Matthew Chapin 1
Part III: Interpretation
1) Deposition of the Copacabana Formation is controlled by changes in global tectonics and
climate from the formation of Pangaea. Gondwana was drifting from mid to lower
latitudes during the Carboniferous (Grader, 1). Additionally, glacial deposition ended
during this time, and carbonates began to be deposited in Bolivia. The Titicaca Group is
believed to have been associated with a back-arc strike slip setting (Grader, 2). Followed
by marine transgression and volcanism. The back-arc setting would have resulted in low;
however, long term accumulation rates of sediment (Grader, 4). Lithologies such as shale
indicate significant relative sea level rise and coincide with marine transgression (Grader,
11). The stacking patterns of facies indicate that the Copacabana Formation was largely
influenced by eustatic fluctuations produced by glacial growth and retreat (Grader, 11).
Also, volcanism provides numerous ash beds in the upper portion of the core. Various
Paleontologists have studied biota from the Copacabana Formation in Bolivia. Fusulinids,
conodonts, corals, and bryozoans have all been useful for correlation (Grader, 6).
Furthermore, conodonts and fusilinids are incorporated with radiogenic dates and used
for chronostratigraphy.
2) The core measured for this project comes from the upper member of the Copacabana
Formation in the lower Permian. P2 SB (Grader, 12) most likely matches the sequence
boundary found near the 823m mark on the core. The reasoning for this is that there are
two sequence boundaries within the upper member and P2 SB is the first sequence
boundary, which happens to match the boundary on the core. Also, The P2 SB found on
Matthew Chapin 2
figure 8 changes from HST to TST much like the sequence boundary drawn from the
core.
3) Some geologists imply that clamatorial restrictions separated southern Bolivia and
Argentina (Grader, 14). Others entail that mountain glaciers and glacigenic deposition
occurred coinciding with carbonate deposition (Grader, 14). Implications could simply be
that southern Pangaea was capped with polar ice; including southern Bolivia and
Argentina.