R. Timothy Patterson

ERROR-WEIGHTED MAXIMUM LIKELIHOOD (EWML): A NEW STATISTICALLY BASED METHOD TO CLUSTER QUANTITATIVE MICROPALEONTOLOGICAL DATA

ABSTRACr-The advent of readily available computer-based clustering packages has created some controversy in the micropaleontological community concerning the use and interpretation of computer-based biofacies discrimination. This is because dramatically different results can be obtained depending on methodology. The analysis of various clustering techniques reveals that, in most instances, no statistical hypothesis is contained in the clustering model and no basis exists for accepting one biofacies partitioning over another. Furthermore, most techniques do not consider standard error in species abundances and generate results that are not statistically relevant. When many rare species are present, statistically insignificant differences in rare species can accumulate and overshadow the significant differences in the major species, leading to biofacies containing members having little in common. A statistically based error-weighted maximum likelihood (EWML) clustering method is described that determines biofacies by assuming that samples from a common biofacies are normally distributed. Species variability is weighted to be inversely proportional to measurement uncertainty. The method has been applied to samples collected from the Fraser River Delta marsh and shows that five distinct biofacies can be resolved in the data. Similar results were obtained from readily available packages when the data set was preprocessed to reduce the number of degrees of freedom. Based on the sample results from the new algorithm, and on tests using a representative micropaleontological data set, a more conventional iterative processing method is recommended. This method, although not statistical in nature, produces similar results to EWML (not commercially available yet) with readily available analysis packages. Finally, some of the more common clustering techniques are discussed and strategies for their proper utilization are recommended.

Taphonomy of tidal marsh foraminifera: implications of surface sample thickness for high-resolution sea-level studies

Abstract Previous research has shown that intertidal foraminiferal faunas can be used to document Holocene relative sea-level change and large prehistoric earthquakes. Applications like these, however, require an understanding of the impact of infaunal habitat and taphonomic processes on foraminiferal assemblages. To evaluate these effects, we analyzed surface sediment samples collected along a transect across a tidal marsh at Zeballos on Vancouver Island, British Columbia. Samples of the uppermost 10 cm of sediment in the marsh contain foraminiferal assemblages that permit recognition of a greater number of elevation-controlled marsh assemblages than samples of the top centimeter, which are generally used in sea-level studies. This is because the upper 10 cm contain most infaunal foraminifera species, whereas the top centimeter commonly lacks some of these species. A 10-cm thickness is somewhat arbitrary, but most foraminiferal taphonomic biasing occurs in the top 10 cm of the marsh.

OXYGEN LEVEL CONTROL ON FORAMINIFERAL DISTRIBUTION IN EFFINGHAM INLET, VANCOUVER ISLAND, BRITISH COLUMBIA, CANADA

Samples were analyzed from Effingham Inlet, southwestern Vancouver Island, British Columbia, to assess the oceanographic controls on benthic foraminiferal distribution. The resultant proxy data will be used to interpret cores collected throughout the basin, and assess the causes of periodic variation in fish populations over time.nnSeven foraminiferal assemblages were recognized with the primary controlling factors being oxygen content, and proportion of organic matter in the sediment. The estuarine Buliminella Assemblage characterizes well-oxygenated environments with high levels of terrestrial plant matter. This assemblage disappears when oxygen levels fall beneath suboxic levels of 40 μM/kg. The Buccella Assemblage, dominated in part by attached forms and islandiellids, is typical of well-oxygenated bank environments in the region. The Psammosphaera Assemblage is related to the lower salinity and variable conditions present in the shallow water where it occurs. The Stainforthia-Nonionella Assemblage characterizes one well-oxygenated environment outside the inlet. The Stainforthia-Bolivinellina Assemblage is typical of suboxic/dysoxic conditions (10–40 μM/kg) in the outer basin. The Stainforthia Assemblage is identified from dysoxic environments of deepest parts of the outer basin. A gradation between the Stainforthia-Bolivinellina Assemblage and the Stainforthia Assemblage is significant as a whole range of suboxic/dysoxic/anoxic conditions are detectable, potentially permitting recognition of even subtle variations in paleoceanographic/atmospheric circulation. The Stainforthia-Buccella Assemblage was recovered from the least oxygenated area of Effingham Inlet under fully anoxic (with H2S) conditions, and provides evidence that even the most isolated portions of Effingham Inlet are periodically oxygenated.

ASSESSMENT OF ARCELLACEAN (THECAMOEBIAN) ASSEMBLAGES, SPECIES, AND STRAINS AS CONTAMINANT INDICATORS IN JAMES LAKE, NORTHEASTERN ONTARIO, CANADA

Conditions in James Lake vary from uncontaminated and nearly neutral pH conditions through most of the lake, to extremely low pH conditions (2.1 in places) contaminated with Fe, Al and SO4 adjacent to an abandoned pyrite mine near the lake outlet. Six assemblages representative of distinct arcellacean habitats were recognized in sediment-water interface samples collected in the lake using Q-mode Cluster Analysis. R-Mode analysis of this distributional data corroborates previous results indicating that arcellacean strains from within the same species are useful for discriminating environments. Cucurbitella tricuspis dominates most samples and had to be deleted from analysis to determine benthic faunal relationships. This species is seasonally planktic and thus readily transported; it should not be considered in intralake studies. Arcella vulgaris overwhelmingly dominates extremely hostile low pH environments (5.5) near the old mine site in samples where Shannon Diversity Index values of 1.000 are recorded. The highly variable pH in James Lake permitted the determination of precise boundary conditions for distribution of this species. These results indicate that Difflugia protaeiformis ‘‘claviformis’’ is an ideal indicator of industrial contamination under higher pH conditions. The D. protaeiformis ‘‘amphoralis’’ and ‘‘acuminata’’ strains are more closely linked to uncontaminated muddy substrates characterized by high proportions of diatoms, a probable important food source. The presence of Lesquerasia spiralis seems to be partially linked to substrate type with greater numbers typically found in coarser sediments.

Marine saline ponds as sedimentary archives of late Holocene climate and sea-level variation along a carbonate platform margin: Lee Stocking Island, Bahamas

A 1500-year, late Holocene history of coastal and lacustrine carbonate sedimentation is preserved in shallow ponds on Lee Stocking Island, Exuma Cays, Bahamas. Details of environmental change have been extracted by integrating lithostratigraphy, biostratigraphy (macrobiota, foraminifers, ostracodes), and chemical stratigraphy (C, O isotopes of foraminiferal and molluscan skeletal carbonate; MgO wt% of ostracode calcite) with a well defined 14 CA MS radiocarbon chronology. Carbonate deposition began within physically restricted, euryhaline coastal embayments, with several pronounced changes in salinity defined by biotic and calculated salinity variation (from MgO wt% in shells of Cyprideis americana). By about 700‐740 yr B.P., embayment closure occurred possibly related to changed longshore deposition associated with sea level rise and=or regional change in climate (previously documented). With closure, the initial euryhaline foraminifer assemblage was replaced by a predominant hypersaline biofacies (e.g., Triloculina sp.); with progressive basin fill, ostracode assemblages, calculated salinities, and variation in abundance of the gastropod Cerithidea sp. may resolve higher-order (and some extreme) salinity fluctuations throughout the remaining history of saline pond development. Foraminiferal isotope stratigraphy is compatible with that expected for hydrologically closed lake basins. Carbonate accumulation was effectively shut-down<200 years ago, replaced by stromatolitic growth. Present-day salinities vary according to water balance governed by rainfall and evaporation. A centuries-scale (300‐400 year) flux of abraded (reworked), marine-derived bioclasts, admixed with skeletal remains of indigenous biota, is also preserved in these ponds. Allochthonous sediment was transported by hurricane storm surges or related to abrupt transgressive events superimposed on an overall gradual rise in global sea level. We discuss evidence for both as controls on sedimentation. Our study illustrates that saline ponds on Bahamian islands are excellent sedimentary archives of local, regional, and possibly global paleoclimatic events of late Holocene age.

Differential diagenesis of sedimentary components and the implication for strontium isotope analysis of carbonate rocks

Geochemical analyses of various components foraminifera, coccoliths and siliciclastic fractions of limestone and marl . samples from the marine Trubi Formation Early Pliocene of southern Italy revealed subtle diagenetic contamination. The coccolith fraction is altered from its original value both in its trace element Sr rCa, MgrCa, FerCa, MnrCa, NarCa all

PLANKTIC FORAMINIFERAL BIOSTRATIGRAPHY AND 87Sr/86Sr ISOTOPIC STRATIGRAPHY OF THE OLIGOCENE-TO-PLEISTOCENE SEDIMENTARY SEQUENCE IN THE SOUTHEASTERN CALABRIAN MICROPLATE,

Integration of foraminiferal biostratigraphy, 87Sr/86Sr isotope stratigraphy, and traditional physical stratigraphy has provided a refined age control of a poorly known Oligocene-to-Pleistocene sedimentary sequence nonconformably covering the crystalline basement complex of the Calabrian microplate, a continental block which rifted off the southern margin of the European plate during Neogene time. In spite of the fossil-poor content of the sequence, the simultaneous use ofpaleontological and geochemical techniques have resulted in the following conclusions. 1) The age of an unnamed, thin calcarenite unit locally present at the base of the sequence, previously considered Rupelian to early Aquitanian in age, has been refined to Chattian (27.8-24.8 Ma). This calcarenite was considered a basal, conformable member of the overlying Stilo-Capo dOrlando Formation. However, this study indicates that it is separated from the Stilo-Capo dOrlando Formation either by an angular unconformity or by a disconformity representing a significant time interval. 2) The Stilo-Capo dOrlando Formation has a latest Chattian-earliest Aquitanian to Bur- digalian age. Previously published reports suggested deposition over a much longer time span, ranging from late Rupelian to Langhian. 3) An unnamed deep-marine siliciclastic unit mostly composed of conglomerate and sandstone and previously considered Tortonian in age is, in fact, Serravallian to Tortonian. 4) The depositional interval of the trubi, fine-grained marine deposits, has been independently confirmed to span the Pliocene-Pleistocene. The results of this study provide a framework for future sequence-stratigraphic and paleotectonic studies in the area, and prove the effectiveness of an integrated paleontological and geochemical (87Sr/86Sr) approach in the study of fossil-poor sedimentary sequences.

Application of wavelet and regression analysis in assessing temporal and geographic climate variability: Eastern Ontario, Canada as a case study

Abstract Regression and wavelet analysis have been employed to trace and quantify variation in temporal patterns (e.g., cycles and trends) between the instrument climate records of urban Ottawa and nearby rural areas in eastern Ontario. Possible links between observed climate change at these stations and possible natural and anthropogenic drivers were also investigated. Regression analysis indicates that the temperature in Ottawa increased, on average, at a rate of >0.01°C yr−1 in comparison to adjacent rural areas over the last century. Wavelet analysis shows that this relative urban warming trend was primarily manifested in the form of multidecadal and interseasonal cycles that are likely attributable to gradual increased winter heating in Ottawa (heat island effects) associated with population growth. We estimate that the 1°C increase in the Ottawa temperature is equivalent to an increase in population size of ∼400,000. In contrast, interannual variability correlates well between rural and urban areas with about the same temperature amplitudes.

NON-MARINE OCCURRENCE OF THE FORAMINIFER CRIBROELPHIDIUM GUNTERI IN NORTHERN LAKE WINNIPEGOSIS, MANITOBA, CANADA

Analysis of sediment samples from the sediment-water interface of Point River Bay, northern Lake Winnipegosis, a very large lake in central Manitoba, indicates that Cribroelphidium gunteri, a coastal marine foraminifer, is living and has adapted to this northern lake environment in salinities as low as 1–2‰. In Point River Bay, summer water temperatures reach 15.6°C, marginally above the minimum 14.5°C required for reproduction by C. gunteri. This benthic foraminifer colonized saline parts of the lake during the warm Holocene Hypsithermal (6000–3500 years BP), probably by avian transport. Previous analysis of stratigraphic data suggested that C. gunteri had died out in this area as conditions became cooler. This hypothesis had been corroborated by the post-Hypsithermal retreat of the marine range of C. gunteri from the Maritimes of Atlantic Canada to the south of Cape Cod, MA. Although recent colonization of the lake cannot be precluded, marine source populations of C. gunteri are now quite distant, making the only viable colonization mode, avian transport, very difficult. The adaptation of the mid-Holocene populations of this species to the progressively colder post Hypsithermal climate and often to extremely low salinity values in Lake Winnipegosis is remarkable. The great abundance of C. gunteri in sediments of Lake Winnipegosis, in some areas making up most of the sediment, also raises potential concerns about the interpretation of supposed marine sections based exclusively on the presence of foraminifera.

An illustrated key to the identification of unilocular genera of calcareous foraminifera

ABSTRAcr-Taxonomic keys are rarely used as an aid to the identification of foraminifera. Such keys become increasingly attractive, however, as the number of taxa which must be distinguished becomes large. The proliferation of known genera over the last 25 years is nowhere more apparent than in the unilocular calcareous foraminifera, where the number of genera has risen from 5 to 46. We present herein a dichotomous key in which any species may be assigned to its proper genus by progressing through a series of steps, consisting of paired statements, in which only one choice is made at a time.