Description: Publication date: 15 September 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 505 Author(s): Libin Wu, Xiaodong Liu, Liqiang Xu, Pingqing Fu, Xueying Wang, Jing Jin, Zixuan Rao, Yongli Zhou, Yeling Li Tropical seabirds play a key role in coral island ecosystems, but there are still many uncertainties regarding their paleoecology. Seabird paleoecology was investigated on Nandao Island, Xisha Islands, South China Sea, from sub-fossil remains spanning the past 800 years. Ornithogenic sediments were collected beneath seabird-inhabited shrubs where a large number of seabird/fish sub-fossils were recovered. We used reflectance spectroscopy to show that seabird population size was overall higher during the Little Ice Age (LIA) compared to periods before and after this event. Nonetheless, the number of seabirds also fluctuated during the LIA. Seabird populations on Nandao reached their highest points at 1480–1550 and 1650–1800 CE, respectively, but the population remained low from 1550 to 1650 CE. A large migration of seabirds from Nandao Island to the adjacent Beidao Island, where the population size surged at that time, is hypothesized to explain the corresponding decrease in the seabirds at Nandao. Stable isotope (δ 15 N and δ 13 C) analyses also suggest a change in foraging behavior by seabirds at Nandao during the period 1550–1650 CE. Seabirds at low population size foraged near the island and preyed upon smaller flying fish as inferred from low δ 15 N and high δ 13 C values in fish scales, but fed upon larger flying fish farther from the island during times of high population. This shift in foraging behavior is in accordance with predictions for Ashmole's Halo in that islands with high densities of birds will cause a depletion of resources near the colonies and force more distant foraging away from the colony.

Description: Publication date: 15 September 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 505 Author(s): Maria Rivera-Araya, Suzanne Pilaar Birch Oxygen and carbon isotopes from herbivore teeth have previously been used as paleoenvironmental proxies. However, their use in white-tailed deer ( Odocoileus virginianus ) remains rare. Here, we present the results of analysis of sequential sub-samples from second and third molars of wild and non-wild deer from Georgia, United States in order to assess their application in humid subtropical climates. In wild deer, enamel carbonate δ 18 O corresponds broadly to the recorded precipitation δ 18 O over the 10-month period of tooth formation, capturing the rainfall seasonality across the physiogeographic regions of the state. Non-wild deer show significantly lower values compared to both measured and modeled δ 18 O precipitation. While δ 13 C in tooth enamel carbonate appears to reflect diet, it does not reflect seasonality in either population. The δ 13 C and δ 15 N from bone collagen values suggest that diet and source of drinking water influence the potential of white tailed deer tooth enamel carbonate to record the δ 18 O seasonality in the study area; therefore, special attention on the provenance of deer are necessary for obtaining accurate paleoclimate reconstruction.

Description: Publication date: 15 September 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 505 Author(s): Tomi P. Luoto, Antti E.K. Ojala Arctic freshwater basins are diversity hotspots and sentinels of climate change, but their long-term variability and the environmental variables controlling them are not well defined. We examined four available lake sediment sequences from High Arctic Svalbard for their subfossil Chironomidae communities, biodiversity and functional traits and assessed the influence of climatic and limnological variability on the long-term ecological dynamics. Our results indicated that collector-filterers had an important role in the oligotrophic sites, whereas collector-gatherers dominated the nutrient-enriched sites with significant bird guano inputs. In the oligotrophic sites, benthic production, taxon richness and taxonomic and functional diversity were highest during the early Holocene, when temperatures showed a rapid increase. An increase in subfossil abundance and diversity metrics was also found in recent samples of the oligotrophic sites, but not in the bird-impacted sites, where the trends were decreasing. When partitioning out the environmental forcing on chironomid communities, the influence of climate was significant in all the sites, whereas in-lake production (organic matter) was significant in two of the sites and catchment erosion (magnetic susceptibility) had only minor influence. The findings suggest that major changes in Arctic chironomid assemblages were driven by climate warming with increasing diversity in oligotrophic sites, but deteriorating ecological functions in environmentally stressed sites. We found that although taxonomic and functional diversity were always coupled, taxonomical and functional turnovers were coupled only in the oligotrophic sites suggesting that the ecological functions operated by chironomids in these low-productivity sites may not be as resilient to future environmental change.

Description: Publication date: 15 September 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 505 Author(s): A.A. Vela-Pelaez, N. Torrescano-Valle, G.A. Islebe, J.F. Mas, H. Weissenberger Holocene fossil pollen samples ( n  = 38) from Lake Silvituc in Mexico were analyzed with the analog technique using modern pollen samples ( n  = 98) of the Yucatán Peninsula, Mexico. Calculated dissimilarity indices allow us to reconstruct the vegetation and to develop a precipitation record for the last 7900 years. The Middle Holocene shows a gradual increase of precipitation and a marked drop in reconstructed precipitation around 4200 BCE. During the Late Holocene two phases were identified: Phase I (2500 BCE – 1 CE) shows the greatest increase in precipitation with four peaks around 1200 BCE, 650 BCE, 200 BCE and 1 CE. Also a period of increased precipitation resulted for the period between 200 and 500 BCE. Periods of reduced precipitation were detected at 900–1100 BCE, 500–600 BCE and 100–190 BCE. Phase II (1–2000 CE) encompasses several strong dry events during the following periods: 150–300 CE, 750–900 CE, 1050–1180 CE, and 1530–1580 CE. A strong reduction of 32% in precipitation in the late Preclassic Period (100–300 CE) was detected. Non-analogs of Phase II are associated with periods of reduced precipitation and fall into time periods of extended droughts related to the Maya Late Classic and the Little Ice Age. A limiting factor on the use of analogs for tropical forests is that a combination of different analogs for the same fossil pollen signal exists. Interpretation under these circumstances requires good knowledge of the ecology of the taxa and a priori characterization of the modern samples.

Description: Publication date: 15 September 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 505 Author(s): Elver Luiz Mayer, Leonardo Kerber, Ana Maria Ribeiro, Alex Hubbe A recurrent aspect of the fossil record is the observation of a disproportionate number of specimens or individuals of a single taxon in some deposits, which is stated as dominance. Commonly, the dominance is explained as the result of catastrophic or short-term mass death events or are proxies for palaeoecological inferences regarding gregariousness. However, taphonomic, stratigraphic and chronologic analyses of fossiliferous deposits have shown that this is not always true. To contribute to the study of dominance in fossil assemblages, we describe a probable Quaternary skeletal accumulation dominated by the extant gregarious rock-dwelling rodent Kerodon rupestris recovered from Sumidouro do Sansão, a 65 m deep pitfall cave in northeast Brazil, and discuss the palaeoecological implications of our findings. We provide taxonomic identification, taphonomic analyses, and chronological assessment. Besides K. rupestris (minimum number of individuals, MNI = 35), we recorded three taxonomic groups, that are the ground sloth Catonyx cuvieri (MNI = 1), the anteater Tamandua tetradactyla (MNI = 1), and the cougar Puma concolor (MNI = 1). The taphonomic analysis of the K. rupestris remains supports the idea that entrapment of individuals was the main process of bone accumulation and that the death of cave inhabitants followed by short transport to the main hall possibly occurred. Kerodon rupestris remains persisted on the surface of the cave deposit for different time spans and were exposed to fragmentation, weathering, invertebrate boring and encrustation inside the cave environment. Direct dating suggests differences in the ages obtained and intermittent deposition of the individuals inside the cave. It highlights the influence of taphonomic controls on gregarious taxa, such as K. rupestris , towards dominating attritional time-averaged assemblages. Furthermore, it demonstrates that such assemblages do not necessarily support inferences about single event mortality and gregariousness of the dominant taxon. Graphical abstract

Description: Publication date: 15 September 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 505 Author(s): Yangyang Zhong, Huaichun Wu, Yuandong Zhang, Shihong Zhang, Tianshui Yang, Haiyan Li, Liwan Cao Establishing a high-precision numerical geological time scale for the Paleozoic Era remains a considerable challenge. In this study, we conducted detailed cyclostratigraphic analysis on the Middle Ordovician of the Huangnitang section and the core Changjin 3 (CJ-3), Zhejiang Province, South China. Magnetic susceptibility (MS) series were obtained from a total of 3909 discrete samples and are used as a paleoclimate proxy indicative of variations in detrital input of magnetic minerals. Power spectral analyses show that both the section and core have recorded an excellent hierarchy of Milankovitch cycles of 405 kyr, 101–135 kyr, 31–34 kyr, and 15.8–21.3 kyr. An integrated floating astronomical time scale (ATS) for the section and core was established according to the extracted stable 405-kyr eccentricity cycles. This new floating ATS suggests that the durations of the Darriwilian and Dapingian stages were 8.38 ± 0.4 Myr and 1.97 ± 0.7 Myr, and the durations of complete graptolite zones of the Middle Ordovician were precisely estimated. The ratios of band (obliquity or short eccentricity) power to total power reveal periodicities of ~1.2 Myr for the s 4 – s 3 term and ~1.9 Myr for the g 4 – g 3 term, and ~1.2-Myr obliquity cycles may have controlled global third-order eustatic sequences during the late Darriwilian.

Description: Publication date: 15 September 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 505 Author(s): Dan C. Jipa

Description: Publication date: 15 September 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 505 Author(s): Gildas Merceron, Marc Colyn, Denis Geraads Today, the family Giraffidae is restricted to two genera endemic to the African continent, Okapia and Giraffa , but, with over ten genera and dozens of species, it was far more diverse in the Old World during the late Miocene. We attempt to describe here how several species may have shared feeding resources in the Eastern Mediterranean. Dietary preferences were explored by means of Dental Microwear Textural Analysis in combination with estimation of body mass and the maximum height at which the various species were able to browse. One of our main results concerns the modern okapi, Okapia johnstoni . It is a forest dweller usually regarded as a browser, but we show that it might also forage on tough plants, possibly herbaceous monocots. Such feeding habits including portions of herbaceous monocotyledons were also found for some extinct species, especially the genera Samotherium and Palaeotragus . Palaeogiraffa shows a contrasted pattern: the specimens of P. pamiri from a site in Thrace were leaf-dominant browsers whereas those belonging to P. major and P. macedoniae from the Axios valley in Greece ingested herbaceous monocotyledons. Helladotherium duvernoyi , the only sivatheriine analyzed here is described as a leaf-dominant browser. The giraffine Bohlinia attica also falls within the leaf-dominant browser category but could browse on higher foliages than H. duvernoyi . On the whole, the reconstructed diets confirm the relationship between more grazing habits and smaller premolars, but not with higher dental crown height.

Description: Publication date: 15 September 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 505 Author(s): Tian Ying, David Shaw, Simon Schneider Sediments of the long-lived Lake Nanning in southern China (Guangxi Province) have yielded rich and diversified fossil biota of Oligocene age. The history of research on these fossils is documented herein, and revised lists of the flora and fauna recorded from Lake Nanning are provided. Based on newly collected data, the mollusc fauna and palynology of the lake sediments are assessed. Gastropods (Viviparidae, Stenothyridae), bivalves (Unionidae), ostracods and fish have successfully radiated in Lake Nanning, and developed a variety of endemic species. Shell thickening, spines, carinae, nodes and restricted apertures in bivalves and gastropods are interpreted as armour to prevent predation by giant shell crushing carp. Four different, successive macro-mollusc associations are documented, and can likely be used for relative dating of the lake sediments. Palynomorph assemblages from different lake stages are dominated by cool temperate conifer pollen and freshwater algae. The new findings suggest that the sediments of the Yongning Formation were deposited during or after Eocene–Oligocene cooling and are Oligocene in age. This also supports the biostratigraphy based on rare mammal finds. The fossils of Lake Nanning are outstandingly well preserved and provide a great opportunity to study endemic lake radiations. Besides, the lake sediments are one of the most important Oligocene climate archives of the region.

Description: Publication date: 15 September 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 505 Author(s): Hui Sun, Xiaodong Liu Although some studies have shown that the uplift of the northern Tibetan Plateau (NTP) has an important influence on the climate of inland Asia, the respective roles played by different parts of the NTP in controlling regional aridification and dust cycling remains unclear. In this study, based on the geological facts that the NTP and its surrounding mountains have uplifted to a certain altitude since the Miocene, we used the dust-coupled regional climate model RegCM4.1 to explore the different impacts of the uplift of four mountain ranges (the Altai Mountains–Mongolian Plateau, the Tian Shan Mountains, the Pamir Mountains, and the Qilian Mountains) on the arid climate and dust cycle of inland Asia. The results showed distinct contributions of these different mountain ranges. With respect to aridity, the uplift of the Pamirs played a leading role in the aridification of inland Asia, causing the annual mean precipitation to decrease by 200% across a wide area of Northwest China owing to the “rain shadow” effect (a rain shadow is a dry area on the leeward side of a mountainous area). In terms of dust cycling, dust emissions and deposition increased in the Taklimakan Desert mainly due to the uplift of the Tian Shan Mountains and the Pamirs, the increase in magnitude of which was 10–20 times larger than that induced by the uplift of the Altai Mountains–Mongolian Plateau or Qilian Mountains. Besides, a narrow passage formed between the uplifted Altai Mountains–Mongolian Plateau and Tian Shan Mountains that accelerated the northwesterly air flow between them, thus increasing dust emissions in northern Xinjiang and the Gobi Desert. The increase in dust emissions in these two regions induced by the uplift of the Altai Mountains–Mongolian Plateau was 7–20 times greater than that induced by the uplift of the three other mountain ranges. Results also showed that the uplift of the Qilian Mountains not only controlled the dust emissions and deposition on the Loess Plateau, but also blocked the transportation of dust from Northwest China to the middle and lower reaches of the Yangtze River, leading to the dust loading being reduced by 10–20% in South China. The findings of this study improve our understanding of the influence of NTP tectonic uplift on change in the arid climate and dust cycle of inland Asia.