The Miocene stratigraphy of the Laberinto area (Río Ica Valley) and its bearing on the geological history of the East Pisco Basin (south-central Peru)

Age and provenance of the Mio-Pleistocene sediments from the Sacaco area, Peruvian continental margin

“…1), five lithostratigraphic units (undifferentiated Pisco, Laberinto, Pampa, and Naranja members of the Pisco Formation, and Mature Formation; Fig. 2), which are correlative with the P0 and P1 allomembers, have been described (DeVries and Jud, 2018;DeVries et al, 2021). Similar sequence-stratigraphic architectures have not been identified in the southern EPB.…”

“…Sacaco sub-basin age constraints after Muizon and DeVries (1985); Ehret et al (2012);. Note that ages of the Chilcatay Fm are under debate (see DeVries et al, 2021).…”

“…An age-revision of the sub-basin rocks was undertaken by Ehret et al (2012) by integrating morphological traits of Carcharodon teeth, U-Pb geochronology, and strontium-based chemostratigraphy based on the LOWESS V.4 Fit table (McArthur et al, 2001). Additional radiometric dates for the Pisco Formation have been reported in different publications (see Ehret et al, 2012;DeVries et al, 2021), but have not yet been formally described yet. By contrast, the ages of the Caracoles and Pongo Formations had only been assessed through molluscan biostratigraphic data and considering the elevation of the Pleistocene terraces (DeVries, 2020).…”

“…The P0 is the lowermost allosequence and was deposited during the Langhian-Serravallian (Fig. 2 ;14.8-12.4 Ma;Bosio et al, 2020;DeVries et al, 2021). To date, in the Sacaco sub-basin there are no chronostratigraphically correlatable sequences to those of P0, as the oldest known Pisco deposits in the sub-basin are of Tortonian age (9.6-9.0 Ma; Fig.…”

“…However, new radiometric dates and stratigraphic correlations from the Laberinto area (Sula Section in the eastern flank of the Ica River Valley, see Fig. 1A) suggest that the P1 allomember would also include rocks as old as 12.5 Ma (DeVries and Jud, 2018;DeVries et al, 2021). Furthermore, a new formation (provisionally named Mature Formation, ~10-9 Ma) correlative with the P1 allomember was defined by DeVries et al ( 2021) for sedimentary rocks occurring on the eastern flank of the lower Ica River Valley (Mature Pampa) in the northern EPB (see Fig.…”