 Current Projects 
As Collection Manager of the
microfossil collection at UCMP, my primary task is to organize and
database a century's accumulation of slides, samples, documents, and
literature so that this wealth of information can be readily accessed
for research and teaching at the museum and via the internet. There are
hundreds of thousands of slides containing millions (billions?) of
specimens awaiting my attention. Hopefully, my eyesight and sanity will
last long enough to fulfill a significant part of this mission before
my own fossilization ensues! You can visit the now rapidly expanding
microfossil database and learn more about these and considerably larger
fossils at the UCMP website.
As Museum Scientist, my research
interests are in the field of micropaleontology, particularly
Foraminifera and Ostracoda. I am currently involved in projects on the
Galapagos Islands and on Aegina Island (Greece), but primarily focused
on the microfossils of Chile and the Galapagos, and a modern microfauna in California, as
summarized below:
CHILEAN NEOGENE
In collaboration with ostracodologist
Dawn Peterson (UCMP Research Associate), malacologist Sven Nielsen
(GeoForschungsZentrum Potsdam), and sedimentologist Alfonso Encinas
(Universidad de Chile, Concepción), I have been studying microfossils
from numerous localities in south-central Chile, including the coastal
outcrops near Navidad that were first described by Charles Darwin in
1846. The purpose of my study is to resolve contradictory
interpretations of the age and depositional environments of the marine
units exposed along the central coast of Chile, which include the
Navidad Formation, the Ranquil Formation along Peninsula Arauco, and
the Lacui Formation of Chiloé Island. This study is particularly
challenging because the only good exposures of these rocks are the
extensive coastal bluffs and beach terraces, which consist of
low-dipping beds that apparently span just one or two short intervals
of geologic time. (In contrast, California's coasts, canyons, and
roadcuts typically reveal highly tilted strata where considerably
longer intervals of geologic time can be readily traversed.)
Foraminifera and ostracodes recovered primarily from siltstones reveal
that all of these units were deposited on the lower continental slope
(>1500 m) during the late Miocene and early Pliocene (10-4 Ma).
Mixed age and depth associations support a scenario similar to the
modern continental margin landward of the Peru-Chile trench, where deep
basins episodically receive sediments displaced from shallower depths.
Hence, although most of the gastropods are shelfal taxa, they were
transported by gravity flows onto the deep basin floor. Our samples
have yielded a microfauna that consists of approximately 350 species of
Foraminifera and 150 species of Ostracoda, which we are now in the
process of documenting. Representatives of this microfauna are shown
below. We have also examined core samples from numerous exploration
wells in the region that have revealed more of the geologic
section and provided us with some insight on the lateral extent of the strata
exposed along the coast.
View a poster about the coastal study
(Click once on any image below to magnify, then select your browser's back button or command to return to this page.)
| Rio Rapel area, northwest of Navidad |
Pta Alta-Pta Perro |
Punta Alta |
Punta Alta |
Punta Perro |
Turritella, P. Perro |
Matanzas |
Mostazal |
N of Rio Rapel |
| Arauco Peninsula, between Arauco and Lebu |
N of Pta Fraile |
N of Pta Fraile |
Punta Fraile |
Punta Fraile |
Pta Huenteguapi |
Pta Huenteguapi |
Foraminifera from the Chilean Neogene
Ostracoda from the Chilean Neogene
LAKE MERRITT
Several years after Samuel Merritt dammed this former tidal
slough in 1869 and began developing its surrounding wetland, flaws in
his "Jewel of Oakland" became unpleasantly evident as silt and algae
accumulated. Although part of it was designated as the nation's first
wildlife refuge (protecting more than 90 species of migrating
waterfowl), Lake Merritt also serves as a drainage basin for the
regional flood control system, receiving urban runoff from a 4,650 acre
watershed through 60 storm drain outfalls. Four culverted creeks drain
into this 145-acre lagoon from the east, while tidegates regulate flow
through a narrow channel connecting it with Oakland Inner Harbor and
San Francisco Bay. The lagoon is also polluted by illegal dumping of
substances toxic to marine life, such as paints, solvents, and oil. In
addition to mechanical harvesting of its widgeon grass, 1,000 to 7,000
pounds of trash are removed from Lake Merritt every month.
Anticipating its proposed remediation by the City of Oakland, Jere Lipps
and I realized there was an opportunity here to study before and after
effects on the microfauna. Several other studies have revealed
foraminiferal responses to pollutants, suggesting their utility as
environmental monitors. Dawn Peterson has joined our effort in
collecting and analyzing the bottom samples from Lake Merritt. Thus
far, we have identified 21 species of Foraminifera and 17 species of
Ostracoda, but our most recent collection is augmenting those numbers.
The more common species (shown below) are typical inhabitants of
hyposaline waters. Histologic staining reveals that the majority of our
assemblages from depths below one meter were devoid of living specimens
when collected. Most of the living specimens were recovered from water
depths less than a meter in the tidal inlet and along the margins of
the lagoon where and there are visible signs of life, such as algae and
mussels. Data obtained with a YSI 85D® water monitoring probe confirms
that stratification of the water column results in an unmixed deeper
layer characterized by low levels of dissolved oxygen. The decay of
organics on the bottom of the lagoon depletes the Oxygen and releases
hydrogen sulfide, which is evident in the stinky dark mud samples and
areas where bubbles rise to the surface. We suspect most of the deeper
assemblages were created by post-mortem transport from the shallow
margins, but we cannot rule out the possibility of intermittent mass
mortalities when dissolved oxygen levels drop below a tolerable
threshold. Unlike foraminiferal assemblages in the bay, those
in Lake Merritt often include malformed specimens, but surprisingly in lower relative abundance than typically reported from stressed environments where they have been linked to high
levels of contaminants, heavy metals, industrial pollution, and
domestic sewage.
(Click once on any image below to magnify, then select your browser's back button or command to return to this page.)
|
Views of Lake Merritt
Aerial View |
Lake View 1 |
Lake View 2 |
Lake View 3 |
Jere sampling |
Dawn sampling |
Tidal inlet |
Surface oil film |
Visitor |
Foraminifera from Lake Merritt
Malformed Ammonia tepida (first specimen shown above is normal)
Ostracoda from Lake Merritt
GALAPAGOS ISLANDS
Although the modern
microfauna of this famous archipelago has received a fair amount of
study, those in sediments that were uplifted and which are now exposed
along the edges of several islands have not been previously studied. It
includes Pleistocene foraminifera, ostracodes, and micromolluscs. With several
colleagues, I recently presented a poster about this project, and we are now preparing a manuscript for publication.
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FOSSIL WORM TUBES CONSTRUCTED OF FORAMINIFERA
Megan Flenniken (Stony Brook University), Jere Lipps, and I recently completed a study of unusual concentrations of foraminiferal tests that we interpreted to be the remnants of worm tubes. We obtained more than 70 specimens from the Miocene Monterey Formation near Carmel and Mission Viejo, California. Lithostratigraphic and biostratigraphic correlations firmly establish their ages as late middle Miocene near Carmel and early late Miocene at Mission Viejo; which means they are 9-13 million years old. The foraminifera indicate deposition occurred at bathyal depths. Surrounding strata are fine-grained, thin bedded and lack heavy bioturbation, features typical of the siliceous facies of the upper Monterey Formation and indicative of dysaerobic conditions. The foraminiferal concentrations are arranged in tube-like shapes similar to those constructed by some modern marine worms. Because agglutinated worm tubes readily disaggregate after the worm’s death, very few tubes have been found in the fossil record. In addition, although some modern worms construct their tubes using foraminiferal tests, the fossil record of this phenomenon to date is represented by a single specimen from the Lias (Lower Jurassic). The fossil tubes from the Miocene of California have closest affinity with the polychaete worm genus Pectinaria, which includes Recent species living at littoral to abyssal depths. Foraminiferal tests were likely the predominant sand-sized particles available to worms in the Miocene environments, thus the worms likely did not purposefully select foraminiferal tests. Low-oxygen conditions might have enhanced the potential for tube preservation, but subsequent leaching at the Carmel localities removed most calcareous test material from the sediment. Our specimens appear to be the first report of fossil pectinariids in the Western Hemisphere and only the second record of their occurrence in the Miocene.
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