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The Subglacial Antarctic Lakes Scientific Access (SALSA) Project accessed Mercer Subglacial Lake using environmentally clean hot-water drilling to examine interactions among ice, water, sediment, rock, microbes and carbon reservoirs within the lake water column and underlying sediments. A ~0.4 m diameter borehole was melted through 1087 m of ice and maintained over ~10 days, allowing observation of ice properties and collection of water and sediment with various tools. Over this period, SALSA collected: 60 L of lake water and 10 L of deep borehole water; microbes >0.2 μm in diameter from in situ filtration of ~100 L of lake water; 10 multicores 0.32–0.49 m long; 1.0 and 1.76 m long gravity cores; three conductivity–temperature–depth profiles of borehole and lake water; five discrete depth current meter measurements in the lake and images of ice, the lake water–ice interface and lake sediments. Temperature and conductivity data showed the hydrodynamic character of water mixing between the borehole and lake after entry. Models simulating melting of the ~6 m thick basal accreted ice layer imply that debris fall-out through the ~15 m water column to the lake sediments from borehole melting had little effect on the stratigraphy of surficial sediment cores.
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.
An interval of the Early to Middle Pleistocene history of the California Borderland was assessed using multivariate analysis of foraminifera from the Santa Barbara Formation at Bathhouse Beach, Santa Barbara, California. A census of 93 species of benthic foraminifera and nine species of planktonic foraminifera was compiled from 11 samples from the shelly marls, silts, and sands of the lower member. Most species of benthic foraminifera are rare and only 38 species comprise one percent or more of the population in one or more samples.
Paleoenvironment of the sea floor was determined based on benthic foraminifera. R-mode cluster analysis defined five associations which are similar to those of the present-day banks and terraces of the California Borderland. Q-mode cluster analysis grouped samples into four biofacies which characterize shallow banks near 50 meters water depth and off-shore ridges and deep banks averaging 150 meters water depth. The stratigraphic succession of biofacies indicates two transgressive cycles separated by an apparent disconformity between 7.5 and 8.9 meters above the base of the section (between samples 3 and 4).
Paleoceanography of surficial waters was interpreted from planktonic foraminifera. Paleotemperature was assessed from the proportion of sinistral to dextral morphs and from the proportion of encrusted, compact morphs to reticulate, globular morphs of Neogloboquadrina pachyderma. The coiling morphs show a warm interval from the base of the section to about 12 meters (between samples 5 and 6), and a cooler interval from about 12 meters to about 24 meters (between samples 10 and 11), and an interval of intermediate paleotemperature in the topmost sample of the section. Changes in the planktonic assemblage do not coincide with the transgressive cycles inferred from the benthic biofacies.
The Bathhouse Beach section can be placed chronostratigraphically based on planktonic foraminiferal coiling shifts and strontium isotopic data. The isotopic age range of 400 to 900 Kyr brackets the 600 Kyr age assigned by Lagoe and Thompson (1988) to the Neogloboquadrina pachyderma coiling dominance interval CD9/CD8 boundary which occurs midway in the section, between samples 5 and 6.
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.
Currently some controversy exists in the micropaleontological community concerning the statistically correct number of counts required for quantitative examinations, particularly with respect to the effect of variations in the number of species between samples and the significance of varying fractional abundances on the reliability of results. This analysis of the various statistical methods used to determine the number of required counts has shown that the number of species has no relationship to the number of counts required to measure accurately fractional abundances. As part of the study, logarithmic contours plotting percentage abundance against the total number of specimens, which provide abundance errors at a 95 percent confidence level, have been generated. The plot is displayed logarithmically to emphasize the significance of rare microfossil elements that dominate most assemblages, and which are important in many paleoenvironmental studies. Based on the plot, it is recommended that researchers utilize counts of at least 50 for indicator species having a fractional abundance of approximately 50 percent or greater; 300 counts for species which comprise approximately 10 percent of a sample; 500–1,000 counts for species that make up 5 percent of a sample; and counts of several thousand for defining species that comprise 1 percent of a sample. It is important to note, however, that where similar biofacies are involved, higher counts are required to accurately distinguish them. It is also recommended that researchers include fractional error abundances with their estimated abundances to provide an indication of their accuracy.
A benthic foraminiferal fauna of 39 species was quantitatively examined from a late Pleistocene marine terrace deposit near Goleta, California. This foraminiferal fauna, dominated by Cribroelphidium microgranulosum, Buccella tenerrima, Buliminella elegantissima, and Cribroelphidium tumidum, is presently most common in cool, shallow (<12 m, but usually 0–5 m) subtidal environments north of Point Conception, California. This indicates slightly cooler water temperatures during the time of deposition than found near Goleta today, and agrees closely with the results of a previous paleoenvironmental interpretation of the section based on molluscan fossils.
Thirty-two new species of unilocular benthic foraminifera were described from 50 Late Oligocene to Pleistocene samples from DSDP Site 357 (Leg 39) on the Rio Grande Rise in the southwest Atlantic Ocean. These new species make up nearly one-third of the 112 species of unilocular foraminifers identified in the core. Such a high proportion of new taxa is not unexpected as the group has been ignored by most researchers.
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 of paleontological 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 d'Orlando Formation. However, this study indicates that it is separated from the Stilo-Capo d'Orlando Formation either by an angular unconformity or by a disconformity representing a significant time interval. 2) The Stilo-Capo d'Orlando Formation has a latest Chattian–earliest Aquitanian to Burdigalian 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.
Ten new species of benthic foraminifera are described from the early to middle Pleistocene Bathhouse Beach locality of the Santa Barbara Formation, Santa Barbara, California. The new taxa include Glabratella luxuribulla n. sp., Rectobolivina ruida n. sp., Homalohedra jungocostata n. sp., Homalohedra quasilineata n. sp., Pytine lemniscata n. sp., Lagena complurecosta n. sp., Lagena compressacosta n. sp., Cerebrina adamanta n. sp., Fissurina artolabiata n. sp., and Fissurina infragilella n. sp. Palliolatella immemora is proposed as a replacement name for the primary homonym Lagena neglecta Buchner, 1940.
Annectina viriosa, a new species of Ammodiscidae (Foraminiferida), is described from Recent brackish ponds on a salt flat adjacent to Lake Winnipegosis, Manitoba. Colonization of the ponds was probably by avian transport. The distinct morphotype is either the result of an allopatric speciation event within the last 5,000 years or it is a previously undescribed species of shallow-water Annectina from nearby Hudson Bay. It is also possible that recovered specimens are previously unrecognized ecophenotypic variants of some known species produced by unknown hostile environmental factors within the pond ecosystem. The latter hypothesis is difficult to test without extensive biological culturing. The large number of phenotypically stable specimens living in these ponds warrants recognition of these populations as a distinct taxon.
A healthy gut microbiota plays many crucial functions in the host, being involved in the correct development and functioning of the immune system, assisting in the digestion of certain foods and in the production of health-beneficial bioactive metabolites or ‘pharmabiotics’. These include bioactive lipids (including SCFA and conjugated linoleic acid) antimicrobials and exopolysaccharides in addition to nutrients, including vitamins B and K. Alterations in the composition of the gut microbiota and reductions in microbial diversity are highlighted in many disease states, possibly rendering the host susceptible to infection and consequently negatively affecting innate immune function. Evidence is also emerging of microbially produced molecules with neuroactive functions that can have influences across the brain–gut axis. For example, γ-aminobutyric acid, serotonin, catecholamines and acetylcholine may modulate neural signalling within the enteric nervous system, when released in the intestinal lumen and consequently signal brain function and behaviour. Dietary supplementation with probiotics and prebiotics are the most widely used dietary adjuncts to modulate the gut microbiota. Furthermore, evidence is emerging of the interactions between administered microbes and dietary substrates, leading to the production of pharmabiotics, which may directly or indirectly positively influence human health.