Palynology and organic geochemistry of an early to Middle Devonian succession from TCB X-1001– tacobo borehole, sub-Andean basin, southern Bolivia

A new chitinozoan assemblage from the Middle Devonian Los Monos Formation (sub-Andean basin, southern Bolivia) and its biozonal implications for Western Gondwana

“…The TCB X-1001-Tacobo borehole was drilled in the eastern sector of the sub-Andean ranges (the ‘Foothills’), in southern Bolivia ( Fig 1 ). Previous palynological work on this well was published in detail by García Muro et al [ 3 ] in which the marine deposits of the Icla, Huamampampa and Los Monos formations were analysed and the corresponding geology and stratigraphy were extensively described.…”

“…This high palaeolatitude and shallow marine deposits suggested cold sea conditions and a palaeobathymetry of no more than 200 m [ 11 , 12 ]. Although the middle and upper Palaeozoic tectonic setting along the Bolivian basins is still under debate (see [ 3 ]), the sedimentary infill is considered to be made up of several overlapping sedimentary basins.…”

“…Previous studies dated the Los Monos Formation as late Eifelian [ 17 , 20 ], late Eifelian-late early Givetian to late Givetian [ 21 ] and early-middle Givetian to Frasnian [ 7 ]. García Muro et al [ 3 ] have constrained the age of the Los Monos Formation, in the Tacobo borehole, to the late Eifelian?–middle Givetian, based on miospore and organic-walled phytoplankton assemblages.…”

“…Most of the previous biostratigraphical studies in these basins are based on palynological data due to the scarcity of other useful fossil groups [ 2 ]. The complete list of previous palynological studies in the area can be found in García Muro et al [ 3 ].…”

“…The samples studied come from the Icla, Huamampampa and the Los Monos formations. The phytoplankton and miospores were described by García Muro et al [ 3 ], thus the present study focuses on the chitinozoans from the Los Monos Formation, which is the other important palynological marine group.…”