Beschreibung: Publication date: 15 September 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 505

Beschreibung: Publication date: 15 September 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 505 Author(s): Rathnasiri Premathilake, Chris O. Hunt Little is known of the human use of rainforest plant resources of prehistoric Sri Lanka due to the lack of preservation of organic material and the effects of various destructive taphonomic processes. Phytoliths recovered from a AMS radiocarbon and OSL dated sequence at Fahien Rock Shelter indicate interactions of anatomically modern humans with the lowland rainforests of south-western Sri Lanka from 44,952–47,854 cal. BP to 11,991–12,402 cal. BP. During this period, the Rock Shelter occupants extracted their livelihood from a number of wild plants including bananas, rice, breadfruits, durians, canarium and species of palm and bamboo. These taxa are associated with present-day disturbed lowland rainforests. Gathering and processing of plant resources by existing modern rainforest foragers cannot directly be compared with the subsistence activities of the Late Pleistocene Rock Shelter occupants.

Beschreibung: Publication date: 15 September 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 505 Author(s): Douaa Fathy, Michael Wagreich, Susanne Gier, Ramadan S.A. Mohamed, Rafat Zaki, Mohamed M. El Nady A comprehensive set of organic and inorganic geochemical proxies, clay mineralogy, and molecular fossils are presented from two biostratigraphically well-dated oil shale horizons of Egypt, within the Upper Cretaceous Duwi and Dakhla formations. The studied oil shales were deposited within intracratonic sedimentary basins in a broad northern African epeiric sea. Calcareous nannofossil biostratigraphy indicates that the oil shales range from early to late Maastrichtian in age, covering nannofossil zones UC18, UC19, and UC20. The oil shales contain smectite and kaolinite as the main clay minerals that formed by weathering of precursor basement rocks. The relative abundances of clay minerals and several geochemical proxies (e.g. C-value, CIA, Ga/Rb, Rb/Sr and Sr/Cu), along with the occurrence of warm-water nannofossil taxa, demonstrate that the Maastrichtian oil shales accumulated under a warm, arid to humid greenhouse climate during a general Maastrichtian cooling trend. This episode of oil shale deposition in Egypt coincided with the first potential imprint of the global warming, that has been recorded during early-to-late Maastrichtian times (~70.6–67.7 Ma). Elevated eolian terrigenous input was recorded within the Duwi Formation oil shales, shown by high Ti/Al, Si/Al, Zr/Al and low La/Lu ratios. The Duwi Formation environment was characterized by enhanced salinity and a stratified water column, compared to that of the Dakhla Formation, shown by elevated values of the gammacerane index, tetracyclic terpane, β‑carotene and Sr/Ba ratio. The CaCO 3 content and carbonate/siliciclastic ratio indicate that the Dakhla Formation oil shales were deposited during a relative sea-level rise in a deeper marine setting than the Duwi Formation oil shales. The data further imply a wind-driven upwelling scenario of nutrient input s that simulated primary production and increased organic matter fluxes. Thus, paleoclimate and paleoceanography had a considerable impact on organic matter enrichment.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: 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

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