The Santa Lucía Formation is located in southern Bolivia and is about in thickness. The formation is divided into three sections with the lower being made up of red-brown
mudstones with white to pink beds of
tuff being found throughout; these beds are largely found in the most basal parts of the section. Orange-brown bioturbated
siltstones can also be found at the basin margin within the Tiupampan strata. The middle section also is made up of mudstone though intercalated with turbidites and slumped blocks. Around the edges of the basin, red-brown mudstones along with conglomerate
sandstones can be found with these sandstones being where most vertebrate specimens are found. In one area, in the area of
Potosí, the lower part of the section is made up of sandy siltstones and mudstones though is largely made up of intercalations of
gypsum beds. Between the lower and middle sections of the formation, the trend of an increase coarseness can be seen along with a thickening-upwards succession. The upper section of the Santa Lucía Formation, similar to the lower section, is made up of red-brown mudstones though the layers found in the upper section also can contain green bands. The top section of the formation unconformity underlies the overlying Cayara Formation due to erosion. In contrast to this, the formation slightly unconformity overlies the El Molino Formation with it being described as transitional.
Dating The formation, as a whole, is poorly dated with ages generally ranging from the latest
Cretaceous and earliest
Cenozoic. However, the dating of the mammalian beds, like the Tiupampa locality, are much more well known. Originally, the mammal-bearing beds of the formation were dated to the late Cretaceous with later authors suggesting an early Paleocene date with the dating getting more specific since then. Marshall et al. had suggested that the beds dated to the late Paleocene, specifically Chron 26r. This suggestion was later refuted by Muizon in 1998 and more recent papers suggest a earliest Paleocene. In 2008, Gelfo et al. compared the fauna to those in both North and South America with the Tiupampan stage being most comparable to the
Puercan. In this paper, the authors also suggest that the fauna could be correlated with Chron 28r and, in turn, Pu3 which could suggest that the age of the fauna could range between 64-64.5 mya. Since this publication, the dating of Chron 28r has slightly changed at between 65 and 64.9 mya with more recent papers giving the fauna an age of 65 mya. == Paleobiota ==