NAPC 2001

Abstracts, Uc - Wa
(5/23/01)

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GRAPHOGLYPTID TRACE FOSSILS: THEIR ETHOLOGY, ECOLOGY END EVOLUTION

UCHMAN, Alfred, Institute of Geological Sciences, Jagiellonian University, Krakow, Poland

Graphoglyptids are patterned, mainly meander-, star-, and net-shaped trace fossils preserved almost exclusively in semi-reliefs on soles of turbidites or tempestites. Analysis of their morphology allows reconstructing complicated burrow systems composed commonly of various mazes, galleries, and shafts located in shallow tier in sediments. Graphoglyptids are characteristic component of the Nereites ichnofacies, which is typical of deep-sea turbiditic deposits. Rarely, they occur also in intra-shelf storm-dominated basins. Record of graphoglyptids depends largely on preservation influenced mostly by delicate scouring and casting. Their occurrence on soles of isolated event beds proves that graphoglyptid burrows are common in pelagic environment, but their preservation as trace fossils is almost impossible.

Graphoglyptids are interpreted as burrows of unknown invertebrates, in which they farm microorganisms (category agrichnia). Their abundance is related to general shortcoming of food in deep-sea environments. Nutrients from seasonal plankton blooms are quickly settled in fecal pellets on the deep-sea floor. Probably, tracemakers prolong use the food abundance from this source for the starvation periods by the agrichnial activity. Graphoglyptids are most abundant in well-oxygenated deposits in oligotrophic conditions.

Graphoglyptid trace-makers originated in Early Cambrian shallow-marine settings and migrated to the deep-sea probably in the Middle Cambrian. Generally, graphoglyptid diversity increased very slowly during most of Phanerozoic, and rapidly increased during Cretaceous and Paleogene. The rapid increase is related to changes in pelagic environments, especially to evolution of plankton, increase in nutritional competition, and improvement of oxygenation of the deep-sea floor. Particular ichnogenera display individual evolutionary trends. For instance, occurrence of miniature ichnospecies, since Cretaceous and giant ichnospecies since Paleogene characterize Paleodictyon.

TIME-SPACE CHANGE OF SURFACE SEA WATERS AFTER CA. 20 KA IN THE KUROSHIO SOURCE REGION, PACIFIC OCEAN: CONSTRAIN FROM PLANKTONIC FORAMINIFERA

UJIIE, Yurika, Ocean Research Institute, University of Tokyo, Tokyo, Japan

The Kuroshio Current influences the distribution and condition of surface water masses such as the western boundary current in the North Pacific Ocean. It is very important to know how the surface water masses have changed, because they influence the climate of the whole North Pacific region. After diverging from the North Equatorial Current, the Kuroshio Water flows into the Okinawa Trough and strengthens its nature, so that the Ryukyu Arc region is regarded as the Kuroshio source region. Ujiie and Ujiie (2000) demonstrated that modern planktonic foraminifera are characteristically divided into four groups: Kuroshio, subtropical water, coastal water and rather cold water groups. Fifteen piston cores were collected from the Ryukyu Arc region and dated by planktonic d¹⁸O stratigraphy, AMS ¹⁴C measurements, and tephrachronology down to ca. 20 ka. Using these cores, I made a detailed planktonic foraminiferal analysis by comparing the analytical results with the modern faunas. The most remarkable conclusion is that the Kuroshio Current greatly changed twice; once during the last glacial period and then from ca. 4500 to 3000 yr BP. The former case was associated with drastic cooling as shown by decreasing d¹⁸O and by dominant occurrence of the cold water group of planktonic foraminifera. However, the main path of the Kuroshio Current could not enter the Okinawa Trough because of a geographic barrier between Taiwan and the southern Ryukyu Arc. In the latter case however, no cooling signal is recognized. Instead, the coastal water type of planktonic foraminifera prevailed over the Okinawa Trough and the central water type became dominant over the central and northern Ryukyu Arc region suggesting a diminishing of the Kuroshio Current.

AVIAN MOLECULAR CLOCKS AND NEORNITHINE DIVERGENCE TIMES

VAN TUINEN, Marcel, Dept. of Biological Sciences, Stanford University, Stanford, CA, USA; and S. Blair Hedges, Dept. of Biology and Institute for Molecular Evolutionary Genetics, Penn State University, University Park, PA, USA

Here, we provide a review of the available avian clock studies and their methods. Consensus is found among most studies in showing a Cretaceous origin of the major clades of modern birds. This suggests that major fossil gaps exist for the early neornithine evolutionary history. However, these clock studies have either employed limited taxon sampling or small sequence data sets. Use of a sequential calibration in species-rich avian molecular data sets allow timing of additional events in the evolutionary history of modern birds. The results agree with earlier studies that the major clades of modern birds originated in the Cretaceous.

LOWER PALEOZOIC MICROPHYTOPLANKTON BIOGEOGRAPHICAL DIFFERENTIATION: APPLICATION TO TERRANE ANALYSIS AND PROVENANCE STUDIES IN CENTRAL EUROPE

VECOLI, Marco, Institute für Geologische Wissenschaften MLU Halle/Wittenberg, Domstrasse 5, D-06108, Halle (Saale) Germany

New data on paleogeographic and chronostratigraphic distribution of Cambrian-Ordovician acritarch assemblages from northern Gondwana and the Baltic region, permit a re-definition of the spatial and temporal evolution of microphytoplankton provincialism. From Late Cambrian through early Arenig times, the northern margin of Gondwana and the East European Platform shared essentially similar microphytoplankton assemblages. From the late Arenig, acritarch assemblages clearly differentiated into a middle- low-latitude, warm to temperate-water microflora primarily diffused in the East European Platform, and a high-latitude, cold-water microflora characterizing the northern Gondwana margin. Accordingly, starting from from the late Arenig, acritarchs can be used as reliable palaeogeographical indicators.

The Trans European Suture Zone (TESZ) represents the complex region of transition between the stable Precambrian crustal domains of the East European Platform (EEP), and the younger mobile belts of the Paleozoic Europe. The origin of the TESZ is primarily related to the closure of the Tornquist Ocean and the amalgamation of a series of crustal blocks ('microcontinents') of peri-Gondwana derivation to the southwestern margin of the EEP during Caledonian times.

Palynological analysis of subsurface Cambrian-Ordovician clastic sequences across the TESZ permitted the precise identification of the northern boundary of the Perigondwana-derived Avalonia terrane and the timing of its amalgamation to the Baltic Craton. Reworked early Ordovician acritarchs of clear Perigondwanan affinity were recovered in fine clastic sediments of latest Ordovician–earliest Silurian age deposited on the southwestern margin of Baltica. These reworked acritarchs demonstrate a clastic input of Avalonian provenance onto the flexured Baltic Shield following the development of a collisional belt between Avalonia and Baltica. Consequently, it is possible to date the Avalonia-Baltica collision to latest Ordovician (Ashgill) times.

APORRHAID GASTROPODS OF LATEST CRETACEOUS AGE FROM THE UPPER PART OF THE BARTON CREEK FORMATION, BELOW CHICXULUB EJECTA BANKET IN SOUTHERN MÉXICO

VEGA, Francisco J., and Maria del Carmen Perrilliat, Instituto de Geología, UNAM, México; Adriana Ocampo, NASA Headquarters, Washington, DC, USA; and Kevin Pope, Geo, Eco Arc research, Washington, DC, USA

Chicxulub impact ejecta deposits crop out in northern Belize and southeast Mexico (Quintana Roo). The lower Maastrichtian crab Carcineretes planetarius Vega et al. was previously reported from the Barton Creek Formation in Albion Island, Belize, approximately 20 meters below the base of the Albion Formation, which includes the ejecta blanket deposits. Recent prospects on Mexican outcrops of the uppermost part of the Barton Creek Formation yield several specimens of a new species of Aporrhais. This genus of gastropod is known from the Lower Cretaceous to the Recent. Maastrichtian representatives of this gastropod have been reported from Germany, India, and the Western Interior. The most similar species to this one is A. granulosa Muller from the Aachensands of Germany. However, this species is different from the new one of Quintana Roo in that it lacks a third carina on the body whorl, and the granules are not as strong as in our specimens. A. biangulata Meek and Hayden from the Pierre Shale of Montana do not have any granules on their carina, which are two and smooth. This is the first report for this genus from the Gulf Coast and the Caribbean. Also, from its stratigraphic position 20 meters above the lower Maastrichtian beds with C. planetarius and 20 centimeters below the K/T boundary, it is found in the latest deposits of the Barton Creek Formation. Numerous bivalves and other gastropods have been found associated with the new species and a systematic report is in preparation. There seems to be differences between this assemblage and the one in which the carcineretid crab was found. This may be due to stratigraphic position, as a calcareous, shallow marine and lagunar paleoenvironments seem to have prevailed in this region up until the bolide impact. Based on the size and morphology of the Cretaceous and Cenozoic representatives of Aporrhais, we propose that some evolutionary trends for this genus are: development of a third carina on the body whorl, presence of granules on these carina, development of a medial ridge on the spire whorls and increase of body size.

PALEONTOLOGY AND GEOLOGY OF THE ATOTONILCO EL GRANDE FORMATION (BLANCANO) HIDALGO, MEXICO

VELASCO-DE LEÓN, P. Carrer, Biology, Facultad de Estudios Superiores Zaragoza, UNAM, México; Javier Arellano-Gil, Facultad de Ingenieria, UNAM, México; A. Silva-Pineda, Instituto de Geología, UNAM, Mexico

With the interest of studying some of the lacustrine sequences of the Cenozoic of the center of Mexico, we studied the Atotonilco el Grande Formation, as it is exposed in Santa María Amajac, Hidalgo. Atotonilco el Grande Formation has a thickness of 550 m, measured in a composite section. The basal 350 m correspond with a clastic lacustrine environment, influenced by volcanic activity and the remaining upper 200 m corresponds with a lava wash. The basal portion is exposed to the northwest of Santa Maria Amajac and in Sanctorum. In Santa Maria Amajac it is composed of moderately compacted erratically classified conglomerates, where rounded fragments of andesite and basalt prevail, with a sandy matrix. In Sanctorum Valley, in constrast, the sequence is composed of fine-grained sandstones, limestones, shales and some gypsum horizons in strata that vary in thickness from to 5­7 cm; some strata have calcareous cement. In this sequence, leaves of Rhamnaceae, Platanacea, Salicaceae, stems of Equisetales, as well as girogonitos of Caroficeas and leaves of gymnosperms have been collected. The fauna is represented by two fish types, gastropods of the genus Planorbis, ostracods, insects, and vertebrate remains. Based on the associated fauna and small quantity of plant fossils, this locality is interpreted as the deepest zone of the paleolake. In contrast, in Santa Maria Amajac only leaves of the angiosperm families Platanaceae, Salicaceae, Rosaceae, Asteraceae and Fagaceae have been collected. Members of the two first families suggest the presence of riparian vegetation. In conclusion, lithological characteristics of immature sediments in Santa Maria Amajac strata, tabulates and parallel lamination in Sanctorum are interpreted such that the lacustrine sequence corresponds to two facies.

EDGE-DRILLING: HISTORY AND DISTRIBUTION OF A NOVEL METHOD OF PREDATION

VERMEIJ, Geerat J., Dept. of Geology, Universiy of California, Davis, CA, USA; and Peter D. Roopnarine, California Academy of Sciences, San Francisco, CA, USA

Edge drilling is a form of predation in which the predator (a muricid or naticid gastropod) drills a hole at a point on the commissure between the closed valves of a bivalved animal. Previous studies of drilling have largely ignored edge drilling. We have investigated the incidence and location of edge-drills in venerid bivalves. In the living biota, edge drilling is common only in shallow water. Wall-drilling (penetration through one valve) has been known from latest Proterozoic time onward, but edge drilling seems to have been extremely uncommon before the Miocene. Beginning in latest Neogene time, edge drilling became quantitatively important as a form of predation in thick-shelled venerids on both coasts of tropical America and in other warm-temperate to tropical regions. Holes are concentrated on the posteroventral margins of the valves. We speculate that edge drilling is faster than wall drilling, and may therefore be advantageous in environments where predators face high risks while feeding. Phylogenetically, edge drilling appears to be a derived condition relative to wall-drilling in both naticids and muricids.

THE RULEBOOK IS REWRITTEN: EDIACARAN AND CAMBRIAN GLOBAL BIODIVERSITY PATTERNS

WAGGONER, Ben M., Dept. of Biology, University of Central Arkansas, Conway, AR, USA

The late Proterozoic was marked by several glacial episodes. While the precise number and extent of these glaciations is not settled, glacial conditions were unusually widespread at this time, possibly covering the entire Earth (the "Snowball Earth" hypothesis). The well-known Ediacara biota first appeared during an interglacial interval, and diversified soon after the last Proterozoic glaciation. It would seem reasonable that the diversification of the Ediacara biota might have been influenced by Precambrian glaciations. For example, it might be hypothesized that the paleoequatorial region included refugia for early Ediacaran lineages during glacial episodes. If the Ediacara organisms were photosynthetic, as some workers have proposed, then the most diverse biotas might have been in regions with the most sunlight and/or the least seasonality. All of these might lead us to hypothesize that Ediacaran organisms showed a latitudinal diversity gradient—a pattern that is very well documented for many marine taxa today—even if the Earth's thermal gradient during Ediacaran time was mild.

I created a database of the presence and absence of Ediacaran organisms, and compared it with paleolatitude using several paleotectonic reconstructions. I also created a similar database of Early Cambrian trilobite occurrences. Simple counts of the number of genera reveal no latitudinal gradient for the Ediacara organisms, even when various means of correcting for sampling and facies differences are used. Early Cambrian trilobites show a definite gradient, with the most diverse biotas close to the paleoequator; gradients have also been reported for archaeocyathids and other Cambrian taxa. I propose that this reflects a very different ecological "rulebook" in Ediacaran ecosystems, and may reflect a radically different way of life for most of the Ediacaran organisms. Results of a cladistic biogeographic comparative study will be presented in a search for subtler biogeographic patterns in the data.

PATTERNS OF GENERAL CONVERGENCE AMONG PALEOZOIC GASTROPODS

WAGNER, Peter J., Dept. of Geology, Field Museum of Natural History, Chicago, IL, USA; and Douglas H. Erwin, Dept. of Paleobiology, National Museum of Natural History, Washington, DC, USA

Iterative evolution of general shell forms is well known among gastropods, with many of the basic shell types reflecting function and ecology rather than common ancestry. However, these basic shell forms have provided the basis for much of higher taxonomy, especially among Paleozoic clades. Here we explore temporal and phylogenetic patterns of morphospace occupancy within a general shell form space among over 600 early (latest Cambrian­Devonian) gastropods. We scored species for the following features: two coiling parameters (Raup's translation and distance of inner margin from coiling axis); gross aperture shape; long-axis of apertural orientation; apertural inclination; left-right symmetry of the aperture; slit presence; siphon presence; and, base shape. Almost all of these features represent compound traits insofar as different combinations of specific shell features can produce the same general feature.

General shell characters create clusters similar to traditional classifications. However, phylogenetic estimates using specific shell features and stratigraphic data indicate that these clusters are highly polyphyletic. For example, macluritiforms (nearly-planispiral with flat bases) appear at least seven times, trochiforms (moderate spire height, inclined apertures, round aperture shapes) appear at least eight times, and subulitiforms (high spired with highly asymmetrical apertures and siphons) appear at least five times. However, the clusters not phylogenetically random: 6 of 7 macluritiforms and 7 of 8 trochiform groups come from the euomphaloid clade whereas all five subulitiform groups come from the murchisonoid clade. Also, Monte Carlo tests reject the hypothesis that phylogeny alone explains species distributions in the general character space. These results corroborate two ideas: (1) general forms are largely shaped by functional biology; and (2) similar functional morphologies evolved repeatedly.

DOES THE RODENT FOSSIL RECORD PROVIDE EVIDENCE FOR LINEAR RATES OF MOLECULAR EVOLUTION?

WALTON, Anne H., Pratt Museum of Natural History, Amherst College, Amherst, MA, USA; Read D. Porter, Dept. of Geology, Amherst College, Amherst, MA, USA; and Ronald M. Adkins, Dept. of Biology, University of Massachusetts, Amherst, MA, USA

A cladistic analysis of the Sciuravidae (extinct rodents from North America) and postulated descendant taxa, performed using mainly dental characters, yielded a potential calibration point for molecular clock models. A crown clade, composed of early members of the living superfamilies Muroidea and Dipodoidea (the Myodonta), diverged from Geomyoidea and more basal extinct Myomorpha (including Sciuravidae) during the Eocene. Fossils bracket this split between the Wasatchian-Bridgerian boundary (~50 MA) and the earliest Uintan (~46 MA). The origin of the Myodonta can be compared to another well-documented divergence the Mus-Rattus split at 13.75­11.8 MA (Jacobs and Downs 1994). Two sets of DNA sequence data are sufficiently well-sampled taxonomically and conserved to show this node without ambiguity: exon 10 of the growth hormone receptor (GHR) gene (Adkins et al. ms), and exon 11 of the breast cancer susceptibility (BRCA1) gene (Walton and Adkins, ms.) For both data sets genetic distance per million years is 13­25% greater for the Mus-Rattus split than the nonmyodont-myodont split. The rate of nucleotide substitutions in mice and rats is known to be higher than in other mammal groups (Li et al. 1990); these results suggest rate changes within the lineage of Suborder Myomorpha.

WHAT ARE MASS EXTINCTIONS? A STATISTICAL APPROACH USING DENSITY ESTIMATION

WANG, Steve C., Dept. of Statistics, Harvard University, Cambridge, MA, USA

Do mass extinctions such as the "Big Five" grade continuously into the background extinctions occurring throughout the history of life, or are they a qualitatively distinct phenomenon that cannot be explained by processes responsible for background extinction?

Various criteria have been proposed for addressing this question, including approaches based on physical mechanisms, ecological selectivity, and statistical characterizations. Statistical approaches typically examine quantitative characteristics of mass extinctions (such as metrics of extinction intensity) and compare them to the distribution of such characteristics associated with background extinctions. If mass extinctions are outliers or are separated by a gap from background extinctions, the distinctness of mass extinctions is supported.

In this presentation, we propose a new statistical approach to testing for the continuity of mass extinctions by applying kernel density estimation and bootstrap modality testing. The advantage of this method is that it does not depend on arbitrary choices of parameters (such as bin widths for histograms), and provides a direct estimate of the significance of continuities or gaps in observed extinction intensities. We are thus able to rigorously test whether differences between mass extinctions and background extinctions are statistically significant.

In our method, we assume the existence of an underlying probability density function of extinction intensities from which observed extinctions are sampled. We estimate this density function using kernel density estimation. A unimodal density estimate implies that mass extinctions are the right tail of a continuous spectrum of extinctions; a bimodal density estimate implies that mass extinctions are a distinct phenomenon. We use a bootstrap critical bandwidth test to assess the statistical significance of the observed unimodality or bimodality.

We apply the methodology to Sepkoski's database of Phanerozoic marine families.

THE PRE-LOPINGIAN MARINE BENTHIC CRISIS

WANG, Xiangdong, Shuzhong Shen, and Yugan Jin, Nanjing Institute of Palaeontology and Geology, Chinese Academy of Sciences, Nanjing, China

Marine faunal change prior the Lopingian, which had been viewed as a statistical artifact of a poor fossil record, now appears to be a discrete episode of the End-Permian Extinction. Crinoids, tabulate and rugose corals, bryozaon and fusulinid foraminifera suffered a significant decline near the Guadalupian-Lopingian boundary. Because of the correlation of the extinction level is pending, the duration of this episode and whether it is simultaneous across the globe remain unexamined. Based on the proposed global stratotype for the Guadalupiab-Lopingian boundary in South China and a global of the Lopingian, we made a survey of this biotic change in selected sections in Tethyan, Perigondwana, Arctic, and the continental interior basins of Pangean. The survey shows this crisis was coincident with a major global sea level fall above the Jinogondolella xuanhanensisi Zone of the latest Capitanian, which drained the shallow epi-continental seas of the Gondwana, North America and Boreal Realms. The endemic faunas in these epi-continental seas were extinguished as their habitats were eliminated. However, no significant declination of fossils can be detected across the boundary in the Salt Range. In Tethys, benthic groups that flourished on carbonate platform such as the corals, fusulinids and bryozoans, suffered a significant decline, but the survivors did not produce any new families during the Lopingian. Turnover occurred among brachiopods, ammonoids and conodonts, although diversity remained essentially the same during the Lopingian. Non-fusulinid foraminifera, bivalves and gastropods did not show distinctive changes at the family and generic levels. A depletion of d¹³C carb occurs near the base of the Clarkina dukouensis Zone. To the continental sequences, only the Upper Tatarian is corresponding with the Lopingian Series. Though the boundary closes to the turning point of litho- and biostratigraphic changes, there is no catastrophic event.

UPPER CRETACEOUS AMMONOID TAPHOFACIES IN NORTHWESTERN HOKKAIDO, JAPAN

WANI, Ryoji, Graduate School of Science and Engineering, Waseda University, Tokyo, Japan

Taphonomic attributes of ammonoid shells in the Upper Cretaceous of northwestern Hokkaido, Japan, depend heavily on the nature of the lithofacies. Focused attributes are: fragmentation rate (FR); patterns of ammonoid-size distribution (SD) and mean size (MS); concentration rate (CR); occurrence of heteromorphs (OH); and the number of total individuals (TI). All the results are classified into the following four taphofacies, which were influenced by the differences in the energy levels of sedimentary environments.

Taphofacies 1: Almost all ammonoids are fragmented (FR=96.88%). MS (25.97 mm) and the pattern of SD are almost same as taphofacies 2 and 3A. CR is small (2.46) and OH is high (59.38%). Ammonoids rarely occur (TI=32).

Taphofacies 2: About three-quarters ammonoids are fragmented (FR=76.79%). MS (32.81 mm) and the pattern of SD are almost same as taphofacies 1 and 3A. CR (3.50) is large. OH (64.73%) is the highest within four taphofacies. Ammonoids occur abundantly (TI=224).

Taphofacies 3A: More than 60% of ammonoids are fragmented (FR=64.88%). MS (31.25 mm) and the pattern of SD is almost same as taphofacies 1 and 2. CR (3.80) is the largest within four taphofacies. OH is low (26.83%). Ammonoids occur abundantly (TI=410).

Taphofacies 3B: About half the ammonoids are fragmented (FR=51.65%). MS (64.95 mm) is largest and the pattern of SD is a little different from the others because of abundant occurrences of large ammonoids. CR (2.17) is the smallest and OH is low (27.47%). Ammonoids rarely occur (TI=91).

These taphofacies correspond to such lithofacies as sandstone with some cross-bedding (taphofacies 1), intensively bioturbated sandy siltstone (taphofacies 2), siltstone with frequent intercalations of thick storm sand layers (taphofacies 3A), and siltstone with less frequent intercalations of thin storm sand layers (taphofacies 3B), respectively.

THE USGS NATIONAL PALEONTOLOGICAL DATABASE: PALEODATA

WARDLAW, Bruce R., Nancy R. Stamm, and David R. Soller, U.S. Geological Survey, Reston, VA, USA

The National Paleontological Database (Paleodata) is a component of the USGS Geologic Map Database (http://ncgmp.usgs.gov/ngmdbproject), which has several linked map and support map internet databases. Paleodata is still in the prototype phase of development. The Map Catalog component is 60 percent complete and the Geological Names Lexicon (Geolex) is 80 percent complete.

The Paleodata prototype was developed using Microsoft Access, ArcView, and HTML programs for Manhattan, KS and Guadalupe Peak, TX 1:100,000 scale maps. These quadrangles display the active interplay of stratigraphic information, fossil information, and geologic map information, all tied to a digital topographic map. Information provided includes columnar section, stratigraphic distribution of samples, fossils identified for each sample, and photographs of selected fossils tied to their museum repository numbers. Because the data is so variable, from hand written script of G.H. Girty (1891) to modern fossil distributions and photo-identifications, the quality and detail necessarily varies, but all information is made available. Problems in serving these detailed fossil records include the concerns of several land management agencies about openly accessible locality information. We propose to provide to the public the general paleontologic information, and advise accredited researchers to attain access to sensitive information from local land managers. Upon completion, Paleodata will contain data from authoritative published references, and the Paleontology and Stratigraphy E & R informal reports, a 100+ year legacy of all fossils examined and reported on by USGS paleontologists for geologic mapping projects. The paleontologic data complements the geologic map information available from the Map Catalog and the stratigraphic names reference source available from Geolex. Geolex provides reference summaries to all the geologic unit names and will be directly accessible from the map or stratigraphic section.

DISTRIBUTION OF TRIMERELLID AND PENTAMERID BRACHIOPODS IN SILURIAN REEFS OF SE WISCONSIN AND NE ILLINOIS

WATKINS, Rodney, Milwaukee Public Museum, Milwaukee, WI, USA

Silurian (Wenlockian) reefs of the Racine Formation in SE Wisconsin and NE Illinois show a general increase in size and ecologic complexity over a north-south distance of about 220 km. Around Grafton, in the northern part of this area, reefs reach 60 m in breadth and 3­15 m thick. In the Milwaukee area, reefs reach over 140 m in breadth and up to 20 m thick, and furthest south, the Thornton reef is 2.7 km in breadth and over 90 m thick. Increasing size along the reef trend is accompanied by greater variety of reef lithology, increased abundance of flank beds, and increase in species diversity. Pentamerid brachiopods show an increasing diversity from one to six species southward along the reef tract, paralleling the increase in reef size (Watkins. 1998. Paläontologische Zeitschrift 72:99). Trimerellid brachiopods, which are comparable to pentamerids in medium to large size, lack of attachment, and extensive posterior shell thickness, show an opposite sense of distribution. Highest diversity occurs in the small northern reefs, which contain Rhinobolus davidsoni Hall & Clarke, Dinobolus conradi (Hall), Monomerella greenii Hall & Clarke, and Monomerella prisca Billings. In the Milwaukee area, reefs contain D. conradi, M. prisca, and Trimerella sp., and at Thornton, in the south, Monomerella ovata Whiteaves and M. prisca are present. Both pentamerids and trimerellids shared the same life habit of large, free-lying, posteriorly-weighted sediment recliners, and their reverse trends in distribution may reflect ecologic competition in Racine reefs.

PALEOENVIRONMENT OF SAN FRANCISCO BAY: APPLICATIONS FOR RESTORATION AND MANAGEMENT OF COASTAL WETLANDS

WATSON, Elizabeth B., and Frances Malamud-Roam, Dept. of Geography, University of California, Berkeley, CA, USA

Although San Francisco Bay was formerly ringed with about 190,000 acres of tidal marsh habitat, due to diking, filling, and salt pond construction, there are currently only about 40,000 acres remaining. Areas of moist grassland, vernal pool habitat, mudflats, natural salt pans, and riparian woodland have declined similarly. This loss of wetland has led to increasing interest in the restoration and conservation of remaining wetland resources in the San Francisco Bay/Delta region. While paleoecological studies of such areas are rarely done prior to project planning, the possible contribution of such data is underealized.

In this study, we summarize knowledge of vegetation change in coastal marshes of the San Francisco Bay area throughout the past 3,000 years, gathered through pollen and isotopic proxies. We report on a survey of managers and restoration professionals in order to evaluate the sources of knowledge brought to local and regional restoration projects. Furthermore, we examine case studies outlining the use of paleoecological data in local conservation projects. Through this data, we discuss variations in salinity regimes, knowledge of sedimentation history, future prospects for Bay Area wetlands in regards to sea level rise, and conflicts between environmental history and project goals. Paleoecology can contribute uniquely to an historical study of marshes undertaken as part of comprehensive site assessment, while partnerships between wetland management and research should be strengthened.