NAPC 2001
June 26 - July 1 2001 Berkeley, California
Abstracts, Ph - Py
(5/22/01)
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EVEN DEEP TIME DEAD TELL TALES: DECOUPLING OF
TAXONOMIC AND ECOLOGICAL SIGNIFICANCE OF MASS EXTINCTIONS AND THE IMPLICATIONS
FOR MANAGEMENT OF MODERN DIVERSITY ISSUES
PHELPS, William T., and Mary L. Droser, Dept. of Earth Science, University
of California, Riverside, CA, USA
Fossil concentrations provide a proxy for faunal abundance and community
dominants, when depositional and taphonomic processes are accounted for.
Examination of large-scale shifts in faunal abundance and community dominants
is key to evaluating the extent of ecological change within an ecosystem.
To assess the ecological changes associated with the Late Devonian mass
extinction, Late Devonian and Early Mississippian fossil concentrations
from limestones of the western US were examined. These limestones formed
in a shallow-water, soft-substrate environment within a single depositional
basin under broadly similar environmental conditions.
Large-scale taxonomic changes in shallow marine fauna across the extinction
are well documented. However, no Bambachian Megaguilds are vacated, and
most groups recover in the Mississippian to near pre-extinction diversity
levels. This suggests that pre- and post-extinction communities may have
remained broadly similar. However, fossil concentration analyses show
a much different pattern. Devonian fossil concentrations are generally
polytaxic but dominated by brachiopods, while Mississippian fossil concentrations
are typically monotaxic (i.e., separate crinoidal, gastropod, and rugose
coral fossil concentrations) and dominated by crinoidal fossil concentrations;
the number of brachiopod concentrations decreases considerably. This shift
from brachiopod dominated polytaxic communities to crinoid dominated monotaxic
communities suggests there were large-scale shifts in the ecological structure
of this shallow marine community not predicted by the taxonomic data.
In contrast, the Late Ordovician extinction had a taxonomic loss similar
to the Late Devonian extinction but Silurian communities retained the
fundamental structure seen in the Ordovician. These results, coupled with
the loss of large-scale reefs at the Devonian extinction, thought to be
largely a result of the loss of stromatoporoids (Scrutton, 1988), point
to the importance of retaining keystone and dominant taxa in maintaining
ecosystem integrity.
NEW CAPRINID RUDISTS(BIVALVIA-HIPPURITACEA)
FROMEL DOCTOR AREA, OF THE QUERETARO STATE, OF CENTRAL MÉXICO
PICHARDO, Yolanda B., and Javier P. Aguilar, Facultad de Ciencias de
la Tierra, Universidad Autónoma de Nuevo León, México
El Abra Formation is exposed in large areas near the Municipality of
San Joaquin, in the State of Querétaro, in Central México.
This region is called Sierra Gorda because of its particular topography.
It belongs to the southeastern part of the Sierra Madre Oriental. The
reefal facies of this lithological formation is characterized by an abundant
fauna of caprinid and radiolitid rudists as the dominant groups. They
areassociated with gastropods, corals and other reefal organisms. Several
workers havemade extensive studies of El Abra Formation from this area,
principally the geology, tectonics, structural geology and mineral exploration
(Bonet, 1956; Segestrom, 1961; Enos, 1985; Tolson, 1998). On the contrary,
there are only afew articles with apaleontological approach.
The authors found in this location Caprinuloidea perfecta Palmer,
Coalcomana ramosa Boehm and Pacificaprina pyriformis Chartrousse
and Masse. This fauna is of Albian age, according to work by Alencáster
(1987, 1991, 1998); Alencáster and Aguilar (1995) in El Madroño,
the nearest area of El Abra Formation with the same reefal facies. The
first two species are reported for the first time from this locality,
while the last species isreported for the first timein Mexico and in America.
THE ROLE OF PERMINERALIZED PLANTS IN UNDERSTANDING
PLANT DIVERSITY, PHYLOGENY, AND PALEOENVIRONMENT: THE MIOCENE YAKIMA CANYON
CHERT
PIGG, Kathleen B., Dept. of Plant Biology, Arizona State University,
Tempe, AZ, USA
Like the middle Eocene Princeton chert of southern British Columbia,
the Yakima Canyon chert of central Washington State contains a diverse
permineralized flora. This flora is of middle Miocene age (15.6 Ma) and
in contrast to the Princeton chert, contains only temperate floral elements.
Many of these are closely related to modern plants at several infrageneric
levels, including section, subsection and even species. Included are the
osmundaceous fern Osmunda wehrii (Osmunda subgenus Osmunda,
Osmundaceae), Pinus foisyi, a pine of the California closed cone
pine group (Pinus subgenus Pinus, section Pinus,
subsection Oocarpae, Pinaceae), the white oak Quercus hiholensis
(Quercus subgenus Quercus, section Quercus, Fagaceae),
and the fern Woodwardia virginica (Blechnaceae), which is essentially
identical to the modern Virginia chain fern of the Atlantic coastal plain.
Unlike compression floras of the same age that are identified primarily
on the basis of leaf morphology, the Yakima Canyon flora shows details
of fruit and seed anatomy, and thus provides both an independent means
for taxonomic assignment and a much greater degree of taxonomic resolution.
Additional floral elements currently under study include both "typical"
middle Miocene families (such as Taxodiaceae, Altingiaceae, Vitaceae,
Cornaceae, and Rosaceae), as well as fruits and seeds that cannot be placed
easily within modern genera and probably represent extinct taxa.
THE BIRTH OF THE MEDITERRANEAN SEA FROM A BIOGEOGRAPHIC
PERSPECTIVE
PILLER, Werner E., Institute for Geology and Palaeontology, University
of Graz, Austria; Mathias Harzhauser and Fred Roegl, Natural History Museum,
Vienna, Austria; Oleg Mandic, Institute for Palaeontology, University
of Vienna, Austria; James H. Nebelsick, Institute for Geology and Palaeontology,
University of Tübingen, Germany; Fritjof Schuster, Fritz F. Steininger,
and Ulrike Wielandt-Schuster, Senckenbergmuseum, Frankfurt/Main, Germany
The closure of the Tethyan Seaway is a major palaeogeographic and biogeographic
incision and marks the origin of the Mediterranean as a biogeographic
unit. It significantly changes global equatorial ocean water circulation
by blocking the seaway between the Indo-Westpacific and the Mediterranean
and makes exchange of marine biota between these bioprovinces impossible.
However, it enables terrestrial organisms to move from Africa to Eurasia
and vice versa. To trace the closure and related effects, in a multidisciplinary
approach Oligocene and Early Miocene sections were studied in Central
Iran (Esfahan-Sirjan Basin, Qom B.), the Zagros Mountains, Turkey (Mut
B., Sivas B.), Greece (Mesohellenic Trough), and Egypt (Suez area). These
well-dated sections clearly show that a continuous marine connection between
the western Iranian area and the eastern Mediterranean existed up to the
Late Burdigalian. Detailed analyses of various biota (corals, foraminifera,
gastropods, bivalves, echinoderms) clearly furnish evidence that the Central
Iranian basins, as key-area between the Western Indo-Pacific and the Eastern
Mediterranean, display a Mediterranean character throughout the Oligocene
and Early Miocene. Although a marine connection was present until the
Late Burdigalian, exchange of biota became more and more limited during
the Aquitanian and Early Burdigalian. Similarities, for example, to Pakistanian
faunas are high during the Oligocene decreasing, however, distinctly during
the Early Miocene. Only a few Pakistanian species reach west as far as
the Qom Basin. However, some of the Burdigalian species reported from
Iran are absent in Europe and may be a hint to an Indo-Pacific influx
in an overall Mediterranean fauna. Indo-Pacific gastropod species, known
from Burma or Java are well represented as far west as Pakistan, but did
not extent to the Mediterranean. Thus the melting pot between Indic and
Mediterranean gastropod faunas was located in the Pakistanian area during
the Oligocene, while a takeover by Indo-Pacific gastropods occurred during
the Early Miocene.
SIMULATIONS AND THEORETICAL MORPHOLOGY OF TRACE
FOSSILS
PLOTNICK, Roy E., Dept. of Earth and Environmental Sciences, University
of Illinois at Chicago, Chicago, IL, USA
Trace fossils represent the preserved interactions of trace making organisms
with their environment. The form of traces should result from complex
interactions among the organism's morphology, the behavior being carried
out, the organism's perception of the environment, and the heterogeneity
of the environment. Existing mathematical models for the biological formation
of traces have tended to focus on a limited repertoire of behaviors, such
as grazing. They do not include realistic patterns of environmental heterogeneity,
differences in perception, or multiple behavioral responses. In addition,
there have been virtually no attempts to model three-dimensional traces
or traces that branch or anastomose. I will discuss two new approaches
to modeling trace fossils.
New models for grazing and crawling traces are built on current research
by ecologists into animal movement patterns and their interaction with
environmental heterogeneity. These models explore the interactions of
alternative spatial patterns of environmental heterogeneity with different
perceptions and behavioral responses to it. They have the potential for
suggesting how behavioral patterns for a given trace-making organism might
change as a function of environmental differences, such as resource distribution.
This could be a useful tool for determining such patterns of spatial heterogeneity
in ancient environments.
Models for geometrically complex traces are based on recent developments
in the computer-based study of morphogenesis. L-systems and related methods
can be used for the generation of branching and three-dimensional theoretical
morphologies. L-system descriptions can be quite complex and can incorporate
realistic concepts of growth, including external environmental factors
and signal transmission. They have been used previously for the production
of simulated plants of startling realism. By altering the parameters used
to generate the simulated fossils, a theoretical morphospace for trace
morphology could be constructed.
MORPHOLOGY, STRUCTURE, AND COMPOSITION OF TROPICAL
INTERTIDAL AND SUPRA-LITTORAL MICROBIAL MATS
POETKER, Shelene, Dept. of Integrative Biology, University of California,
Berkeley, USA
Microbial mats covering a partially inundated mudflat on the island of
Moorea, French Polynesia were studied during October and November 2000.
Initial surveys indicated the presence of seven phenotypes. In order to
test this classification and to characterize and describe the mats, 33
mats encompassing all seven types were examined using light microscopy.
The mats were dominated by cyanobacteria belonging to the genera Lyngbya
and Microcoleus. Other cyanobacteria genera including Oscillatoria,
Phormidium, Xenococcus, and Chroococcus as well as
unidentified cyanobacteria and diatoms were also present. Species dominance
and frequencies differed between the pre-defined types. All mats were
vertically stratified, although to different degrees, and thickness ranged
from 1 mm to 30 mm. Although the number of laminations differed, most
mats had an upper green gelatinous layer and a lower reddish layer. A
PCA analysis comparing the environmental and compositional data for 27
mats challenged the pre-defined categories, suggesting that the mats are
better grouped into four categories. These results along with a cluster
analysis and findings in the literature indicate the presence of two primary
types: a Smooth/Reticulate mat and a Blister mat, as well as two types
along the periphery of these in various stages of lithification. Extensive
extracellular polymer production was present in all mat types, and allowed
the mats to bind sediment. Grazing and bioturbation were present in most
mat types, and consisted primarily of nematodes and amphipods. Average
salinity of the groundwater was 6.8% and temperatures ranged from 27.548°C,
indicating an extreme hypersaline environment similar to those characterized
for microbial mats in other tropical regions.
HIGH MORPHOLOGICAL DIVERSITY IN NEOPROTEROZOIC
VASE-SHAPED MICROFOSSIL ASSEMBLAGES FROM THE CHUAR GROUP, GRAND CANYON;
COMPARISONS WITH MODERN TESTATE AMOEBAE
PORTER, Susannah M., Dept. of Organismic and Evolutionary Biology, Harvard
University, Cambridge, MA, USA; and Ralf Meisterfeld, Dept. of Biology
II, Rheinisch-Westfälische Techn. Hochschule, Aachen, Germany
Recent studies of newly discovered vase-shaped microfossil (VSM) assemblages
from the >742 ± 6 Ma Chuar Group, Grand Canyon, suggest affinities
with testate amoebae. These fossils thus extend the stratigraphic range
of testate amoebae by ~500 million years, and provide the earliest body
fossil evidence for heterotrophic protists in marine ecosystems. Further
investigation of these assemblages reveals that VSMs exhibited a much
higher degree of morphological diversity than previously documented. Using
the taxonomy of modern testate amoebae as a guide, we have provisionally
identified nine new species of Chuar Group vase-shaped microfossils that
augment the eight species already described globally. Comparisons with
modern testate amoebae indicate that many of the test characters exhibited
by this modern group were already present 742 Ma. Furthermore, character
combinations in specific VSM taxa closely approximate those of particular
modern testate amoeban taxa, including species in the families Euglyphidae,
Trigonopyxidae, Centropyxidae, and Arcellidae. This provides further support
for the view that many VSMs represent lobose and filose testate amoebae,
and suggests that these groups not only originated but also had diversified
during Neoproterozoic time.
INVERTEBRATE FOSSILS OF THE WILSON GROVE FORMATION
(LATE MIOCENELATE PLIOCENE), SONOMA COUNTY, NORTHERN CALIFORNIA
POWELL, Charles L., II, U.S. Geological Survey, Menlo Park, CA, USA;
and James R. Allen, Dept. of Geology, San Jose State University, San Jose,
CA, USA
Fossil mollusks from the Wilson Grove Formation (WGF) represent shallow
to deep marine environments and range in age from late Miocene to late
Pliocene. The WGF outcrops from Petaluma north to northern Santa Rosa,
and west of the Rogers Creek fault to the coast.
Wilson Grove Formation rocks representing shallow water environments
occur along the eastern margin of the outcrop area at Meacham Hill and
along the northern margin at River Road and the type locality at Wilson
Grove. At Meacham Hill these shallow water deposits suggest a brackish
bay environment, whereas at River Road and the type locality at Wilson
Grove fossils suggest euhaline conditions. Mollusks from the River Road
area also suggest water temperatures warmer than today along the adjacent
coast. Deep water environments occur to the southwest along Estero San
Antonio. Other outcrops of the WGF do not have enough taxa present for
accurate biogeographic or environmental determination.
Outcrops of the WGF to the south suggest an earlier age than outcrops
to the east and north. The late Miocene Roblar Tuff occurs at Steinbeck
Ranch in the southern part of the outcrop area, whereas the occurrence
of the bivalve mollusks Macoma addicotti (Nikas) and Nuttallia
jamesii Roth and Naidu suggest a late Pliocene age for the northern
outcrops at River Road. This age is suggested by the co-occurrence of
these bivalve taxa at River Road and in the sea cliffs at Capitola, Santa
Cruz County (Purisima Formation) where they have been dated using high
resolution diatom biostratigraphy and magnetic polarity zonation.
These data suggest an overall pattern for the WGF of older and deeper
to the south and younger and shallower to the north. Fossils in the eastern
part of the outcrop area represent shallow water but are not age diagnostic.
USING CONSTRUCTIONAL DATA TO DETECT CONVERGENCE:
AN UNDERUTILIZED APPROACH TO STUDYING ADAPTATION IN THE FOSSIL RECORD
PRICE, Rebecca M., Dept. of Geophysical Sciences, University of Chicago,
Chicago, IL, USA
Although adaptation has always been a major focus of evolutionary biology,
we have only recently begun to study it thoroughly with the advent of
the comparative methods. Rigorous studies of the effects of adaptation
through geologic time are still relatively rare, perhaps because comparative
methods require robust phylogenetic hypotheses, which are not available
for most taxa over long time intervals. The Fasciolariidae (Neogastropoda:
Mollusca), for example, is an appropriate taxon for studying the dynamics
of adaptation because it is long-lived (reputedly originating in the Valanginian
and still extant), and because it exhibits variation in the shape of columellar
folds, prominent ornamentation on the aperture of many neogastropods traditionally
used in systematics and assumed to be adaptive. A thorough cladistic analysis
of the family cannot be conducted without extensive taxonomic revision
because the species and genera are poorly defined, and there are few reliable
characters that may be synapomorphies. If columellar folds are adaptive,
however, it is reasonable to predict that similar fold morphologies evolve
repeatedly in different clades, assuming that columellar folds that are
constructed differently represent independent derivations. Here, I test
the hypothesis that an analysis of growth lines (observed through a combination
of acetate peels and thin sections) will reveal multiple ways of constructing
similar columellar fold morphologies in the Fasciolariidae and other high-spired
gastropods. I use data describing the construction of the folds (sensu
Miller, 1999) to detect convergence in five categories of columellar fold
morphology. Tojo and Ohno (1999) showed that the folds in the potamidid
Terebralia palustris are formed after the rest of the columella,
but my preliminary analyses show that the folds of the fasciolariid Leucozonia
nassa are constructed as the columella grows.
MAGNETIC STRATIGRAPHY OF THE EOCENE-OLIGOCENE
EUGENE/FISHER FORMATIONS, WESTERN
OREGON: IMPLICATIONS FOR THE "TERMINAL EOCENE EVENT"
PROTHERO, Donald R., Dept. of Geology, Occidental College, Los Angeles,
CA, USA; and Gregory J. Retallack, Dept. of Geology, University of Oregon,
Eugene, OR, USA
The floras of the Eugene and Fisher Formations in the Eugene area of
west-central Oregon were crucial to Wolfe's (1978) claim of a major cooling
and drying episode that he labeled the "Terminal Eocene Event."
Recent magnetostratigraphic investigations, along with new radiometric
dates, help to constrain the age of this floral event. Most of the available
sections in the Eugene, Coburg, and Goshen area were sampled, and analyzed
on a cryogenic magnetometer, using both thermal and alternating field
demagnetization. The magnetization is largely held in magnetite and yields,
single component primary magnetizations, which pass both a fold test and
reversal test. There are three tuff horizons found throughout the area,
which help correlate the sections, and calibrate them as well. The lowest
(Bond Creek tuff) yields a date of 35.9 Ma, and the upper tuff yields
a date of 31.8 Ma; the middle tuff is currently undated. Based on these
dates, we correlate the type Eugene marine strata with Chron C13r (33.534.5
Ma, latest Eocene), the megathermal Goshen flora with late Chron C13r-early
Chron C13n (33.034.0 Ma, earliest Oligocene), the cooler-adapted
Coburg flora with Chron C13n (33.033.5 Ma, early Oligocene), and
the Willamette flora with Chron C12r (31.033.0 Ma, or early and
late Oligocene). These dates suggest that Wolfe's "Terminal Eocene
Event" is actually earliest Oligocene (about 33.2 Ma), consistent
with other global climatic indicators that show the major Antarctic cooling
event occurred in the earliest Oligocene, not at the Eocene/ Oligocene
boundary. In addition, recent reassessment of the paleobotanical evidence
suggests that it was not as extreme a climatic event as Wolfe (1978) once
suggested, although it was still very abrupt (less than half a million
years).
DEVELOPMENT OF MICROBIAL FABRICS IN EARLY TRIASSIC
OCEANS
PRUSS, Sara B., and David J. Bottjer, Dept. of Earth Sciences, University
of Southern California, Los Angeles, CA, USA
The Early Triassic represents a period of recovery from the largest extinction
in the history of life, the end-Permian mass extinction. During this time,
marine microbial fabric development has been documented globally. Research
by Kershaw et al. (1999) shows the occurrence of what may be a microbialite
crust at the Permian-Triassic boundary in South China. This crust is suggested
to have been formed by a disaster biota that thrived in the presence of
unusual oceanic conditions occurring at the P-T boundary. The absence
of grazers has also been cited as increasing the potential for such microbial
development. Recent work by Lehrmann (1999) shows the presence of biostromes
and microbial mounds from the Lower Triassic Nanpanjiang Basin in South
China. These biostromes and mounds occur in two horizons: one in Griesbachian
strata and one in Smithian-Spathian strata. In some places, these beds
attain thicknesses of 15 meters suggesting that these microbial features
occurred as reefs.
Stromatolites and thrombolites have also been reported as mass extinction
disaster forms from late Early-Triassic-age strata in the Western United
States (Schubert and Bottjer, 1992). These microbial structures from the
Virgin Limestone Member of the Moenkopi Formation have been recently reinvestigated
to determine if they represent true reefs. In places microbial mounds
occur as isolated patch reefs, although elsewhere they coalesce to form
tabular biostromes. These mounds are an agglomeration of smaller subunits
that have wavy laminations and thrombolitic textures. Measurements on
isolated mounds show that they attained a relief of 12 meters above
the seafloor. These results, together with those from previous studies,
demonstrate that small reefs, although rare, can be found throughout the
early Triassic. These primarily microbial constructions represent the
earliest reef systems of the Mesozoic.
EVOLUTIONARY FABRIC OF OSTRACODE FAUNAS FROM
THE LATE CRETACEOUS (SANTONIAN-MAASTRICHTIAN) OF THE US GULF COASTAL PLAIN:
RELATIONSHIP WITH SEA LEVEL DYNAMICS
PUCKETT, T. Markham, Dept. of Geological Sciences and Center for Sedimentary
Basin Studies, University of Alabama, Tuscaloosa, AL, USA
Ostracodes and planktonic foraminifera were collected from two composite
reference sections (CRS) in the marine Upper Cretaceous deposits of the
US Gulf Coastal Plain, one in central Alabama and one in eastern Mississippi.
One hundred eight ostracode taxa were recognized in the two CRSs, and
their ranges were analyzed using graphic correlation. Planktonic foraminifera
were used for chronostratigraphic control. These data are the record of
evolution of these faunas for the interval between 86 and 69 Ma.
Three depositional sequences are recognized in these Upper Cretaceous
deposits. The two older sequences (Santonianearly Campanian UZAGC-3.0
sequence, and the Campanian UZAGC-4.0 sequence) were deposited in a greenhouse
climate, characterized by very slow rates of sea level change, whereas
the younger sequence (Maastrichtian UZAGC-5.0 sequence) is of much shorter
duration and was possibly controlled by glacial activity (icehouse).
The coastal onlap and offlap clearly affected the community structure
and rate of evolution of the ostracode faunas. High rates of faunal turnover
are observed around sequence boundaries, even though the boundary between
the two older sequences (UZAGC-3.0 and UZAGC-4.0 sequences) is a Type
II boundary and displays an insignificant hiatus. Although the high number
of originations at the base of the section reflects initial quantification
of incipient taxa, relatively high rates of origination occur in the lower
part of the UZAGC-3.0 sequence. High rates of both originations and extinctions
occur around the sequence boundary. Subsequent to this faunal turnover
event, community stasis is observed by low rates of both origination and
extinction. This community was stable for approximately three million
years, is characterized by low diversity, and includes taxa adapted to
living in an extremely fine-grained chalky substrate. Faunal turnover
rates again increase near the boundary between the UZAGC-4.0 and UZAGC-5.0
depositional sequences.
PLIO-PLEISTOCENE DIATOMS OF ALASKA: APPLICATION
TO HIGH-RESOLUTION PALEOENVIRONMENT RECONSTRUCTION
PUSHKAR, Vladimir S., Pacific Institute of Geography FEB RAS, Vladivostok,
Russia; Marina V. Cherepanova, Institute of Biology and Soil Science FEB
RAS, Vladivostok, Russia; and Julie K. Brigham-Grette, Dept. of Geoscience,
University of Massachusetts, Amherst, MA, USA
The Gubik Formation of Arctic Alaska, Cape Blossom and Hotam Inlet Formations
of western Alaska consist of at least six superposed marine, glaciomarine
and terrestrial transgressive sequences. The diatom data recorded in these
sequences, which include the Arctic Alaska Pliocene marine Nulavik, Killi
Creek, Tuapaktushak beds, the Pleistocene Karmuk beds, and the Pleistocene
marine Anvilian beds, the glaciomarine Baldwin Silt and periglacial Selawik
beds (Baldwin Peninsula), allow us to demonstrate high-resolution paleoecological
and paleogeographic reconstructions. Plio-Pleistocene extinct species,
as well as other forms that make their first appearance near the Plio-Pleistocene
boundary were used for age determinations. The studied deposits of the
Nulavik, Killi Creek and Tuapaktushak beds correspond to the middle Neodenticula
kamtschatica-Neodenticula koizumii Zone (3.43.1 Ma),
the lower Thalassiosira convexa Zone (2.52.4 Ma),
and the lower Pyxidicula zabelinae Zone (2.22.0 Ma), respectively.
The Diatom sequences are clear evidence that the Late Pliocene was punctuated
by at least three periods of high sea level, when conditions were dramatically
warmer than now. These units are unconformably overlain by Karmuk deposits
(analogy of Anvilian and Baldwin Silt beds), with index-species of the
middle Proboscia barboi Zone (0.430.38 Ma) from a younger
high sea level event containing diatoms consistent with dates to warm
marine isotope stage 11. Glaciomarine and periglacial sedimentation (Baldwin
Silt and Selawik beds) was initiated during the end of the stage 11 transgression
and continued into cold stage 10. High-latitude glacier growth during
a global interglacial period was facilitated by warm surface waters on
flooded continental shelves and limited regional sea ice cover (Baldwin
Silk time). These data are useful to clear understand the influence Arctic
diatoms on the diatom assemblages of the western Pacific Arc-Island System.
Russian Foundation for Basic Research (Grant 00-05-64837) supported this
work.
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