.
  
  ## Fossil content
  
  The following fossils have been reported from the formation:
  
  ### Flora
  
  * Asterotheca fuchsii
  * A. rigbyana
  * Baiera africana
  * B. furcata
  * Cladophlebis mendozaensis
  * Dicroidium coriaceum
  * D. crassinervis
  * D. elongatum
  * D. odontopteroides
  * Dictyophyllum fuenzalidai
  * D. tenuifolium
  * Gleichenites quilacoyensis
  * Gontriglossa reinerae
  * Heidiphyllum elongatum
  * Kurtziana cacheutensis
  * Linguifolium lilleanum
  * L. steinmannii
  * Pterophyllum santajuanensis
  * Rissikia media
  * Saportaea dichotoma
  * Sphenobaiera africana
  * Sphenopteris cf. polymorpha
  * Taeniopteris sp.
  * Taeniopteris vittata
  * Telemachus elongatus
  * Thaumatopteris rothii
  * Todites chilensis
  * cf. Pseudoctenis fissa
  * Cladophlebis sp.
  * Dicroidium sp.
  * Gleichenites sp.
  * ?Antevsia sp.
  
  ### Insects
  
  * Bandelnielsenia chilena
  * Ischichucasyne santajuanaensis
  * Ademosyne sp.
  
  ### Branchiopoda
  
  * Polygrapta troncosoi
  * Menucoestheria terneraensis
  