A low-diversity brachiopod assemblage from the upper member of the Zorritas
Formation in the Sierra de Almeida, northern Chile, further confirms the p
resence of Lower Carboniferous (Tournaisian) strata in that region. Key tax
a include Schuchertella? sp., Chilenochonetes anna new genus and species, P
aurorhyncha chavelensis (Amos), and Septosyringothyris covacevichi new spec
ies. Other elements of the assemblage, including Paraconularia sp., Posidon
iella sp., Bellerophon (Bellerophon) sp.. Eocanites sernageominus, and Imit
oceras? sp. support this Early Carboniferous age assignment. Local distribu
tion of taxa suggests small-scale environmental control. Rhynchonelloid and
syringothyroid shells, many articulated, occur in lenticular sandstone bod
ies that were deposited in deltaic distributary channels; chonetids, schuch
ertellids and mollusc-bearing, iron-rich concretions are found in siltstone
s and mudstones that reflect interdistributary quiet-water settings and pos
sibly a delta-front setting. Certain elements of this fauna are also presen
t in northwestern Argentina and Peru, indicating a regional nearshore elast
ic regime, The closest correlation elsewhere is with the Tournaisian faunas
of southeastern Australia, although analogous big-shell assemblages are fo
und in lower Mississippian elastic strata of the central Appalachians, Ohio
, and Indiana.