The effect of seasonal rainfall on nutrient input and biological productivity in the Yax Chen cave system (Ox Bel Ha), Mexico, and implications for μXRF core studies of paleohydrology Publication date: 15 November 2019 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 534 Author(s): Chelsi A. McNeill-Jewer, Eduard G. Reinhardt, Shawn Collins, Shawn Kovacs, Winnie May Chan, Fred Devos, Chris LeMaillot Abstract Lakes and speleothems from Mexico's Yucatan Peninsula have been used extensively over the past decades for paleoclimate studies, however aquifer condition and its response to climate change has received little attention. Cenotes (sinkholes) and coastal caves have been shown to record the paleohydrology of the aquifer, but there is little information on sedimentation in these cave systems and its response to climate change. Newly developed μXRF instrumentation for the analysis of cores can achieve subannual resolution due to small measurement increments, but short period studies examining weathering inputs and rainfall have not yet been undertaken, hindering paleoenvironmental interpretations of lake and cave sediment records. This study examines the spatial and temporal relationship of cave sediment geochemistry in the anchialine cave system of Yax Chen (Quintana Roo, Mexico). Sediment traps (n = 51) were placed at seventeen stations along the 2.7 km flooded cave system, which transitions from mangrove to upland forest terrain, with cenotes of variable size and frequency along its length. Sediment traps were collected every ~6 months from May 2013–May 2017 along with rainfall and groundwater level data. There are distinct responses of lithogenic (Fe, Ti, Sr - limestone weathering) and biogenic influenced (Si, K, S - phytoplankton and mangrove sediment) elements in the sediment samples associated with seasonal rainfall and hurricanes. While lithogenic elements (Ti/K) show a direct relationship seasonal rainfall, the sedimentation of biologically influenced (Si/Ti) elements exhibit a 6–12 month lagged response with large rainfalls such as Hurricane Ingrid in 2013 and other tropical storms throughout the study period.

Multiple skeletal and dental pathologies in a late Miocene mesotheriid (Mammalia, Notoungulata) from the Altiplano of Bolivia: Palaeoecological inferences Publication date: 15 November 2019 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 534 Author(s): Marcos Fernández-Monescillo, Pierre-Olivier Antoine, Bernardino Mamani Quispe, Philippe Münch, Rubén Andradre Flores, Laurent Marivaux, François Pujos Abstract We report a partial adult skeleton of the notoungulate mesotheriid Plesiotypotherium achirense, showing multiple skeletal and dental pathologies, from the late Miocene locality of Achiri, Bolivian Altiplano. The material shows bilateral absence of hypselodont permanent molars, further associated with exostosis on various limb bones. The main pathology relates with the loss of two first molars on both sides of the jaw, perhaps due to long-lasting periodontal diseases. Other craniomandibular afflictions, likely related to the latter pathology, are an overgrowth of two first upper molars on both sides and the anomalous development of masticatory muscle insertions (m. masseter, pterygoideus medialis, temporalis, and temporalis pars profundis). A hypothetical pathological sequence of the masticatory apparatus was reconstructed according to distinctive wear of ever-growing crowns of two first upper molars and the unequal lower alveoli reabsorption. Additional pathologies are exostoses observed on several articular surfaces of limb bones, from the scapula to distal phalanges. They likely decreased the range of movements during locomotion of this individual. Given its multiple pathologies, we might have expected this abnormal individual to be a potential easy prey. However, the long-time survival of this animal suggests a low predatory pressure, a hypothesis that is consistent with the virtual absence of carnivorous vertebrates in the Achiri fossil assemblage and the composition of coeval mammalian guilds in the Bolivian Altiplano and/or a herd behaviour for Plesiotypotherium achirense, as seen in many modern grazing herbivore ungulates.

Paleohydrological changes in southeastern China from 13.1 to 2.5 ka based on a multi-proxy peat record Publication date: 15 November 2019 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 534 Author(s): Xinxin Wang, Xianyu Huang Abstract Investigating the hydrological changes in the East Asian monsoon regions of China during the Holocene could provide important insights into the mechanism and future variability of the East Asian summer monsoon (EASM) rainfall. However, existing studies have revealed large inconsistencies in the spatiotemporal pattern of the hydrological changes in East China, probably due to different climatic sensitivities of various proxies, the uncertainties of sedimentary chronologies and unevenness of proxy record distributions. Thus, multi-proxy records with precise dating are needed, especially in southeastern China which is one of the key places to determine the spatiotemporal pattern with few hydrological records available. In this study, hopanoid flux, humification degree, the concentration of total organic carbon (TOC) and the atomic ratio between total organic carbon and total nitrogen (C/N) of organic matter were applied on Shuizhuyang (SZY) peat cores retrieved from southeastern China to reconstruct the paleohydrological changes spanning from 13.1 to 2.5 ka. Results of these proxies reveal a moderately dry period during 13.1–11.6 ka, followed by an interval of increasing aridity from 11.6 to 8.6 ka. The Holocene optimum (referred here as an effective moisture maximum) occurred at 8.6–4.4 ka before the climate became drier from 4.4 to 2.5 ka. The hydrological changes in SZY during the Holocene with a mid-Holocene Holocene optimum are consistent with the regional climate records in southeastern China. Such an overall arid-wet-arid pattern in Southeast China during the Holocene closely tracked the variations in the west-to-east sea surface temperature (SST) gradient in tropical Pacific. We preliminarily concluded the ENSO state and the western Pacific subtropical high (WPSH) position associated with variations in the thermal state of the tropical Pacific were primarily responsible for the hydrological changes in Southeast China during the Holocene. Our study added new evidence to the spatiotemporal pattern of hydrological changes in eastern China during the Holocene.

Thermal maturity of carbonaceous material in conodonts and the Color Alteration Index: Independently identifying maximum temperature with Raman spectroscopy Publication date: 15 November 2019 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 534 Author(s): Rhy McMillan, Martyn Golding Abstract The Color Alteration Index (CAI) of conodont specimens is commonly used for identifying the maximum temperature to which units of sedimentary rock, particularly carbonates, have been heated. Observable color variations in these fossils are thought to be a result of the thermally-induced structural evolution of organic carbonaceous matter (CM). Such temperature history information is extremely valuable for applications in hydrocarbon exploration as well as for constraining other temperature-related geological processes in sedimentary systems. However, the identification of CAI depends on the qualitative visual assessment of color, which, along with a host of other potential complications, may yield inaccurate determinations of maximum temperature. Raman spectroscopy allows thermally-induced structural changes in CM to be quantified, and it has been used to estimate the thermal maturity in metasedimentary rocks for almost two decades. Here, we use Raman spectroscopy of carbonaceous material (RSCM) in conodont specimens and their Mississippian to Upper Triassic host rocks from British Columbia, Canada, to estimate maximum temperatures based on the transformation (structural reorganization) of disordered carbon to graphite. This study demonstrates that the maximum temperatures experienced by conodont specimens, as calculated from RSCM using the Iterative Fitting of Raman Spectra (IFORS) technique, correlate well with CAI but lie outside the suggested ranges in some instances. This may be due to complex thermal histories of these conodont specimens or the influence of diagenetic alteration, not thermal histories, on conodont color. We recommend the application of Raman spectroscopic analyses of CM in conodonts and their host rocks to obtain more confident, accurate, and precise estimations of maximum temperature that are independent of CAI.

Insect trace fossils elucidate depositional environments and sedimentation at a dinosaur nesting site from the Cretaceous (Campanian) Two Medicine Formation of Montana Publication date: 15 November 2019 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 534 Author(s): William J. Freimuth, David J. Varricchio Abstract We describe the diversity and abundance of insect (specifically hymenopterans and coleopterans) pupation structures in the Upper Cretaceous (Campanian) Two Medicine Formation at the Egg Mountain locality, western Montana, U.S.A., an important dinosaur nesting site. The study interval comprises a massive calcareous siltstone and indurated silty limestone horizons interpreted as the product of cumulative paleosols. A 7 m by 11 m area was quarried with a jackhammer at intervals of 12.5 cm thickness for a 1.5 m thick stratigraphic section. The ichnoassemblage comprises four morphotypes (small, medium, large, and wide) assigned to Fictovichnus sciuttoi, of which three represent wasp (hymenopteran) cocoons while the fourth (wide) type potentially was produced by a coleopteran. Medium and small F. sciuttoi are dominant while large and wide Fictovichnus are less common and absent in some sample intervals. Other probable insect traces include partial perforations in cocoons (Tombownichnus), isolated burrows, and an enigmatic hemispherical trace. Material is representative of a depauperate Celliforma ichnofacies. Pervasive cocoons and other traces throughout the sequence suggest persistent soil conditions suitable for insect nesting and pupation, and suggest an absence of sediment pulses of sufficient thickness to prohibit thorough colonization. Peaks in pupation chamber abundance may reflect episodes of reduced sedimentation rates otherwise unseen in the absence of primary bedding structures. Well-drained and friable soil conditions favorable for insect nesting also may help explain the abundance of dinosaur nests and other vertebrate nesting events in associated strata as well as the presence of small terrestrial forms.

Oxygen isotope analyses of ungulate tooth enamel confirm low seasonality of rainfall contributed to the African Humid Period in Somalia Publication date: 15 November 2019 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 534 Author(s): Rachel E.B. Reid, Mica Jones, Steven Brandt, Henry Bunn, Fiona Marshall Abstract During the African Humid Period (AHP), between ~14 and 5 ka, north and eastern Africa were much wetter and greener than they are today. Although the AHP has long been attributed to an increase in rainfall driven by orbital forcing, many details regarding the timing, pacing, and contributing moisture sources remain to be determined, especially for eastern Africa. Recent research suggests that both Atlantic and Indian Ocean moisture contributed to the AHP in eastern Africa. Large mammalian faunas from two Late Pleistocene/Holocene rockshelter sites in southern Somalia, Gogoshiis Qabe and Guli Waabayo, provide an unusual opportunity to investigate the AHP in an area of eastern Africa that is orographically isolated from Atlantic Ocean moisture. To track changes in aridity at these sites, we used the oxygen isotope aridity index, which exploits the difference in tooth enamel oxygen isotope (δ18O) values between evaporation insensitive obligate drinkers and evaporation sensitive non-obligate drinkers to calculate a water deficit value. Water deficit values calculated from dik-dik (Madoqua spp.; non-obligate drinkers) and warthog (Phacochoerus spp.; obligate drinkers) tooth enamel δ18O values at Gogoshiis Qabe and Guli Waabayo are in agreement and progressively increase toward the present. Additionally, two of three direct dated serially-sampled warthog teeth (ID 4032 and 4033) from Guli Waabayo demonstrate low seasonality of rainfall during much of the AHP (range in δ18O ≤ 1.8‰). One tooth (ID 4035) with high amplitude variability in δ18O values (3.1‰) dates to 8470 ± 66 cal yr B.P., a period identified as a lowstand in several lake level records. Our results suggest that regions isolated from Atlantic Ocean moisture likely experienced a less-pronounced AHP than those receiving moisture from multiple sources but indicate less seasonal variability than present. Our findings also support the presence of climate variability within the AHP.

Palaeoecology and palaeoclimatic context of Romanian Carpathian MIS 3 cave bears using stable isotopes (δ13C and δ18O) Publication date: 15 November 2019 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 534 Author(s): Marius Robu, Jonathan Wynn, Cristina Montana Puşcaş, Ioana Nicoleta Meleg, Jeremy E. Martin, Silviu Constantin Abstract Millimeter-scale growth rings in canine dentine of MIS 3 cave bears have been interpreted as annual growth bands produced, in part, by seasonal variation in growth rate. We present new intra-tooth stable carbon (δ13C) and oxygen (δ18O) isotope profiles in dentine hydroxylapatite of early forming permanent teeth, from three famous Late Pleistocene cave bear sites from Romanian Carpathians. We measured δ13C and δ18O of the CO3 fraction of dentine hydroxylapatite from samples covering a profile across the root, representing a general line from juvenile period to adulthood. Carbon isotopes measured in dentine samples – from the first to the last to be deposited – of the same individual, record an increase in δ13C values throughout immature life of bears as has been shown previously, with lower precision, using age categories. For the first time, based on δ13C data analysis, the weaning process in cave bears was identified. The δ18O values show substantial variations related, most probably, to seasonal growth of the dentine. Finally, the CO3 of dentine apatite extracted from cave bear canines proves to be reliable for geochemical analyses, reflecting physiology, behavior and palaeoclimatic conditions.

Diatom-inferred ecological responses of an oceanic lake system to volcanism and anthropogenic perturbations since 1290 CE Publication date: 15 November 2019 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 534 Author(s): David Vázquez-Loureiro, Vítor Gonçalves, Alberto Sáez, Armand Hernández, Pedro M. Raposeiro, Santiago Giralt, María J. Rubio-Inglés, Valentí Rull, Roberto Bao Abstract The impacts of natural- and human-induced processes on lake ecosystems in remote oceanic islands remain to be fully elucidated. These lakes are excellent candidates to analyze the importance of anthropogenic vs. natural forces driving lacustrine long-term ecological evolution from previous pristine pre-colonized conditions. Disentangling the effects of both is particularly relevant in highly active volcanic areas, where catastrophic eruptions can act as an atypical natural driver altering the lake's long-term ecological trajectories. In this paper we study past ecological changes occurring in Lake Azul (São Miguel island), a crater lake from the remote Azorean archipelago, to address which were the main causes of its long-term trophic history. We analyzed diatom assemblages, sedimentology, and bulk organic matter of sediments deposited since ca. 1290 CE, when a huge local eruption occurred. This episode drove the evolution of Lake Azul through six distinct phases, commencing with a restart of ecological succession after tephra deposition disrupted biogeochemical cycling. The alteration was so profound that the lake underwent a state of oligotrophic conditions for approx. 650 yr. Nutrients were sourced by fish-induced internal recycling and the overflow of the near Lake Verde during this period, rather than by allochthonous nutrient inputs modulated by climate variability and/or vegetation cover changes in the watershed after the official Portuguese colonization. It was only after recent artificial fertilization when the system overcame the volcanic-induced long-term resilience. This over-fertilization and a reduction in water turnover exacerbated the recent symptoms of eutrophication after 1990 CE. Contrary to other studies, Lake Azul constitutes an uncommon case of long-term resilience to trophic change induced by a cataclysmic volcanic eruption. It brings new insights into the fate of lake ecosystems which might be affected by similar events in the future.

Multiproxy dietary trait reconstruction in Pleistocene Hippopotamidae from the Mediterranean islands Publication date: 1 November 2019 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 533 Author(s): Elehna Bethune, Thomas M. Kaiser, Ellen Schulz-Kornas, Daniela E. Winkler Abstract Geographically isolated insular species face energetic restrictions and commonly evolve adaptations that distinguish them from their mainland ancestors. During the Pleistocene, several Mediterranean islands were inhabited by now extinct Hippopotamidae. They underwent diverse changes in locomotion, dentition and body size. Based on these differences, it is supposed that they occupied different ecological niches depending on their respective faunal complexes and available resources. In this paper, we assess the paleoecology of dwarfed hippopotami from Crete, Malta, Sicily and Cyprus using a novel dental multiproxy approach. We applied dental topography analysis (SAGA-GIS) to measure the mean slope of the dental occlusal surface, mirroring dietary adaptations, as well as 3D surface texture analysis (3DST) to quantify the surface of occlusal wear facets, which correlate with dietary abrasiveness. Low slope values were found in the larger, more hypsodont hippopotami, whilst the smaller Phanourios minordisplayed the highest occlusal relief with large compression basins. Since Hippopotamus pentlandi exhibited lower mean slope values than the larger, more hypsodont Hippopotamus amphibius, we conclude that lower occlusal reliefs reflect adaptations to lower diet quality and arid environments, which are characteristic of freshwater-limited island habitats. The 3DST analysis revealed distinct ecological niches for the investigated insular hippos. Hippopotamus creutzburgi exhibited enamel surface textures analogous to those of Hippopotamus amphibius, a fresh grass grazer, thus confirming a semiaquatic lifestyle at the upland lake at Katharo, Crete. Hippopotamus pentlandi was bound to a similar niche to the extant form, probably due to the mainland character of its fauna, but experienced more dust intake. Hippopotamus melitensis had to cope with high ingestion of abrasives, seemingly on account of a more generalistic diet in its resource-limited and small habitat. Results point to either Phanourios minor broadening its dietary niche in its almost competition-free habitat, or suggest a dietary shift following a climatic change. The adopted multiproxy approach proved to be useful in identifying dental adaptations and individual foraging strategies linked to energetically restricted habitats, and therefore contributes to a better understanding of basic evolutionary and ecological principles.

Rare colonial corals from the Upper Ordovician Kope Formation of Kentucky and their role in ephemeral invasions in the Edenian Publication date: 1 November 2019 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 533 Author(s): Felicia Harris, Heather Alley, Ron Fine, Bradley Deline Abstract A large colonial rugose coral was recently discovered as float partially buried beneath several inches of sediment in the Kope Formation of northern Kentucky. Corals are unreported in the Kope assemblage, not appearing until much later during the C4 and C5 sequences during the Richmondian Invasion, a period in which the area was inundated with invasive taxa migrating from the midcontinent. The slab contains the remains of several other species that are diagnostic of the Kope Formation, such as the brachiopods Sowerbyella rugosa and Zygospira cincinnatiensis. The large colonial rugose coral is composed of corallites ranging in diameter from 3 to 5 mm containing 10–14 twisting major septa with crenulated walls, which is consistent with Cyathophylloidescf. C. burksae. New taxa or new occurrences in a well-sampled formation, such as the Kope Formation, are unexpected especially for large skeletonized taxa, and highlights the rarity of coral within the assemblage. The Richmondian Invasion is linked to a transgressive event that increased connectivity between marine biogeographic provinces, disrupted ecosystem structure as well as acted as a significant evolutionary driver during the late Ordovician in the Cincinnatian faunal assemblages. Isolated dispersal events may have brought planktonic larva onto the Cincinnati Arch much earlier during transgression in the C1 sequence. The failure of the coral to become established might be linked to the low abundance of larva entering the region or non-ideal environmental conditions. The discovery of this coral in the Kope Formation further indicates the occurrence of rare and ephemeral dispersal events that have recently been reported within brachiopods.