Patterson Lab Publications 1999-2001

Patterson, R.T., Wright, C., Chang, A.S., Taylor, L.A., Lyons, P.D., Dallimore, A., and Kumar, A. 2001. Atlas of common squamatological (fish scale) material in coastal British Columbia, and an assessment of the utility of various scale types in paleofisheries reconstruction. Palaeontologia Electronica 4 (2): 88 pp.

Squamatological (fish scale) material from 48 common species found in coastal waters of British Columbia is presented. Fish-scale remains of extant species are well-preserved in Holocene core sediments in various anoxic basins along the coast of British Columbia. These remains are of considerable value in assessing natural variation in fish populations over time. Comparative micrographs of modern fish scales as well as an assessment of their preservation potential is provided. Photographs of various scales preserved in the sedimentary record (e.g., herring, rockfish, sardines, surfperch) are provided and discussed in the context of the taphonomic alteration that typically occurs after burial. This monograph, the first atlas of fish-scale material available for the northeast Pacific will help resolve identification problems for future fish taxonomists, paleoceanographers, and fisheries-oriented researchers.

Prokoph, A., Fowler, A.D., and Patterson, R.T. 2001. Periodically forced self-organization in the long term evolution of planktic foraminifera. Canadian Journal of Earth Science 38 (2): 293-308. https://doi.org/10.1139/e00-037

Wavelet transform and other signal analysis techniques suggest that the planktic foraminiferal (PF) long-term evolutionary record of the last 127 Ma can be attributed to complex periodic and nonlinear patterns. Correlation of the PF extinction pattern with other geological series favors an origin of the ~30 Ma periodicity and self-organization by quasi-periodic mantle-plume cycles that in turn drive episodic volcanism, CO2-degassing, oceanic anoxic conditions, and sea-level fluctuations. Stationary ~30 Ma periodicity and a weak secular trend of ~100 Ma period are evident in the PF record, even without consideration of the mass extinction at the K-T boundary. The 27-32 Ma periodicity in the impact crater record and lows in the global sea-level curve, respectively, are ~6.5 Ma and ~2.3 Ma out of phase with PF-extinction data, although major PF-extinction events correspond to the bolide impacts at the K-T boundary and in late Eocene. Another six extinction events correspond to abrupt global sea-level falls between the late Albian and early Oligocene. Self-organization in the PF record is characterized by increased radiation rates after major extinction events and a steady number of baseline species. Our computer model of long-term PF evolution replicates this SO pattern. The model consists of output from the logistic map, which is forced at 30 Ma and 100 Ma frequencies. The model has significant correlations with the relative PF-extinction data. In particular, it replicates singularities, such as the K-T event, nonstationary 2.5-10 Ma periodicities, and phase shifts in the ~30 Ma periodicity of the PF record.

Boudreau, R.E.A., Patterson, R.T., McKillop, W.B., and Dalby, A.D. 2001. Non-Marine occurrence of the foraminifer Cribroelphidium gunteri in Lake Winnipegosis, Manitoba.Journal of Foraminiferal Research 32 (2):108-119. https://doi.org/10.2113/0310108

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 Hypsitherml (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 has 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 population of this species to the progressively colder post Hypsithermal climate and often to extremely low salinity values in Lake Winniegosis is remarkable. The great bundance 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.

Guilbault, J.-P., Patterson, R.T. 2001. Correlation between marsh foraminiferal distribution and elevation in coastal British Columbia, Canada, Proceedings of the Fifth International Workshop on Agglutinated Foraminifera” edited by Malcolm Hart, Michael Kaminski, Chris Smart, p. 117-125. ISBN 83-901164-9-9. 479pp

Distribution of marsh foraminifera at two sites 120 km apart on the west coast of Vancouver Island, British Columbia show a marked linear correlation with elevation. In particular, strong correlations are shown by Miliammina fusca (-0.94) and by the grouping of Balticammina pseudomacrescens, Jadammina macrescens and Trochamminita salsa (0.92). Highest correlation values are found in samples that include at least the top 2 to 3 cm–and particularly up to 10 cm–of surface sediment. Foraminifera from samples limited to the top centimeter correlate less well as the effect of infaunal habitat, taphonomic effects, and short term environmental variations have not been smoothed out.

Reinhardt, E.G., Cavazza, W., Patterson, R.T., and Blenkinsop, J. 2000. Differential diagenesis of sedimentary components and the implications for strontium isotope analysis of carbonate rocks. Chemical Geology 164 (3,4): 331-343. https://doi.org/10.1016/S0009-2541(99)00147-3

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/Ca, Mg/Ca, Fe/Ca, Mn/Ca, Na/Ca all were higher) and isotopic ( ⁸⁷Sr/ ⁸⁶Sr, δ¹⁸O, δ¹³C) composition. Coccolith ⁸⁷Sr/ ⁸⁶Srvalues (limestones 0.709010; marls 0.708951) are lower than those of coeval Early Pliocene seawater (0.709025–60 [Farrell, J.W., Clemens, S.C., Gromet, L.P., 1995. Improved chronostratigraphic reference curve of Late Neogene seawater ⁸⁷Sr/ ⁸⁶Sr. Geology 23, 403–406]) and similar to the ⁸⁷Sr/ ⁸⁶Srvalues of Messinian evaporites (0.70887 to 0.70896 [Müller, D.W., Mueller, P.A., 1991. Origin and age of the Mediterranean Messinian evaporites: implications from Sr isotopes. Earth Planet. Sci. Lett. 107, 1-12]). Foraminiferal calcite is unaltered and retains its elemental and isotopic composition, with ⁸⁷Sr/ ⁸⁶Srvalues (0.709052) within the range for Early Pliocene seawater. However, unaltered ⁸⁷Sr/ ⁸⁶Srvalues were obtained only when the foraminifera were cleaned in acid to remove all contaminating coccoliths. Simple hand-picking and ultrasonic cleaning in water is inadequate to remove adhering coccoliths and may result in erroneous ⁸⁷Sr/ ⁸⁶Srvalues being quoted.

Keyword(s): Foraminifera; Sr isotopes; Trace elements; Stable isotopes; Diagenesis

Lyons, P.D, Patterson, R.T., and Rioux, M., 2000. Application of a Three-Dimensional Color Laser Scanner to Paleontology: An Interactive Model of a Juvenile Tylosaurus sp. Basisphenoid-Basioccipital. Palaeontologia Electronica, 3.2: 16 p.

Three-dimensional (3D) modeling has always been an important part of paleontological research and interpretation though digital reproductions of fossils are a recent phenomena. A highly accurate, interactive, 100 micron resolution, 3D, digital model of a fossilized basisphenoid-basioccipital from a juvenile Tylosaurus sp. mosasaur was generated using a 3D laser scanner and manipulated using VRML and InnovMetric polygon files. This 3D model supports varying levels of magnification depending on the initial scan resolution and the amount of post-production polygon reduction. The generation of these 3D models is relatively simple because the software and technology for their generation is relatively mature. At present, complex 3D models require powerful computers in order to manipulate their computer graphic substructures. But, as computer technology improves, digital 3D scanning could prove invaluable for creating and sharing virtual copies of fossil material. Primary results of this study indicate that for most paleontological applications a 100 micron scan resolution is acceptable.

Kumar, A., and Patterson, R.T. 2000 Arcellaceans (Thecamoebians): new tools for monitoring long and short term changes in lake bottom acidity. Environmental Geology 39 (6):  689-697. https://doi.org/10.1007/s002540050

James Lake, northeastern Ontario, Canada, has been impacted by the dumping of waste rock from a pyrite mine. High levels of Fe, Al and SO₄ and low pH (2.0-5.5) are recorded in the lake. The configuration of the lake and current direction result in contaminated areas being restricted to the southwestern portion of the lake. Near neutral pH and low metal levels are recorded elsewhere. Analysis of arcellacean faunas from the lake indicate that one species, Arcella vulgaris, is able to thrive in even the most hostile areas of the lake. The absence of other arcellaceans indicative of contaminated substrates in higher pH lakes, such as centropyxids and Difflugia protaeiformis strains, suggests that pH is the dominant control over this assemblage. Analysis of arcellaceans from a core at the site indicates that contamination and acidification (pH values < 5.5) problems in James Lake have existed for at least 1300 years, clearly predating mining activity. Prior to that time high proportions of centropyxid species indicate less acid conditions (pH >5.5) prevailed, but a stressed environment existed for several thousand years. The recognition that Arcellacean faunas can now be used to characterize both low and high pH industrially, and naturally contaminated environments, provides an important new paleolimnological tool.

Dalby, A.P., Kumar, A., Moore, J.M. and Patterson, R.T. 2000. Utility of arcellaceans (thecamoebians) as paleolimnological indicators in tropical settings: Lake Sentani, Irian Jaya, Indonesia. Journal of Foraminiferal Research 30 (2): 135-142. https://doi.org/10.2113/0300135

Arcellacean (thecamoebian) assemblages recovered from Lake Sentani, a large tropical lake southwest of Jayapura, Irian Jaya, Indonesia, are characterized by low diversity and low abundances. Dominated by Centropyxis aculeata and Arcella vulgaris, this fauna is similar to those indicative of stressed environments (brackish conditions, high levels of industrial contaminants) in temperate regions. However, neither condition exists in Lake Sentani. Previous work has determined that the lake is oligomictic, characterized by weak circulation with turnover occurring every few years. Prolonged isolation of the lake bottom produces progressively reduced oxygen levels and results in reduced productivity amongst benthic organisms. The feeble stratification that exists here creates reduced oxygen levels at depth providing a likely explanation of the stressed arcellacean fauna. The oligomictic conditions observed here and the resultant fauna are widespread and are characteristic of a large proportion of tropical lakes around the world. As the low bottom water oxygen conditions will have a serious impact on most benthic organisms in these lakes, other limnological signals including anthropogenic contamination will be masked. This is a disappointing result as the utility that had been developed for the group as a limnological indicator in temperate lakes does not appear to apply in a significant proportion of low latitude lakes.

Prokoph, A., Fowler. A.D., Patterson, R.T. 2000. Evidence for periodicity and nonlinearity in a high-resolution fossil record of long-term evolution. Geology 28 (10): 867-870. doi:10.1130/0091-7613(2000)28<867:EFPANI>2.0.CO;2

The application of new signal analysis techniques provides increased insight into the study of the fossil record and processes of evolution. The fossil record of 622 planktic foraminifera contains data from 200 stratigraphic stages of the past 127 m.y. Time-series analyses (wavelet and Fourier transform) of the planktic foraminifera fossil record were used to discern periodic components in long-term evolution. The correlation function analysis was used to distinguish between random and deterministic behavior of the fossil record. The analyses show that stationary approximately 30 m.y. periodicity and complex deterministic patterns occur in the long-term planktic foraminifera evolution, in particular in the extinction record. Our results suggest that the occurrence of intense diversity fluctuations with 3-10 m.y. periodicity after major extinction events may be attributed to nonlinear, self-organized evolutionary response to the availability of new ecospace. This coupled nonlinear-periodic scenario may explain the repetitive appearance of similar morphotypes in approximately 30 m.y. intervals.

Patterson, R.T. 2000. The Secret to a Long Life. Editorial Commentary. Palaeontologia Electronica, 3.2: 4 p.

With the release of this issue, Palaeontologia Electronica (PE) will have completed three years of publication. Paleontologia Electronica has come a long way since its first conception as a series of discussion threads on PaleoNet in 1995 and later brain-storming on the Electronic Paleontological Journal listserver in 1995-1997. With the completion of this volume, two founding members of PE will be stepping down. Bill Riedel, after a long and successful career at Scripps Institution of Oceanography in La Jolla, California is retiring to the vineyards of his native Barossa Valley in South Australia. On behalf of the entire PE publication team, I would like to thank Bill for his untiring service. I am the other “retiree”. Although I am not ready to hang up my professional hat yet, with PE hitting its stride it is time for me to pursue other endeavors. As Michelle Shocked noted in her 1986 “Texas Campfire tapes”, the “Secret to a Long Life (is knowing when it’s time to go)”. I would like to thank all of those in the PEfamily for making my term as one of the two Executive Editors a great experience. In particular, I would like to thank our Technical Editor Jennifer Rumford. Despite sharing several e-mails a day and phone calls too numerous to count, Jennifer and I have never met in person, a testament to the power and utility of the Internet as a publishing environment.

Full text of commentary available at the pdf link above.

Patterson, R.T., Kumar, A. 2000 Use of arcellacea to gauge levels of pollution and remediation of industrially polluted lakes, in Martin, R.E. (ed) Environmental Micropaleontology, vol. 15 of Topics in Geobiology, Kluwer Academic/Plenum Publication, p. 257-278.  https://doi.org/10.1007/978-1-4615-4167-7.

Arcellaceans are microscopic testate rhizopods found in a large number of freshwater and brackish environments. Their agglutinated shells, cemented in an organic matrix, are almost impervious to dissolution. Arcellaceans are ideal for statistical analysis because they are very abundant in Recent and late Quaternary sediments (several hundred per cc). Recent research in lakes contaminated by mine tailings in northeastern Ontario, Canada has indicated that they are sensitive indicators of a number of anthropogenic environmental factors including pH and heavy metal contamination. In particular, their asexual reproductive mode results in the production of environmentally influenced “strains” that are particularly useful in identifying distinctive chemically polluted and remediated benthic environments in lakes. Arcellaceans have a simple morphology, making them easy to identify. They occur in materials that are simple to prepare for examination, making them cost effective indicators of both long and short-term environmental change in lacustrine environments.

Patterson, R.T., Guibault, J.-P., and Thomson, R.E. 2000. Oxygen Level Control on Foraminiferal Assemblage Distribution in Effingham Inlet, Vancouver Island, British Columbia. Journal of Foraminiferal Research 30: 321-335. doi:10.2113/0300321

Samples were analyzed from 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.

Seven 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; it provides evidence that even the most isolated portions of Effingham Inlet are periodically oxygenated.

Patterson, R.T., Kumar, A., 2000. Assessment of arcellacea (thecamoebian) assemblages, species and strains as contaminant indicators in variably contaminated James Lake, north Eastern Ontario. Journal of Foraminiferal Research 30: 310-320. doi:10.2113/0300310

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 cluster 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 vulgarisoverwhelmingly 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 Difflugia protaeifronis “amphoralis” and “acuminatea” strains are more closely linked to uncontaminated muddy substrates characterized by high proportions of diatoms, a probably important food source. The presence of Lesquerasia spiralis seems to be partially linked to substrate type with greater numbers typically found in coarser sediments.

Patterson, R.T., Guibault, J.-P., Hutchinson, I., Clague, J.J. 2000. A comparison of the vertical zonation of diatom, foraminifera, and macrophyte assemblages in a coastal marsh: implications for greater paleo-sea level resoluton. Micropaleontology 46 (3): 299-244. doi:10.2113/46.3.229

Researchers generally use only one type of plant or animal to study a particular marsh. Consequently, it has been impossible to directly compare zonations obtained using different groups between sites. To facilitate such comparison, cluster analysis of foraminiferal, diatom, and macrophyte data collected in transects from a tidal marsh at Zeballos, northwestern Vancouver Island, British Columbia, was carried out. These analyses yielded three, six, and four mostly elevation-controlled assemblage zones, respectively. Physical parameters such as salinity and oxygen concentration affect the various taxa differently, resulting in significantly different assemblage boundaries between groups. A composite analysis of all groups yielded an assemblage zonation very similar to that obtained with the macrophytes alone. Although fewer assemblage zones were resolved with the composite analysis than with the diatom data alone, fewer sample misclassifications resulted in more precise elevation determinations. A second composite analysis using only foraminiferal and diatom data, which is more useful to paleo-sea level researchers, also gave four elevation controlled assemblage zones, although assemblage zone elevational boundaries differed slightly from those obtained with data from all groups. Our results will permit researchers working on diatoms, foraminifera or macrophytes to calibrate their zonations thus making it easier for workers in different fields to compare their results.

Martin, R.E., Goldstein, S.T., and Patterson, R.T. 1999. Taphonomy as an environmental science. Palaeogeography, Palaeoclimatology, Palaeoecology, 149:vii-viii. https://doi.org/10.1016/s0031-0182(98)00187-4

Geology is the study of the history of the Earth and its Life. Paleontology, of course, is no different, and neither is taphonomy: taphonomists regularly infer taphonomic pathways and histories of biogenic particles. Taphonomy, paleontology, and geology are, then, historical sciences.

Geology, paleontology, and taphonomy are also ‘environmental’ sciences because their practitioners study ancient settings and their modern analogs. But unlike, say, physicists, chemists, or most ecologists, who often employ a reductionist approach over very short time scales (geologically speaking), Earth scientists deal with processes that typically occur over time scales much longer than those observable over one or a few human generations. The rates of these processes may be so imperceptible that the environment appears constant to us, when in fact it is changing. It is this perspective on time that is arguably the most valuable contribution that the Earth sciences have made to mankind’s view of itself and its surroundings, and makes paleontology so eminently suitable to confront the environmental problems that now face society (Frodeman, 1995; Martin, 1998, 1999).

Full text of preface available at the pdf link above.

Clague, J.J., Hutchinson, I., Mathewes, R.W., and Patterson, R.T. 1999. Evidence for late Holocene tsunamis at Catala Lake, British Columbia. Journal of Coastal Research, 15 (1):45-60. https://www.jstor.org/stable/4298914

Thin sheets of sand and gravel occur within a sequence of fine organic-rich sediments at Catala Lake, off the west coast of Vancouver Island, British Columbia. The uppermost of these coarse sheets thins and fines landward away from the lake outlet, consistent with deposition by a tsunami. This coarse sediment sheet has been radiocarbon dated to some time after AD 1655; we suggest that it was deposited in 1700 by the tsunami of the last great earthquake at the Cascadia subduction zone. Abundant plant macrofossils, derived from nearby forest, are present within and on top of the sand and gravel layer, suggesting that the tsunami transported forest-floor litter, mosses, and seeds into Catala Lake. Deposition coincided with abrupt changes in diatom and foraminifera communities in the lake. The post-tsunami diatom assemblage is more marine in character than the immediate pre-tsunami assemblage, and the foraminifera community became more diverse after the tsunami. These changes are due either to coseismic subsidence or erosion of the outlet by the tsunami, which increased tidal exchange between the sea and the lagoon that was the precursor to Catala Lake. Older coarse sediment layers in cores from Catala Lake and the bordering marsh may also be tsunami deposits. One of these layers is about 1,000 years old and dates to the time of the penultimate great Cascadia earthquake.

Dix, G.R., Patterson, R.T., and Park, L.E. 1999. Marine saline ponds as sedimentary archives of sea level and climate variation in the Late Holocene: an example along a carbonate platform margin, Bahamas. Palaeogeography, Palaeoclimatology, Palaeoecology, 150:223-246.

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 ¹⁴C AMS 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 percent 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.

Patterson, R.T., Guibault, J.-P., Clague, J.J. 1999. Taphonomy of tidal marsh foraminifera: implications of surface sample thickness for high-resolution sea-level studies. Palaeogeography, Palaeoclimatology, Palaeoecology, 149:199-211

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.