High-Resolution Correlation of a Time-Bounded Unit of the Pisco Formation, Peru

<p>Correlation of beds in the Pisco Basin across significant distances is problematic and has not yet been effectively achieved. I chose to examine an interval bounded by two time markers, an 40Ar/39Ar-dated white tuff at the base and an 40Ar/39Ar-dated tuff couplet at the top. This interval was chosen because of the continuity and excellent exposure of the tuff beds at six distinct locations in a linear transect 30 km long. Correlation of units was achieved through 40Ar/39Ar dating, lithology, sedimentary structures, and magnetic susceptibility. The vertical and lateral variability in lithology, fossil assemblages, structures, and sequences was examined in detail and used to develop a paleoenvironmental model of the time-bounded sequence. Six distinct facies from the Pisco Formation were defined and used toward developing the paleoenvironmental model. Sedimentary structures associated with the facies, such as hummocky cross-stratification and ripple laminations, suggest wave reworking in a nearshore environment. The presence of clastics and coarse-grained sediments decrease from the northern outcrops to the southern outcrops, suggesting a decrease in energy levels and an increase of water depth away from the shore. This study provides the first secure correlation across a significant distance and a more comprehensive stratigraphy and paleoenvironmental interpretation of the Upper Pisco Formation.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Earth and Biological Sciences

Year

2015

Author dc:creator

• O'Hare, Daniel J.

Contributors dc:contributor

• Nick, Kevin E.
• Brand, Leonard R.
• Buchheim, H. Paul
• Nalin, Ronald

• Earth Sciences
• Geology
• Sedimentology
• Sediments (Geology) - Peru - Pisco Formation; Sedimentation and deposition - Peru - Pisco Formation; Geology; Stratigraphic - Miocene; Geology; Stratigraphic - Pliocene; Stratigraphic correlation; Sequence stratigraphy; Magnetic susceptibility; Radioactive dating
• Lithology; Sedimentary structures; Paleoenvironmental model; Cross-stratification; Ripple laminations

Statement dc:rights

• This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Language dc:language

English

Repository record dc:identifier

https://scholarsrepository.llu.edu/etd/333

OAI identifier oai:identifier

oai:scholarsrepository.llu.edu:etd-1335