The Effects of
Magmatism on the Reservoir Potential of Sandy Deep Marine Successions of Southern
California and the Borderland Region
Marsaglia, Kathleen M.1, David
A. Clague2, Alice S. Davis2 (1) California State
University Northridge, Northridge, CA (2) Monterey Bay Aquarium Research
Institute (MBARI), Moss Landing, CA
The dominantly quartzofeldspathic
(arkosic) compositions of Upper Cretaceous to Paleogene sandstones in southern California are products of
batholith unroofing and dissection. Locally, these sandstones exhibit
significant compaction and cementation by carbonate, and lesser clay-mineral,
quartz and feldspar cements. Oligocene-Miocene triple-junction formation and
plate reorganization resulted in local changes in sand composition associated with
magmatism, recycling of uplifted sedimentary units, and crustal extension.
These trends are apparent from onshore (mainland and island) outcrop and
subsurface studies as well as from offshore Deep Sea Drilling Project sites and
dredges located in the outer California borderland region. Our
recent deep marine exploration of the outer California borderland using MBARI's
(Monterrey Bay Aquarium Research Institute) R/V Western Flyer and the ROV
(remotely operated vehicle) Tiburon suggests a complex felsic to mafic magmatic
history for the area that includes a distinct period (~16 Ma) of calcalkaline
volcanism on the Patton Ridge. Because volcanic components (e.g., vitric ash
and crystals) add diagenetic complexity to potential reservoir sandstones,
understanding the distribution and chemistry of offshore magmatism is important
in predicting the reservoir characteristics of post-Oligocene deep-marine sandy
facies within the region.