Paleoecological Model Research Articles

The conodont biofacies model of shallow paleoenvironments in Frasnian (Late Devonian)

The article considers various criteria of the conodont biofacies distinguishing, and principles of conodont paleoecological models reconstructing. The proposed conodont biofacies model is based on conodont distribution in the Frasnian (Upper Devonian) of the Voronezh anteclise (Central regions of Russian Platform).

The structure of the nonmarine fossil record: predictions from a coupled stratigraphic–paleoecological model of a coastal basin

AbstractPresented here is a coupled model of the nonmarine fossil record, based on a geometric model of deposition, a random-branching model of evolution, and an ecological model based on an elevation gradient. This model provides testable predictions about the stratigraphy and fossil occurrences in coastal nonmarine settings under three scenarios of sea-level change. A slow relative rise in sea level causes a declining ratio of channel to floodplain deposits, plus changes in community composition that reflect an upward increase in elevation relative to sea level. A rapid relative rise in sea level drives increasing aggradation rates, decreases the ratio of channel to floodplain deposits, and triggers a shift from higher-elevation (more inland) to lower-elevation (more coastal) communities. A fall in sea level produces an unconformity, manifested by valleys separated by interfluves. The resumption of deposition following the sea-level fall causes an abrupt shift in community composition across the unconformity, reflecting the duration of the hiatus and the increased elevation relative to sea level. This produces a cluster of first and last occurrences at the unconformity, and it is the only sequence-stratigraphic source of such clusters in a nonmarine system, in contrast to the multiple mechanisms for generating these clusters in marine systems. A central prediction of these models is that the nonmarine fossil record preserves systematic changes in community composition that reflect elevation (or equivalently, distance from shore). Diagnosing these gradients in ancient systems is a promising avenue of future research.

The influence of Early Cretaceous paleoclimate warming event on sedimentary environment evolution and organic matter sources in Yin'e Basin: Evidence from petrology and molecular geochemistry

The lacustrine organic-rich fine-grained sedimentary rocks of the Early Cretaceous Bayingebi Formation are widely distributed in the Yin'e Basin and they have become important source rocks for oil and gas exploration. To reveal the influence of paleoclimate warming event on sedimentary environment evolution and organic matter sources, the petrological and molecular geochemical analyses of the upper member of the Bayingebi Formation (K1b2) were carried out using optical microscopy, X-ray diffraction, scanning electron microscopy, Rock-Eval pyrolysis and gas chromatography–mass spectrometry, in order to establish the paleoecological models of the Early Cretaceous freshwater and saline lakes. The oil shale and dark mudstone of K1b2 are both in the immature-early mature stage and have good potential for hydrocarbon generation, with a dominance of type I and type II1 kerogen. Two types of primary dolomite were found in this formation: microcrystalline dolomite with uniform structure, and the microbially originated spherical dolomite aggregates. The K1b2 can be divided into four units based on its lithology and logging curve characteristics. Unit II was deposited in the peak of lake development, under the warm-humid paleoclimate with abundant annual precipitation. There was greater influx of freshwater than other units, which resulted in the unstable stratification of the water column and less reducing condition of the lake bottom water body. Lower aquatic organisms and vascular plants were unprecedentedly prosperous, which were indicated by short-term thriving phenomena of telalginite, and the large input of terrestrial OM and highest abundance of the OM compared to other units. A lake water salinization event occurred during the sedimentation period of Unit III under the cooling climate, causing a transition from a freshwater lake to a high-salinity lake with reducing condition and stable stratification of the water column. Salinity of lake water increased the competitiveness of salt-tolerant algae and bacteria. The salty environment is beneficial for the thriving of single to halophilic genus of microorganism and lead to significantly lower abundance of telalginite. The biological sources of OM were mainly bacteria, algae and emergent plants, with limited contribution of terrestrial higher plants. The anoxic alkaline environment and high salinity condition at the lake bottom were beneficial for the formation of carbonate minerals and the preservation of OM. This were characterised by medium abundance of OM and high hydrocarbon generation potential. The study on the petrological and molecular geochemical characteristics of these organic-rich fine-grained sedimentary rocks is of great significance for investigating the genetic mechanisms and resource potential of oil and gas.

Occupancy models reveal regional differences in detectability and improve relative abundance estimations in fossil pollen assemblages

The late Quaternary fossil record provides crucial data that demonstrate how organisms respond to climate change. These records have been used to great effect, demonstrating that no-analog communities frequently occur during periods of no-analog climate, and that taxa demonstrate individualistic responses to change. However, our efforts to reconstruct biotic responses to environmental change are frequently hampered by inconsistent sampling and differential preservation of fossil taxa. We leveraged occupancy modeling methods and the fossil pollen record across eastern North America to identify circumstances under which occupancy modeling improves our ability to estimate relative abundance in four pollen taxa (Cornus, Fagus, Picea, and Pinus) through time (15 kya to present) and to identify localities where data are unreliable reflections of the local community. We found that integrating observed pollen abundance and detectability improves model performance. Low genus richness and large basin area were consistently important determinants of low detection. Our occupancy models were most informative for taxa with high enough variation in observed pollen abundance for models to be adequately calibrated. We combined occupancy model estimates of pollen abundance and detectability with a Getis-Ord statistical approach to identify spatial clusters of high or low detectability, identifying regions where a taxon’s pollen is more (or less) reliable. This work will advance the integration of ecological and paleontological sciences by allowing us to better identify whether a pollen taxon is truly absent from a fossil site or if it has simply gone undetected, allowing us to produce more robust paleoecological models. This approach will bolster our ability to identify the responses of plant communities to past climatic and anthropogenic change so that we can improve our predictions of future responses.

Fossil fern rhizomes as a model system for exploring epiphyte community structure across geologic time: evidence from Patagonia.

BackgroundIn extant ecosystems, complex networks of ecological interactions between organisms can be readily studied. In contrast, understanding of such interactions in ecosystems of the geologic past is incomplete. Specifically, in past terrestrial ecosystems we know comparatively little about plant biotic interactions besides saprotrophy, herbivory, mycorrhizal associations, and oviposition. Due to taphonomic biases, epiphyte communities are particularly rare in the plant-fossil record, despite their prominence in modern ecosystems. Accordingly, little is known about how terrestrial epiphyte communities have changed across geologic time. Here, we describe a tiny in situ fossil epiphyte community that sheds light on plant-animal and plant-plant interactions more than 50 million years ago.MethodsA single silicified Todea (Osmundaceae) rhizome from a new locality of the early Eocene (ca. 52 Ma) Tufolitas Laguna del Hunco (Patagonia, Argentina) was studied in serial thin sections using light microscopy. The community of organisms colonizing the tissues of the rhizome was characterized by identifying the organisms and mapping and quantifying their distribution. A 200 × 200 µm grid was superimposed onto the rhizome cross section, and the colonizers present at each node of the grid were tallied.ResultsPreserved in situ, this community offers a rare window onto aspects of ancient ecosystems usually lost to time and taphonomic processes. The community is surprisingly diverse and includes the first fossilized leafy liverworts in South America, also marking the only fossil record of leafy bryophyte epiphytes outside of amber deposits; as well as several types of fungal hyphae and spores; microsclerotia with possible affinities in several ascomycete families; and evidence for oribatid mites.DiscussionThe community associated with the Patagonian rhizome enriches our understanding of terrestrial epiphyte communities in the distant past and adds to a growing body of literature on osmundaceous rhizomes as important hosts for component communities in ancient ecosystems, just as they are today. Because osmundaceous rhizomes represent an ecological niche that has remained virtually unchanged over time and space and are abundant in the fossil record, they provide a paleoecological model system that could be used to explore epiphyte community structure through time.

Comment on “Does specialization imply rare fossil records of some benthic foraminifera: Late Palaeocene examples from the eastern Neo-Tethys (Meghalaya, NE India)” by Suman Sarkar [Palaeogeography, Palaeoclimatology, Palaeoecology 514 (2019) 124–134.

Sarkar (2019: Does specialization imply rare fossil records of some benthic foraminifera: Late Palaeocene examples from the eastern Neo-Tethys (Meghalaya, NE India) Palaeogeogr., Palaeoclimatol., Palaeoecol. 514, 124–134) uses the “first occurrences” of two large benthic foraminifera (LBF), namely Haymanella paleocenica Sirel and Keramosphaera iranica Rahaghi, in the upper lower Paleogene (Thanetian) Lakadong Limestone of NE India for far-reaching speculations on autecology and specialization as well as paleobiogeography and migration patterns in the central and eastern Neotethyan realm. [Note: The authors requested post-submission that all instances of “paleocenica” made in the Abstract and Introduction be altered to “elongata”.] We believe that the true occurrences of such taxa in Late Paleocene shallow-water carbonates from NE India are not only speculative but irrelevant because they are based on incorrect identifications. On the basis of such documentation, Sar19 claimed that the sparse occurrences of both species can be correlated to their specialist behavior. Sar19 also added a more specific interpretation of the paleoecology of H. elongata and K. iranica relating them to the upper and lower parts of the upper photic zone, respectively. This conclusion is, in our point of view, not supported by the data and also conflicts with a bulk of publications supporting the opinion that the autecology of LBF must be interpreted by means of comparative anatomy with recent counterparts along with taphonomy and a comprehensive facies analysis of the host carbonates.We will show that the taxon identified by Sar19 as Keramosphaera iranica instead is assigned to the Orduella spherica Sirel, whereas the identification of Haymanella paleocenica (elongata) from NE India remains unverified. We will also show how, contrary to what is claimed by Sar19, the paleoecological model proposed is not substantiated by data. Finally, we will argue that, in the Paleocene and lower Eocene of central and eastern Neo-Tethys, the identification of a biogeographic region must be regarded with a focus on the faunal exchanges established within the so-called ‘Lockhartia Sea’.

Cretaceous World TCN: Digitizing the Western Interior Seaway at the Yale Peabody Museum

Yale Peabody Museum (YPM) is a partner in the Western Interior Seaway Thematic Collections Network (TCN), along with the University of Kansas (lead) and seven other institutions (National Science Foundation Award # DBI-1601884). This project seeks to digitize the fossil organisms of the Western Interior Seaway, a shallow sea that covered inland North America from 100 to 65 million years ago. The resultant data will be a resource for K-16 education and will enable scientists to answer fundamental questions about the changing environment of a marine ecosystem during a key time in the history of life. The data generated will be ideal for use with an assortment of modern quantitative tools like paleoecological niche modeling (PaleoENM) and will help improve paleoclimate and paleoceanographic models. Less than two years into this three-year project, the YPM has digitized nearly 70,000 Cretaceous fossils from the seaway. Specimens are georeferenced and most have multiple images. To achieve project goals, we have overcome obstacles of digitizing multi-specimen concretions and foraminifera microslides by developing high-throughput digitization workflows that incorporate the open-source Inselect program and scripts to streamline image naming, image formatting, and uploading to our Axiell EMu collection management system. To facilitate use of the data in K-16 environments, an easy to use collections interface has been built using the iDigPaleo platform (idigpaleo.org). Cretaceous World (cretaceousworld.org) pulls data from iDigBio for all Cretaceous World TCN providers. Students can browse specimens using filters, rather than entering specific search terms. Navigation is simplified using common names harvested from the Encyclopedia of Life. Specimens are displayed as images accompanied by collection and locality data and plotted on a map. Registration provides access to tools supporting annotation, measurement, specimen record commenting, and social media sharing. Images can be curated as galleries and used for education. This includes sharing of galleries between students and teachers and PDF or PowerPoint exports. Fifty-eight 3D models of vertebrates and invertebrates have been placed on morphosource.org and will be made available via a 3D embedded viewer on cretaceousworld.org for use in K-16 education. Undergraduate students from Dartmouth, Oberlin, Southern Connecticut State University, and Yale, have participated in the project and served as mentors for high school interns. These interns, recruited from the Peabody EVOLUTIONS afterschool program, gained first-hand experience in collections-based research, digitization, and imaging techniques, while learning about the science of paleontology and the process of curating museum collections, and researching and reconstructing food webs in this fascinating ancient ecosystem.

E.M. van Zinderen Bakker (1907–2002) and the study of African Quaternary palaeoenvironments

The scientific contributions of E.M. van Zinderen Bakker (1907–2002) included the introduction of pollen analysis to Quaternary studies in South Africa. His palaeoecological theories evolved while performing palynological research in Southern Africa (the Maluti Mountains, Florisbad, Aliwal North, the Namib Desert), East Africa (Kalambo Falls, Mount Kenya, Cherangani Hills) and on the subantarctic islands (Marion and Prince Edward Islands). He was involved in the first radiocarbon dating from South Africa at Florisbad. Due to quantitative palynological studies he abandoned Wayland's (1929) Pluvial Theory that was generally accepted in the 1960s. He correlated observations of climate changes in Africa to data from marine borehole-cores and climatic fluctuations in the Northern Hemisphere. His observations led to the proposal that global temperature fluctuations are the primary cause of palaeoenvironmental changes. His studies culminated in a conceptual paleoecological model for the Last Glacial Maximum (LGM). Initially he based the model on symmetrical contraction of climatic belts about the equator that shifted the mid-latitude westerly wind system northward to increase the area receiving winter rainfall but later adjusted this by proposing a mechanism of westerly wind system intensification. He suggested that at this time grasslands had spread over wider areas in Southern Africa and that the tropical rain forests in the equatorial region fragmented. For interglacial periods he suggested that a southward shift of the Intertropical Convergence Zone (ITCZ) resulted in widespread humidity in the Congo Basin while large areas of the interior of Southern Africa became arid. Some of his ideas, especially his conceptual models of Quaternary vegetation and climate, are still relevant to the explanation of recent discoveries.

From past to future: impact of climate change on range shifts and genetic diversity patterns of circumboreal plants

Climate change is projected to influence the genetic resources of plant species. Recent research has examined genetic diversity patterns under current climate conditions, with little attention to the future genetic consequences for species. In this study, we combined ecological niche modeling and population genetic approaches to project future changes in genetic diversity using plastid and nuclear DNA and reconstructed distribution patterns of three circumboreal plants (Chamaedaphne calyculata, Linnaea borealis ssp. borealis, and Pedicularis sceptrum-carolinum ssp. sceptrum-carolinum) in the last glacial maximum. We found that circumboreal plants could potentially lose their geographic ranges in the future (2070; 35–52% in RCP 4.5 (representative concentration pathways), 37–53% in RCP 6.0, and 56–69% in RCP 8.5), only slightly compensated by a predicted range gain of 18–33% (across the three RCPs). It is expected that future genetic diversity level could remain similar or lower than the present level. On the other hand, the homogeneity of the genetic background—a lack of admixture and domination of one gene pool in most populations of C. calyculata and L. borealis ssp. borealis—was predicted to become more pronounced in the future. Combining the paleoecological niche modeling and genetic data revealed, more precisely, the climate refugia for circumboreal plants in the Alps, central Asia, Beringia, and southern North America and the macrorefugia more restricted to the northern part of Eurasia and North America, reaching the arctic zone.

Groundwater isotopic data as potential proxy for Holocene paleohydroclimatic and paleoecological models in NE Brazil

Holocene paleoclimatic patterns in NE Brazil are recognized to present singular characteristics when compared with the remaining tropical South-America. In particular, isotopic variations in speleothem calcite highlight that in contrast to the rest of tropical SA, NE Brazil experienced humid conditions during lower summer insolation, i.e. throughout the Early-Mid Holocene, and aridity when, as nowadays, summer insolation was high. In parallel, paleobotanical and palynological investigations suggest that these wetter conditions, also associated with colder climate, could have promoted the setting of ecological corridors between the current Amazonian (continental) and Atlantic (littoral) forests. In this context, this work aims at showing how groundwater isotopic data could be used as a complementary proxy to further explain these Holocene paleohydroclimatic and paleoecologic processes. By comparing δ18O, δ2H and d-excess of modern waters with Early-Mid Holocene groundwater in Recife (Pernambuco state, NE Brazil), differences in recharge patterns and moisture origin can be constrained. We find that Early-Mid Holocene waters present higher d-excess than the modern groundwater. Given that the Early-mid Holocene colder and wetter conditions (higher relative humidity) should lead to a reverse trend, i.e. lower d-excess, we hypothesize that the groundwater moisture sources was heavily recycled. Such a hypothesis would be consistent with the presence of a rainforest-type ecosystem, similar to the present Amazonian forest, in the currently arid NE Brazil. These observations highlight the potential added value of the groundwater isotopes proxy to discuss the interrelationships of paleohydrological and paleoecological patterns during the Early-Mid Holocene. These new proxies might allow the spatio-temporal extent of the above-mentioned ecological corridors to be discussed.

Pleistocene footprints show intensive use of lake margin habitats by Homo erectus groups

Reconstructing hominin paleoecology is critical for understanding our ancestors’ diets, social organizations and interactions with other animals. Most paleoecological models lack fine-scale resolution due to fossil hominin scarcity and the time-averaged accumulation of faunal assemblages. Here we present data from 481 fossil tracks from northwestern Kenya, including 97 hominin footprints attributed to Homo erectus. These tracks are found in multiple sedimentary layers spanning approximately 20 thousand years. Taphonomic experiments show that each of these trackways represents minutes to no more than a few days in the lives of the individuals moving across these paleolandscapes. The geology and associated vertebrate fauna place these tracks in a deltaic setting, near a lakeshore bordered by open grasslands. Hominin footprints are disproportionately abundant in this lake margin environment, relative to hominin skeletal fossil frequency in the same deposits. Accounting for preservation bias, this abundance of hominin footprints indicates repeated use of lakeshore habitats by Homo erectus. Clusters of very large prints moving in the same direction further suggest these hominins traversed this lakeshore in multi-male groups. Such reliance on near water environments, and possibly aquatic-linked foods, may have influenced hominin foraging behavior and migratory routes across and out of Africa.

Microfossils and biofacies of the Vendian fossil biota in the southern Siberian Platform

Based on the study of the litho- and biofacies of the Vendian Nepa Horizon in the central area of the Siberian Platform inland, a paleoecological model for the Vendian microbiota has been developed. The sedimentation environments of the Katanga saddle have been reconstructed, and three sedimentary systems have been recognized: (1) lower continental, formed by the deposits of proluvial fans and riverbeds of temporary streams; (2) middle transgressive, made up of littoral sand facies in the lower part and of fine-clastic shelf strata in the upper part; and (3) upper, of sea highstand, composed of alternating sand bank facies and fine-clastic lagoon deposits. Four biofacies have been recognized in the fine-terrigenous deposits of the Nepa Horizon: (1) Appendisphaera, represented by a Doushantuo-Pertatataka acanthomorph assemblage; (2) Transitional, with a great diversity of plankton and benthic (including complex) taxa; (3) Vanavarataenia, dominated by Vanavarataenia complex benthic algae; and (4) Oscillatoriopsis, represented by taxonomically poor biotas with morphologically simple (mainly prokaryotic) remains. These biofacies are confined to the following sedimentation environments: Appendisphaera is widespread in the distal open-sea areas; the Transitional biofacies is localized in the distal environments of the semi-isolated inner basin; Vanavarataenia occurs in the proximal areas; and Oscillatoriopsis is typical of the shallow-water environments, both extended (corresponding to the highstand period) and local.

Reconstruction of fire regimes through integrated paleoecological proxy data and ecological modeling.

Fire is a key ecological process affecting vegetation dynamics and land cover. The characteristic frequency, size, and intensity of fire are driven by interactions between top-down climate-driven and bottom-up fuel-related processes. Disentangling climatic from non-climatic drivers of past fire regimes is a grand challenge in Earth systems science, and a topic where both paleoecology and ecological modeling have made substantial contributions. In this manuscript, we (1) review the use of sedimentary charcoal as a fire proxy and the methods used in charcoal-based fire history reconstructions; (2) identify existing techniques for paleoecological modeling; and (3) evaluate opportunities for coupling of paleoecological and ecological modeling approaches to better understand the causes and consequences of past, present, and future fire activity.

Sites on the landscape: Paleoenvironmental context of late Pleistocene archaeological sites from the Lake Victoria basin, equatorial East Africa

Open-air archaeological sites record only a small fraction of the behavioral traces of mobile forager populations. Whereas caves and rockshelters were often occupied at least in part for protection from the elements, the reasons why human foragers occupied other places on the landscape (however briefly) are varied and not always readily recoverable. We develop a framework for interpreting human use of the landscape and modeling occupation of open-air sites using the archaeological and paleoenvironmental record of Middle Stone Age (MSA) sites from Rusinga and Mfangano Islands, located near the eastern margin of Lake Victoria. Paleoenvironmental reconstructions using fossil faunas suggest an arid grassland setting unlike the present. Paleoecological modeling of the habitats of extant and extinct bovids, combined with GIS-based reconstructions of lake level change, indicate that human occupation of these sites coincided with substantial declines in the level of Lake Victoria. During this time, both Rusinga and Mfangano would have been connected to the mainland and represented local topographic highs within an extensive grassland. Geological, ecological, and ethnobotanical observations suggest that these topographic high points would likely have been important sources of stone raw material, fresh water, and a variety of plant resources for food, fuel, and other purposes. In contrast, the grassy lowland plains were probably exploited primarily as a source of large game, which included numerous species of large gregarious grazers, several of which may have followed now extinct migration routes.

The role of glacial cycles in promoting genetic diversity in the Neotropics: the case of cloud forests during the Last Glacial Maximum

The increasing aridity during the Last Glacial Maximum (LGM) has been proposed as a major factor affecting Neotropical species. The character and intensity of this change, however, remains the subject of ongoing debate. This review proposes an approach to test contrasting paleoecological hypotheses by way of their expected demographic and genetic effects on Neotropical cloud forest species. We reviewed 48 paleoecological records encompassing the LGM in the Neotropics. The records show contrasting evidence regarding the changes in precipitation during this period. Some regions remained fairly moist and others had a significantly reduced precipitation. Many paleoecological records within the same region show apparently conflicting evidence on precipitation and forest stability. From these data, we propose and outline two demographic/genetic scenarios for cloud forests species based on opposite precipitation regimes: the dry refugia and the moist forests hypotheses. We searched for studies dealing with the population genetic structure of cloud forest and other montane taxa and compared their results with the proposed models. To date, the few available molecular studies show insufficient genetic evidence on the predominance of glacial aridity in the Neotropics. In order to disentangle the climatic history of the Neotropics, the present study calls for a general multi-disciplinary approach to conduct future phylogeographic studies. Given the contradictory paleoecological information, population genetic data on Neotropical cloud forest species should be used to explicitly test the genetic consequences of competing paleoecological models.

Methane-seep brachiopod fauna within turbidites of the Sinaia Formation, Eastern Carpathian Mountains, Romania

This study elucidates the paleoecology and paleobiogeography of the Early Cretaceous brachiopod Peregrinella known in museum collections from a few localities in Romania, supplemented with new material from a rediscovered locality first mentioned in the 1870s. Most Peregrinella fossils are enclosed in mass waste deposits, but at two sites authigenic limestones with assemblages of brachiopods preserved in life position have been recognized. Paleontological, petrographic, stable isotopic, and organic geochemical investigations of these brachiopod-bearing limestones from the Upper Sinaia Formation, Eastern Carpathian Mountains, Romania, confirm Peregrinella as having lived at methane seeps in a siliciclastic-dominated flysch basin. The seeps developed on the slope of the External Dacides Basin. The new collections of Peregrinella indicate that shells derived from contemporaneous intrabasin methane seeps and were transported downslope by turbidity currents. Previous paleoecological models that consider Peregrinella to be solely derived from transport downslope from shelf environments are questionable especially as Peregrinella has never been recovered from typical shelf faunas; in the instance documented here from the External Dacides Basin methane-seep faunas with Peregrinella are likely to be the origin of such allochthonous faunas. The Sinaia Formation was deposited in a deep-water marine basin, derived from an intracontinental rift that developed during Late Jurassic-Early Cretaceous extension. The fractured and faulted basin margin provided the backdrop for the development of the methane seepage and the associated fauna. Foraminifera from background sediments in the sequence with turbidites confirm a late Hauterivian to early Barremian age for Peregrinella within the Sinaia Formation. This is significant because it indicates that Peregrinella ranged through into the Barremian, whereas it has typically been considered to range only as high as the Hauterivian.

Ecological change and the extinction of the Levantine Neanderthals: implications from a diachronic study of micromammals from Amud Cave, Israel

It has been hypothesized that the climate shift associated with the Heinrich 5 event (H5) and the decrease in productivity throughout MIS 4 contributed to the demise of Neanderthals from the Levant. The Middle Paleolithic stratigraphic sequence of Amud Cave (Israel) spans MIS 4 and the transition to MIS 3 and contains Neanderthal skeletal remains as well as microfaunal assemblages, often used in the literature as reliable paleoecological proxies. This combination offers a unique case study to address the question of the effects of climate on Neanderthal population dynamics. Here we present a diachronic study of the rodent assemblages from Amud Cave, Israel, using taphonomic and nested hierarchical paleoecological models to test the hypothesis of a decrease in environmental productivity throughout the Amud sequence. Results suggest that there is no change in high-level presence–absence and rank abundance of rodent species throughout the sequence of Amud Cave, but there is change in low-level relative abundance of four taxa. Paleoecological analysis suggests that while all the stratigraphic sub-units of Amud Cave can be assigned to a Mediterranean biome, an apparent trend of decrease in grasslands proportions throughout the sequence is discordant with other regional paleoecological proxies. Taphonomic analysis reveals that this may be attributed to specific predator preferences of rodent prey, and thus does not reflect the true shift in paleoecology throughout the temporal sequence represented in the cave. The high-level overall stability in rodent community suggests that climatic shifts during the MIS 4–3 transition were of a magnitude that did not have a major impact on small mammals in the region. Such results are consistent with evidence from analysis of large mammal community and vegetal remains in Amud and contemporaneous Middle Paleolithic cave sites, and suggest that climate change may not have had the hypothesized effect on Neanderthal extinction in the Levant.

Looking for a Long-Term Record in the Greater Yellowstone Ecosystem: The 2010 Field Season at The Stinking Springs Rockshelter, Teton County, Wyoming.

The mountainous environment of northwestern Wyoming is not known for the preservation of organic remains, specifically that of vertebrate species. The paucity of vertebrate remains has hampered the ability of researchers to understand the evolution of the Quaternary mammalian community, which is in sharp contrast to the detailed understanding of the region’s geologic, climatic, and vegetation history. The few sites that have produced vertebrate remains have been largely confined to dry caves and rockshelters in the surrounding region and a few open air archaeological sites. In southern Teton County we have located a large rockshelter at the mouth of Hoback Canyon that presents a unique opportunity to recover a long-term mammalian record documenting Quaternary paleoecological change. Hand augering in 2006 revealed evidence of intact, datable strata likely to yield a robust mammalian faunal record. A radiocarbon age of 4210 ± 50 yrs BP was obtained from Ponderosa pine charcoal at a depth of 90 cm below surface, suggesting a record extending at least to the mid-Holocene. In 2010, the Utah State University Field School conducted limited controlled excavations in two 1m2 units. Excavations produced additional evidence of stratified deposits to a depth of 1.9 m. Remains recovered include lithic debitage, hearth features, faunal remains, and a possible large mammal processing area. Two specimens, one on Pinus charcoal from a depth of 1.9 m and a portion of a bighorn sheep mandible from 1.0 m, were submitted for radiocarbon assay. The ages are 4350 ± 25 yrs BP and 3360 ± 25 yrs BP, respectively. The size, geology, and setting above the Hoback River in a natural bottleneck between ungulate winter and summer ranges make the Stinking Springs rockshelter an excellent candidate for archaeological and paleoecological investigation. Proposed future investigations are designed to assess the rockshelter for the presence of preserved vertebrate remains and the deposit’s potential to address a number of key issues of how the mammalian community developed during the Quaternary in relation to large-scale (e.g., glaciation) and small-scale climatic (e.g., post-glacial maximum warmth, Little Ice Age) shifts. The anticipated record will not only provide information on the mammalian community structure, but will also provide a paleoecological model for understanding the economies of precontact Native American groups who lived in the region, and will also provide key information that can be applied to future management of threatened species and their habitat (e.g., pronghorn antelope).

Assessing hypolimnetic oxygen concentrations in Canadian Shield lakes: Deriving management benchmarks using two methods

The ability to predict hypolimnetic dissolved oxygen concentrations in lakes and to track changes in concentrations over time in response to known environmental stressors is critical for effective lake management. The background concentrations of deepwater oxygen, in particular, provide important management benchmarks for assessing the impact of current and future shoreline residential development on water quality. Background can be defined as the conditions that exist in the absence of, or prior to, human influence. We compare 2 models commonly used to predict end-of-summer, volume-weighted hypolimnetic oxygen (VWHO) concentrations in Canadian Shield lakes. The paleoecological and empirical models are evaluated in their ability to predict present-day VWHO concentrations, and then compared in their predictions of background VWHO concentrations and in predictions of changes in VWHO from background to present-day conditions. The predictive power of the 59-lake paleoecological model (jackknifed r2 = 0.51, RMSEP = 2.18 mg/L) is comparable to other models that have used chironomids to predict the degree of hypolimnetic anoxia in lakes but is lower than that produced by the empirical modelling approach (r2 = 0.87, SE = 1.04 mg/L). However, this discrepancy may be offset by the enhanced realism of the paleoecological model, including its ability to predict declines in VWHO over time. The combined use of the paleoecological and empirical modelling approaches may allow lake managers to examine changes in deepwater oxygen concentrations in response to a single “targeted” stressor (e.g., residential shoreline development) and to multiple environmental stressors (e.g., climate change, hydrological management).

SHALLOW-WATER SPOROLITHON RHODOLITHS FROM NORTH ISLAND (NEW ZEALAND)

Abstract Shallow-water Sporolithon rhodoliths from New Zealand are described here on the basis of shape, size, composition, internal structure, and major taphonomic attributes, with the aim of discussing their significance in the framework of current ecological and paleoecological models of rhodolith formation and accumulation. The very shallow water environment (<2 m) of the Whangaparaoa Peninsula undergoes daily tidal currents and seasonal storm conditions. These factors, along with the availability of cobbles and pebbles as suitable substrate, lead to the accumulation of spherical, fruticose, monospecific, nucleated, and internally compact rhodoliths. The observed taphonomic features include apical abrasion, intercalary growth of protuberances after mechanical breakage, and multiple growth stages with distinctive bioerosion (by bivalves, annelids, and cyanobacteria), which are identified by internal abrasion surfaces and dark layers. A review of the pattern of global distribution of the coralline gener...