A geyser mound, which has formed around the vent of an abandoned well-bore in the Tokaanu geothermal area (North Island, New Zealand) over the last 50 years, is formed primarily of white opal-A along with lesser amounts of black opal-A, reticulate, amorphous or poorly crystalline clay, halite, and scattered detrital quartz grains. Despite the boiling water ejected from the vent, at least 19 taxa of silicified microbes are present in the geyserite. Calothrix, Phormidium, and Synechococcus dominate. Other microbes, including local concentrations of diatoms, are widely scattered. The dominance of cyanobacteria is enigmatic given that these microbes typically are found in cooler water environments (< 60°C) on the medial to distal parts of geyser and hot-spring discharge aprons.

The proximal zone around a geyser vent is environmentally unstable because it oscillates between periodic eruptions of boiling water and cooler phases in accord with the eruptive cycle of the geyser. Thus, the environmental niches on a geyser mound are temporally and spatially variable. The periodicity, duration, and magnitude of the eruptions, and the dispersal patterns of boiling water during eruptions control the distribution of the microenvironmental niches and their temporal changes. Dispersal and cooling of the ejected water will, for example, be controlled by factors such as height of the erupted water, ambient air temperature, and prevailing wind direction.

Biotas compatible with relatively cool waters may thrive on geyser mounds because they inhabit areas that are not inundated constantly by boiling water. Their development and the sinter fabrics that they generate in the proximal zone of a geyser vent means that ancient deposits must be interpreted with caution.

Bivalve mollusks are biological chart recorders: their shells contain a record of environmental conditions in the form of geochemical variation. However, these records are often incomplete. Growth cessations and/or changing growth rates can reduce the range and resolution of the recorded environmental conditions.

To investigate the effects of these variables on geochemical profiles, stable oxygen isotope (δ¹⁸O) profiles were modeled using several growth parameters. Two sets of profiles were calculated: one with constant daily increment widths, the other based on the annual pattern of daily increment width variation observed in the northern Gulf of California bivalve mollusk Chione cortezi. In both sets of models, multi-year δ¹⁸O profiles were calculated assuming that the bivalve shell grows continuously throughout its life. Other profiles were calculated to simulate an ontogenetic decrease in growth rate by decreasing the growth period, daily growth rate, or both. Altering the growth period simulates the effects of thermal thresholds, above or below which no shell material is deposited. Decreasing the daily growth rate results in lower annual shell growth rates while keeping the growth period constant. Combining the two provides a more accurate representation of bivalve shell growth in many subtropical and temperate species.

In addition to the modeling exercise, the shell of a Chione cortezi that lived in the northern Gulf of California was sampled in two ways. First, low-resolution (300 micron) samples were recovered from the entire growth profile along the axis of maximum shell height (umbo to the commissure). Second, high-resolution (50 micron) samples were taken from regions of the shell representing winter growth from late in the bivalve's life.

Modeling results and observations indicate that the fullest range of environmental conditions only is reflected in the earliest years of growth; profiles from successive years have reduced amplitudes, sample resolutions, or both. Variation of intra-annual growth rate in models simulating continuous growth can produce cuspate δ¹⁸O profiles that mimic shutdowns. More detailed sampling in later stages of ontogeny can reconstruct a fuller range of environmental conditions. Finally, within-shell trends in isotopic amplitudes and averages may reflect decreases in growth rate rather than environmental fluctuations. Therefore, particular care should be taken when interpreting inter-annual isotope profiles from long-lived species.

Examination of ontogenetic variation in the stable isotopic composition of accretionary biogenic hard parts is becoming a commonplace technique for gaining insights into organism age, changes in growth rate through ontogeny, and environmental conditions under which organisms lived. However, the application of isotopic data to life-history studies often is impeded by the noisy nature of environmental signals, as well as by seasonal cessation of hardpart accretion. A computational approach is presented that quantitatively resolves secular (seasonal) change in environmental parameters such as temperature and salinity with spatial (hard part) variation in isotopic composition. Output consists of determinations of mean annual isotopic composition, seasonal range in isotopic composition, and variation in hard-part growth rate for any interval of data in an accretionary transect. Quantitative estimates of absolute growth rates, as well as the proportion of each season represented by hard-part accretion, are derived for every season of the organism's life recorded in their hard parts.

This methodology is applied to δ¹⁸O data from a valve of the surf clam, Spisula solidissima, collected live from the New Jersey shelf. Based on the saw-toothed pattern of δ¹⁸O variation in this clam, and on the fact that observed amplitudes of δ¹⁸O variation are only a fraction of those anticipated from measurements of ambient water salinity and temperature, it is apparent that growth cessation occurred during each of the dozen summers and dozen winters of ontogeny. Determination of best-fit sinusoids for each season of growth reveals that: (1) rate of growth decreased exponentially during the ontogeny of this individual; (2) net spring season accretion was initially twice that in the fall; and (3) ontogenetic decrease in net accretion was accomplished in part by reduction in rate of accretion, and in part by reduction in the number of spring and fall days during which growth occurred. Isotope thermometry suggests that all growth intervals span an optimum temperature; shorter (or longer) durations of seasonal shell accretion occur over narrower (or wider) temperature ranges centered on about 11°C.

Beyond the obvious paleoenvironmental applications, the advantage of this method for biologists and paleontologists is that rate and duration of growth can be approximated at seasonal to subseasonal levels of resolution for any living or fossil organism. Such information from a suite of individuals can reveal how growth within a species is affected by changes in latitude, depth, productivity, anthropogenic influence, and other environmental gradients. In addition, because changes in rate and timing of growth within a lineage are the mainstay of heterochrony studies, quantitative methods for assessing such variables through time in fossil specimens will allow more rigorous testing of evolutionary hypotheses.

Permian-Triassic boundary (PTB) sections from isolated carbonate platforms in the Nanpanjiang Basin of south China contain Upper Permian skeletal packstones with diverse open-marine fossils overlain by a 7–15 m thick boundary horizon composed of calcimicrobial framestone constructed by globular to tufted, calcified cyanobacteria similar to Renalcis. The framestone contains interbeds of lime-grainstone with abundant thin-shelled bivalves and brachiopods. The overlying Lower Triassic strata contain microgastropod lime-packstones followed by a thick succession of thin-bedded lime-mudstones.

The PTB event horizon is interpreted to occur at the top of the packstone containing diverse, open-marine fauna and Palaeofusulina and coincident with the abrupt change to calcimicrobial framestone lacking Permian macrofossils. The conformable biostratigraphic boundary occurs at the first appearance of Hindeodus parvus within the basal meter of the calcimicrobial framestone.

Intensively studied PTB sections in south China, such as the GSSP at Meishan, primarily are condensed sections from deep-water, basin environments that contain a thin (< 30 cm) boundary horizon of claystone and lime-mudstone or marl. The sections reported herein are fundamentally different in that they consist of shallow-marine carbonate facies, contain a thick boundary horizon composed of calcimicrobial framestone, and lack evidence of an abrupt shift in depositional environment or water depth. The calcimicrobial framestone boundary horizon occurs in all of the isolated carbonate platforms in the Nanpanjiang Basin. A similar microbial facies has been found in the basal Triassic H. parvus zone in the Sichuan Basin and in Japan. Distribution of the calcimicrobial framestone suggests that it may represent an anomalous oceanic event that affected a vast area of the equatorial eastern Tethys and Panthalassa during and/or immediately following the end-Permian mass extinction. The persistence of similar calcimicrobial framestone horizons into the Upper Scythian suggests that detrimental environmental conditions associated with the extinction persisted until the end of the Scythian. Further study of these sections promises to provide constraints on causes of the extinction and the environments in the aftermath.

Remarkably different Late Permian–Early Triassic marine records are seen in sections from the western deep-water margin of Pangea (Ursula Creek, British Columbia) and the high paleolatitude, southern margin of the Neotethyan Ocean (Selong, South Tibet). The Ursula Creek section reveals the progressive decline of seafloor oxygen values in the Changxingian Stage (loss of bioturbation, authigenic U enrichment, appearance of pyrite framboid populations), followed by the persistent development of euxinic conditions in the latest Changxingian and throughout the Early Triassic; an event that coincides with the disappearance of a siliceous sponge fauna and the loss of diverse radiolarian populations. The Selong section, which was located on a distal passive margin, records regression and erosion in the mid-Changxingian, followed by a phase of deepening that began in the late Changxingian. The boundary interval is associated with a marked diversity increase due to the appearance of equatorial taxa (foraminifera, brachiopods, and sponges), suggesting warming without extinction in marine waters at high southern paleolatitudes. Only in the late Griesbachian Stage are the diverse Permian holdovers eliminated, again at a level showing evidence for dysoxia (thinly-bedded, authigenic U-enriched, pyrite-rich limestone). Thus, the end-Permian mass extinction is seen to be diachronous by half a million years or more, with late Changxingian extinction in Panathalassa coinciding with diversity increase associated the migration of warm-water taxa into the high southerly paleolatitudes regions of Neotethys.

How well does a death assemblage of marine mammal bones reflect the diversity, species composition, and proportion of bone types in the living fauna? Marine mammal remains were surveyed along the beaches of the Colorado River delta, Baja California, Mexico. Three carcasses and 470 bones were found among 112 localities along 4.0 km of shoreline. The location of each site was recorded and each bone was identified, photographed, and measured and its taphonomic condition was noted. The proportion of bone types found was compared to the proportions known in living marine mammals. The list of species found as bones was compared to the list of species known to live in the northern Gulf of California.

The maximum skeletal ratio of skull:vertebrae:ribs:phalanges:girdles/limbs in a typical Gulf of California marine mammal is 1:74:30:56:16. The 28 skulls and 442 post-cranial bones found provided a skeletal ratio of 1:12:3:1:1. Although vertebrae are the most common bones in the bone assemblage, only 316 were found, not the ∼2,000 predicted by the 28 skulls, indicating that vertebrae are under-represented. Therefore, skulls provide the best estimate of the minimum number of individuals. Smaller bones appear to be more easily destroyed, buried, or transported away. Most vertebrae were in good condition, suggesting that most bones arrived on the beach recently.

Remains of 8 of the 18 species recorded in the northern Gulf were found: Zalophus californianus (California Sea Lion, 8 skulls), Delphinus delphis (Common Dolphin, 7 skulls), Tursiops truncatus (Bottlenose Dolphin, 6 skulls), Phocoena sinus (Vaquita, four skulls), Pseudorca crassidens (False Killer Whale, one skull), Kogia breviceps (Pygmy Sperm Whale, one skull), and a possible Mesoplodon sp. (Beaked Whale, one skull). One Physeter macrocephalus (Sperm Whale) was identified by its large vertebrae.

Differences in population size, habitat use, and behavior among species may affect species composition and abundance within the bone assemblage. Migrants and rare species are not as abundant as residents in the bone assemblage. Coastal species are more common than oceanic ones.

Marine mammal remains are common within the 3% of Colorado Delta shoreline surveyed, and provide a remarkably good sample of the living fauna. Surveys of mammal remains may be a valuable and cost-effective supplement to aerial and nautical surveys of the live fauna.

Planktonic foraminiferal age of the Miocene sequence in the Iwadono Hills of central Japan is determined in reference to recent advances in Miocene planktonic foraminiferal biostratigraphy of Japan. The interval from the Godo through the Negishi to the lower part of the Shogunzawa Members of the Iwadono Formation yields 55 species of planktonic foraminiferal fossils. The Godo Member is assigned to planktonic foraminiferal zone N.8. The Negishi Member and the lower part of the Shogunzawa Member are confined to zones N.10 to N.13. Nine foraminiferal biohorizons were detected, seven of which enable us to determine a detailed age-thickness model for the sequence. The age-thickness model indicates a remarkably slow sedimentation rate in the Negishi Member (less than 9 mm/kyr). Furthermore, a relationship is established between the foraminiferal biostratigraphy and other stratigraphic data (diatoms, calcareous nannofossils, and radiometric ages) in the area. This relationship agrees well with the age-correlation chart of Japanese Neogene sediments.