Description: Publication date: 1 February 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 491

Description: Publication date: 1 February 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 491 Author(s): Kai Liu, Qinglai Feng, Jun Shen, Maliha Khan, Noah J. Planavsky The relationship between metazoan evolution and ocean-atmosphere oxygen levels has been extensively debated. Similarly, there is no consensus on the factors controlling the evolution of the marine redox landscape. The early Cambrian is a particularly critical time interval to examine, as there is a marked increase in metazoan body plan diversity and increased ecosystem complexity, but few constraints on marine redox conditions during this seminal interval. We present an assessment of early Cambrian marine redox conditions from the Luojiacun section in west Hubei Province (the upper Yangtze platform). There are low trace elements enrichments (U, Mo) in the Yanjiahe Formation followed by an abrupt increase in the overlying Shuijingtuo Formation. U-Mo systematics in the most metal-enriched samples suggest deposition under a weakly restricted offshore basin, which is consistent with previous studies. There is correlation between excess Ba (Ba xs ) and total organic carbon (TOC), suggesting a strong production control on organic matter concentration. Further, higher Ba excess in the Shuijingtuo Formation than the Yanjiahe Formation indicates dysoxic-oxic conditions in the Yanjiahe Formation is linked to lower productivity, and anoxic conditions in the Shuijingtuo Formation are linked to higher productivity. Although strong productivity controls on Proterozoic and Paleozoic marine redox conditions have been commonly invoked, we provide some of the first empirical evidence for this control on marine redox structure. More broadly, we find that excess barium coupled with redox proxies may provide useful constraints on the interplay between preservation and production controls on organic matter abundances in the Paleozoic successions.

Description: Publication date: 1 February 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 491 Author(s): ZhongJing Cheng, ChengYu Weng, JianQiu Guo, Lu Dai, ZhongZe Zhou The late-Quaternary vegetation history of a biodiversity hotspot—the Three Parallel Rivers region (TPRR)—was palynologically studied based on a series of fluvial terrace sediments along the upper Lancang valley, southwestern China. A parallel study on the modern pollen rains in the region shows that the contemporary distribution of species along elevational gradients are distinguished by characteristic pollen assemblages, providing good analogs for the reconstruction of the vegetation history. By analyzing the sediments and pollen recovered from the terraces, a brief history of the region since the late deglaciation is revealed. During the late deglaciation (11–14 ka), the pollen assemblages were particularly rich in Abies , Picea and Betula , indicating a range expansion of the alpine forest during a relatively cold time interval. Meanwhile, co-occurring pollen of Castanopsis , Myrtaceae, Caprifoliaceae, Araliacae, Anarcadiaceae, etc. suggests these tropical/subtropical trees, which are distributed in today's evergreen forests to the south of this region, once extended into these valleys under a wetter climate. However, since the mid-Holocene, the evergreen tropical/subtropical forests have given way to savanna, as revealed from the corresponding pollen assemblages of the second terrace (4–7 ka). The alpine vegetation might have simultaneously contracted to higher elevations under a warmer climate, and subsequently retreated to its present distribution in response to the late-Holocene cooling. Our first glimpse into the Quaternary vegetation history of the TPRR provides new insights into the mountainous biotic response to climatic forcing, and therefore has important implications for diversification in these steep gorges.

Description: Publication date: 1 February 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 491 Author(s): Daniel R. Muhs, Jeffrey S. Pigati, R. Randall Schumann, Gary L. Skipp, Naomi Porat, Stephen B. DeVogel Along most of the Pacific Coast of North America, sand dunes are dominantly silicate-rich. On the California Channel Islands, however, dunes are carbonate-rich, due to high productivity offshore and a lack of dilution by silicate minerals. Older sands on the Channel Islands contain enough carbonate to be cemented into aeolianite. Several generations of carbonate aeolianites are present on the California Channel Islands and represent the northernmost Quaternary coastal aeolianites on the Pacific Coast of North America. The oldest aeolianites on the islands may date to the early Pleistocene and thus far have only been found on Santa Cruz Island. Aeolianites with well-developed soils are found on both San Miguel Island and Santa Rosa Island and likely date to the middle Pleistocene. The youngest and best-dated aeolianites are located on San Miguel Island and Santa Rosa Island. These sediments were deposited during the late Pleistocene following the emergence of marine terraces that date to the last interglacial complex (~ 120,000 yr to ~ 80,000 yr). Based on radiocarbon and luminescence dating, the ages of these units correspond in time with marine isotope stages [MIS] 4, 3, and 2. Sea level was significantly lower than present during all three time periods. Reconstruction of insular paleogeography indicates that large areas to the north and northwest of the islands would have been exposed at these times, providing a ready source of carbonate-rich skeletal sands. These findings differ from a previously held concept that carbonate aeolianites are dominantly an interglacial phenomenon forming during high stands of sea. In contrast, our results are consistent with the findings of other investigators of the past decade who have reported evidence of glacial-age and interstadial-age aeolianites on coastlines of Australia and South Africa. They are also consistent with observations made by Darwin regarding the origin of aeolianites on the island of St. Helena, in the South Atlantic Ocean, more than a century and a half ago.

Description: Publication date: 1 February 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 491 Author(s): Christopher Kendall, Anne Marie Høier Eriksen, Ioannis Kontopoulos, Matthew J. Collins, Gordon Turner-Walker An understanding of the structural complexity of mineralised tissues is fundamental for exploration into the field of diagenesis. Here we review aspects of current and past research on bone and tooth diagenesis using the most comprehensive collection of literature on diagenesis to date. Environmental factors such as soil pH, soil hydrology and ambient temperature, which influence the preservation of skeletal tissues are assessed, while the different diagenetic pathways such as microbial degradation, loss of organics, mineral changes, and DNA degradation are surveyed. Fluctuating water levels in and around the bone is the most harmful for preservation and lead to rapid skeletal destruction. Diagenetic mechanisms are found to work in conjunction with each other, altering the biogenic composition of skeletal material. This illustrates that researchers must examine multiple diagenetic pathways to fully understand the post-mortem interactions of archaeological skeletal material and the burial environment.

Description: Publication date: 1 February 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 491 Author(s): Alessandro Bonfardeci, Antonio Caruso, Annachiara Bartolini, Franck Bassinot, Marie-Madeleine Blanc-Valleron Globigerinoides ruber is the dominant taxon in the North Atlantic Subtropical Gyre, nowadays limited to the north by the Azores Current. It is highly sensitive to recent and late Pleistocene Azores Front Current System variability. In this study, we analyse the distribution of five individual morphotypes of the G. ruber – G. elongatus plexus ( G. ruber s.s., G. ruber cyclostoma type, G. elongatus , G. elongatus cf.1, G. elongatus pyramidical type) and G. ruber kummerform gr. in a core (ATA13-OF-KT1) collected southwest of the Azores islands and located in a strategical position near the present-day boundary of the Subtropical Gyre/Azores Front Current System (STG/AFCS). Micropaleontological and stable isotope analyses can provide new insights on the ecological preferences of the G. ruber chromotypes and some selected morphotypes (especially the less studied G. ruber cyclostoma type). Their distribution pattern shows cyclic oscillations linked to climatic variability at orbital and millennial scales. G. elongatus clearly dominated the G. ruber - G. elongatus assemblage during the interglacials, while G. ruber cyclostoma type reached their maxima abundances during glacial periods. Furthermore, changes in the relative abundance of warm ( G. elongatus ) and cool water ( G. ruber cyclostoma type) morphotypes represent a powerful tool to track the position occupied by the Subtropical Gyre/Azores Current (STG/AC) boundary during the last 74.7 kyr.

Description: Publication date: 1 February 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 491 Author(s): José V. Roces-Díaz, Borja Jiménez-Alfaro, Milan Chytrý, Emilio R. Díaz-Varela, Pedro Álvarez-Álvarez Areas of Quaternary refugia for tree species have been mainly delineated based on fossil records and phylogeography, but niche modelling can provide useful complementary information. Here we use palaeodistribution modelling to test the main hypotheses about the distribution of Castanea sativa in the Last Glacial Maximum (LGM) and the mid-Holocene in Europe. We computed distribution models for current climatic conditions using different methods, and projected them onto three climatic scenarios for the LGM and the mid-Holocene. The projections were validated with pollen and charcoal records. LGM refugia were suggested in the north of the Iberian, Italian and Balkan Peninsulas, and in northern Anatolia. The projections for the mid-Holocene indicated high climatic suitability and geographic expansion of the species range across southern Europe, including some areas where the species is nowadays considered as non-native. In general, our models are consistent with the patterns proposed with pollen and charcoal records, and partially also with phylogeographic information inferred from genetic data, suggesting that the most suitable areas for C. sativa were extended significantly during the mid-Holocene, but declined afterwards and lost connectivity. The projected patterns were compatible with existing palaeobotanical records of C. sativa and provide a spatially-explicit picture of the species past distribution.

Description: Publication date: 1 February 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 491 Author(s): Logan A. Wiest, William E. Lukens, Daniel J. Peppe, Steven G. Driese, Jack Tubbs Recent research has demonstrated that the Lilliput effect (reduction of body size in biota associated with the aftermath of mass extinctions) affected all trophic levels in the marine realm following the Cretaceous-Paleogene (K-Pg) event. However, it is unclear if this size change was strictly a marine signal, or a global phenomenon that also affected continental ecosystems. Herein we present the results of an ichnological proxy for body size of soil-dwelling insects across the K-Pg boundary in Big Bend National Park, Texas, U.S.A. Quantitative efforts focused on Naktodemasis bowni , which are characterized as unbranching burrows composed of ellipsoidal packets of backfill menisci. These traces were likely produced by beetle larvae or cicada nymphs based on previous comparison with structures generated in modern soils and laboratory experiments. As an approximation for the body size of the subterranean insects, this dataset indicates that a smaller N. bowni diameter (D N ) is statistically correlated (α 〈 0.05) with several edaphic factors including poor soil drainage and weak soil development (Entisols). Additionally, the D N in strata immediately superjacent to the highest Cretaceous-specific taxa is smaller by 23% (5.6 ± 1.8 mm) in comparison to D N within the subjacent Cretaceous interval (7.3 ± 2.7 mm). This abrupt shift occurs in a well-drained Inceptisol, and cannot be attributed to facies changes, drainage, or paleosol maturity. Furthermore, a reduced D N (6.6 ± 2.3 mm) persists above this anomalous shift for at least 20 stratigraphic meters within chron 29r. The cause for this negative response in body size within soil-dwelling biota may be attributed to plant-community shifts in taxonomic composition and ecological strategies, which would have caused fundamental alterations to the diet of the herbivorous, subterranean insects. This study provides empirical evidence that the Lilliput effect was not restricted to marine environments during the aftermath of the K-Pg event.

Description: Publication date: 1 February 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 491 Author(s): Martin G. Lockley, Ken Cart, John Foster, Spencer G. Lucas Late Triassic and Early Jurassic tetrapod track assemblages are abundant and quite well documented from the respective Chinle and Glen Canyon groups of the Dolores Valley region of western Colorado and adjacent regions, especially eastern Utah. However, gaps still exist in our knowledge of the spatial and temporal distribution of representative ichnogenera. The stratigraphic distribution of track assemblages in the cliff-forming Wingate Sandstone Formation, the lower unit of the Glen Canyon Group, underlying the Kayenta and Navajo formations, is difficult to determine because almost all Wingate assemblages are known only from fallen blocks, originating from precipitous, vertical cliffs, which yield both dune and interdune ichnofaunas. Among the characteristic Lower Jurassic biochron ichnogenera Grallator , Eubrontes , Otozoum , Anomoepus and Batrachopus , in the Dolores Valley only Grallator is known abundantly, while Otozoum , and Batrachopus were previously known only from single occurrences, and Eubrontes and Anomoepus have yet to be reported. We here report two large, Batrachopus -rich assemblages that give new insight into the interdune paleoenvironments frequented by the Batrachopus trackmaker, traditionally regarded as a basal crocdylomorph, and the theropodan trackmaker of Grallator . Both assemblages contain the best-preserved and most abundant Batrachopus currently known, locally in high densities. Where individual trackways are clearly visible they indicate that the trackmakers had variable gaits. A third new assemblage containing Batrachopus from Salt Creek is also described, as is a fourth new assemblage from the Uncompahgre Plateau which yields moderately large theropod tracks (cf. Eubrontes ), but no Batrachopus . Although diagnostic Late Triassic biochron ichnogenera like Brachychirotherium occur in basal units of the Wingate Sandstone, Batrachopus which is considered an Early Jurassic biochron ichnotaxon, occurs within the formation. Thus, vertebrate ichnotaxa help place the Triassic–Jurassic boundary within the Wingate Formation, shed light on their spatio-temporal distribution, and underscore their utility for paleoecological interpretation, in a unit devoid of tetrapod body fossils.

Description: Publication date: 1 February 2018 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 491 Author(s): Aram Bayet-Goll, Carlos Neto de Carvalho, Mehdi Daraei, Paolo Monaco, Mahmoud Sharafi This study analyzes in detail the beds bearing Rhizocorallium in the Upper Triassic Nayband Formation (Tabas Block, Central Iran) and shows their potential in interpreting depositional settings, ecological features and sequence stratigraphy. An integrated approach combining ichnological, sedimentological and stratigraphic methods has significantly enhanced our understanding of the changes in the spatial distribution style and morphological differences among the same ichnospecies of Rhizocorallium . The Upper Triassic Rhizocorallium assemblages from the Nayband Formation reveal significant spatial variations in the orientation and dimensions (i.e., length, width, limb diameter), the tiering pattern, and the colonization style throughout systems tracts and at erosional discontinuities or omission surfaces. Based on the wide variety of forms and orientation, numerous morphotypes of Rhizocorallium are grouped into two main types, i.e., those that are mostly facies controlled and those that appear abundantly in a confined stratigraphic interval and are facies independent. In this respect, three paleoichnocoenoses or habitats for the rhizocorallid producers could be differentiated according to the burrow morphology and the nature and consistency of the substrate: (1) stable habitat, represented by soft substrates including horizontal, long, straight or slightly sinuous, spreite-bearing, U-shaped protrusive burrows of Rhizocorallium irregulare (= R. commune var. irregulare ). This habitat resulted from processes operating in settings that are characterized by soft substrates, reduced sedimentation rates, and abundant food supply, typical of low- to moderate-energy, fully marine conditions; (2) unstable, physically-controlled habitat, represented by a suite of shifting substrates with low- to high-energy settings, including short, U-shaped protrusive spreiten-burrows of R. jenense (Type 1) . In this habitat alternating and contrasting energy conditions did exist due to repeated storm events that were the main controlling factor in the distribution and preservation of Rhizocorallium ; (3) substrate-controlled habitat represented by a suite of stiff-to-firm substrates including oblique to vertical protrusive or retrusive spreiten U-shaped burrows of R. jenense (Type 2) . The erosional discontinuities or omission surfaces related to this habitat include parasequence-bounding transgressive surfaces of erosion (TSE) and parasequence-bounding flooding surfaces (FS) and are mainly associated with the Rhizocorallium -dominated Glossifungites ichnofacies. Complementary ichnological information indicates that the shift in the orientation and the morphological features of rhizocorallid burrows point to broad changes of environmental parameters, which are, in turn, controlled by the rate of sea-level changes.