Palaeoenvironmental Information Research Articles

A luminescence-derived cryptostratigraphy from the Lake Suigetsu sedimentary profile, Japan: 45,000–30,200 IntCal20 yr BP

The luminescence characteristics of sediments are affected by a variety of environmental factors, reflecting both local and broader regional influences. If seeking to apply stimulated luminescence as a ‘pure’ dating technique, variability in these external variables needs to be controlled for, involving, inter alia, lengthy pretreatment procedures and complex dose rate corrections. However, in so doing, a lot of potentially valuable palaeoenvironmental information is lost.Instead, in the present study, we explicitly analysed raw, non-pretreated sediment that preserves this wealth of contributory environmental influence. Using a SUERC portable luminescence (POSL) reader, we performed rapid profiling across a 14,800 year interval of the annually laminated (varved) Lake Suigetsu sedimentary profile, central Japan (i.e., 45,000 to 30,200 IntCal20 yr BP), producing 303 contiguous measurements with a mean sampling resolution of 49 years. To further inform our understanding of this dataset, additional follow-up laboratory dosing was performed to provide sensitivity estimates.The ‘cryptostratigraphy’ (‘hidden stratigraphy’) revealed by our data includes the identification of a step-change in luminescence parameters circa 39,200 IntCal20 yr BP, which we attribute to a major earthquake that resulted in re-routing of inflow to the lake. Further variability in the derived luminescence signals is compared with supporting high resolution x-ray fluorescence (μXRF) data and palynological data from Lake Suigetsu. A correlation between the luminescence profile (both net infra-red-stimulated and net blue light-stimulated signals) and mean annual temperature is revealed, mediated through subtle differences in sediment characteristics under warmer or cooler climatic conditions.

Extensive carbon cycle between peatland and vegetation: Insights from high net primary productivity of the Middle Jurassic in northwestern China

Peatlands have obvious carbon storage capacity and are crucial in mitigating global climate change. As the end-product of peatlands, coals have preserved a large amount of palaeoenvironmental information. The carbon accumulation rate and the net primary productivity (NPP) of coal-forming peatlands can be used as proxies for recovering palaeoenvironments. A super-thick coal seam (42°35′N, 91°25′E) was developed in the Middle Jurassic Xishanyao Formation in the Shaerhu coalfield in the southern margin of the Tuha (Turpan-Hami) Basin, northwestern China. In this study, we use the time series analysis to identify the periods of Milankovitch orbital cycles in the Gamma-ray curve of this super-thick (124.85 m) coal and then use the obtained cycle periods of 405 ka, 173 ka, 44 ka, 37.6 ka, 22.5 ka to calculate the timeframe of the coal-forming peatlands which ranges from 2703.44 to 2975.11 ka. Considering that the carbon content of the coal seam is 78.32% and the carbon loss during the coalification is about 25.80%, the carbon accumulation rate of the targeted coal seam is estimated to be 58.47–64.34 g C/m2·a, and the NPP is estimated to be 252.28–277.63 g C/m2·a. The main palaeoenvironmental factors controlling the NPP of peatlands are CO2 content, palaeolatitude and palaeotemperature. The reduced NPP values of the palaeo-peatlands in the Shaerhu coalfield can be attributed to the mid-palaeolatitude and/or too low atmospheric CO2 contents. To a certain extent, the NPP of palaeo-peatlands reflects the changes in atmospheric CO2, which can further reveal the dynamic response of the global carbon cycle to climate change. Therefore, predicting the level of NPP in the Middle Jurassic and studying the final destination of carbon in the ecosystem are beneficial to understanding the coal-forming process and palaeoenvironment.

Elucidating the morphology and ecology of Eoandromeda octobrachiata from the Ediacaran of South Australia

AbstractEoandromeda octobrachiata is a poorly understood Ediacaran organism, with spiral octoradial arms, found in South Australia and South China. The informal Nilpena member of the Rawnsley Quartzite, Flinders Ranges in South Australia preserves more than 200 specimens of Eoandromeda. Here we use the novel application of rotational geometric morphometrics together with palaeoenvironmental information to provide a better insight into their palaeobiology and ecology, and to address conflicting hypotheses regarding mode of life and taxonomic affinity. We find that Eoandromeda probably had a radially symmetrical shape in life, was cone shaped and had a high relief off the microbial mat. Analysis of the symmetric and asymmetric shape components showed that they deform strongly in the direction of palaeocurrent, therefore they are thought to be made of a flexible material. Almost all specimens are compressed flat. Specimens that appear to have not fully collapsed support the idea that Eoandromeda was probably cone shaped and suggest that they possibly collapsed spirally. Our shape analysis, along with observed morphological features, support a benthic rather than pelagic mode of life. Morphological and ecological inconsistencies do not fully support the hypothesis of a Ctenophora taxonomic affinity.

Palaeoenvironmental support for long-term aquatic refugia in Australia’s Great Artesian Basin discharge springs

ABSTRACT In dryland areas, wetland refugia that provide permanent wetted habitats are important for the persistence of obligate aquatic species. Situated in Australia’s arid and semiarid regions, Great Artesian Basin discharge springs contain high biodiversity and many endemic species and are believed to provide the only permanent wetted habitat. However, conflicting information indicates that hydroperiods in these springs can be variable. The aim of this study was to use palaeoenvironmental information to assess millennial-scale variability in one large spring wetland and provide an initial assessment on the long-term presence of wetted habitat. A sediment core was collected from Big Spring at Byarri (Edgbaston Station) in central Queensland, Australia, and the sedimentary layers were analysed using radiocarbon dating, geochemistry, and palynology. An age model developed on the radiocarbon dates indicated that changes in the rate of sediment deposition are likely associated with the last glacial maximum but with no disruption in the sediment accumulation, or therefore wetland development. Variable wetland and landscape conditions over ∼43 000 years are supported by the geochemistry and palynological sedimentary records, including a change from a lacustrine to palustrine wetland and more recent changes, likely due to an anthropogenic presence in the landscape. The lack of a hiatus in available wetted habitat throughout the period of sediment development corroborates that Great Artesian Basin discharge springs represent a permanent wetted refugia in Australia’s drylands.

Living in an ecotone: Late Middle Palaeolithic occupations in the lower Besor Basin, north-western Negev Desert, Israel

The north-western Negev is an under-researched ecotonal region. We excavated two late Middle Palaeolithic open-air sites and recovered rich lithic industries that could be refitted, as well as remains of fauna, and charcoal. Palaeoenvironmental information and dates indicate interesting inter-site differences.

Sea ice and productivity changes over the last glacial cycle in the Adélie Land region, East Antarctica, based on diatom assemblage variability

Abstract. Although diatoms can provide important palaeoenvironmental information about seasonal sea ice extent productivity, sea surface temperature, and ocean circulation variability, there are still relatively few studies analysing the last glacial cycle near the Antarctic continent. This study examines diatom assemblages over the last glacial cycle from core TAN1302-44, offshore Adélie Land, East Antarctica. Two distinct diatom assemblages were identified using principal component analysis (PC 1–PC 2). The PC 1 assemblage is characterised by Thalassiosira lentiginosa, Actinocyclus actinochilus, Eucampia antarctica, Azpeitia tabularis and Asteromphalus hyalinus and is associated with the interglacial, sedimentary Facies 1, suggesting that the MIS 5e and Holocene interglacials were characterised by seasonal sea ice environments with similar ocean temperature and circulation. The PC 2 assemblage is characterised by Fragilariopsis obliquecostata, Asteromphalus parvulus and Thalassiosira tumida and is associated with the glacial Facies 2. The variability of PC 2 indicates that, during the MIS 4–2 glacial and the last glaciation, there was an increase in the length of the sea ice season compared with that of the interglacial period, yet there was still no permanent sea ice cover. The initial increase of PC 2 at the start of the glaciation stage and then the gradual increase throughout late MIS 4–2 suggest that sea ice cover steadily increased, reaching a maximum towards the end of MIS 2. The increase in sea ice during glaciation and MIS 4–2 glacial is further supported by the increase in the Eucampia index (terminal/intercalary valve ratio), an additional proxy for sea ice, which coincides with increases in PC 2. Aside from the statistical results, the increase in the relative abundance of Thalassiothrix antarctica at 40 and 270 cm suggests that, during the last two deglacials, there was a period of enhanced nutrient delivery, which is inferred to reflect an increase in upwelling of Circumpolar Deep Water. Interestingly, the diatom data suggest that, during the last deglacial, the onset of increased Circumpolar Deep Water occurred after the loss of a prolonged sea ice season (decrease in PC 2) but before the ice sheet started to retreat (increase in IRD). Together, these results suggest the changes in sea ice season potentially influenced the ocean's thermohaline circulation and were important factors in driving the climate transitions. The results contribute to our understanding of the sea ice extent and ocean circulation changes proximal to East Antarctica over the last glacial cycle.

The end of Late Glacial in north-eastern Iberia: the small mammal assemblage from Cudó cave (Mont-Ral, Tarragona)

ABSTRACTOne of the markers of the Late Pleistocene is highly fluctuating climatic conditions, with the Last Glacial Maximum (LGM, 26.5–19 ka cal before present (BP)) known to be one of the coldest periods. This work explores how the environment of north-eastern Iberia changed in relation to global climatic changes experienced during the Late Pleistocene, specifically around the LGM. Small mammal assemblages from Cudó cave (Tarragona, Spain) were used considering their well-known reliability for palaeoenvironmental reconstructions. Based on the taxonomic identification and the taphonomic analysis, several methodologies covering both qualitative and quantitative approaches were used to obtain the palaeoenvironmental information corresponding to level 107 and level 105 of Cudó cave (31.2–24.4 and 15.5–10.2 ka cal BP, respectively). The taphonomic results obtained point out owls (category 3) as the main accumulator of the small mammals. The palaeoenvironmental reconstruction shows that both levels experienced colder (−7.2oC/–4.4 °C) and wetter (+848 mm/ + 586 mm) climatic conditions than nowadays. However, in level 107 the environment was dominated by mid-European species and rocky landscape, while in level 105 it was dominated by Mediterranean species and woodland habitat. These conditions are consistent with the trend in north-eastern Iberia following several climatic events before and after the LGM coinciding with the period of Cudó cave assemblages.

Preservation of biotic and palaeoenvironmental signatures in organosulfur compounds of immature fine-grained sedimentary rocks

Organosulfur compounds (OSCs) in sedimentary rocks are considered to have formed primarily by abiotic incorporation of inorganic sulfur species into biogenetic functionalized molecules during early diagenesis, thus preserving carbon skeletons of appropriate biomolecules. OSCs could be characterized at a molecular level by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) even when they are small in amounts and large in molecular weights. Herein, to reveal the palaeoecological and palaeoenvironmental information that OSCs have recorded but might not be contained in other biomarkers, OSCs’ composition in solvent extracts of rocks with different geological histories were determined utilizing FT-ICR-MS. The analyzed natural laboratories are the marine Schöneck, Dynow and Posidonia formations and the lacustrine Wealden Formation which are in the late diagenetic or early catagenetic stages.The prevailing iron-deficient sulfidic depositional settings of the marine Posidonia and Schöneck formations are reflected by abundant OSCs bearing up to three sulfur atoms. The high ratios of reduced relative to oxidized forms (Sz versus SzOx) further illustrate the restricted presence of oxidants at the oxic-anoxic interfaces. The high average oxygen numbers of S1Ox compounds and the exclusive presence of nitrogenous OSCs (SzNy and SzNyOx) found in the marine rock extracts document the high abundances of polyoxygenated compounds and proteinaceous moieties in marine organisms that can be sulfurized. In contrast, the lacustrine organisms contain abundant sulfurizable aliphatic moieties.The observed prominent enrichment of Sz and SzOx compounds containing 40, 35, 30, 25 carbon atoms are associated with the selective and efficient preservation of polyfunctionalized biomolecules via sulfurization, such as C40 carotenoids, C35 bacteriohopanepolyols, C30 unsaturated tetracyclic polyprenoid alcohols, or C25 or C30 highly branched isoprenoid (HBI) polyenes. The strong enrichment of sulfurized C35 bacteriohopanepolyols can be developed as an indicator of the low levels of oxygen exposure prior to sulfurization, which occur only in the Dynow and Schöneck formations. The prominent enrichment of sulfurized carotenoids is generally associated with high primary productivity. While the strongly enriched sulfurized HBI polyenes in the Upper Schöneck Formation is indicative for diatom blooms, the precursors of C30 pentacyclic polyprenoid organosulfur compounds are more abundant in fresh/brackish water algae.

Origin and characteristics of ancient organic matter from a high‐elevation Lateglacial Alpine Nunatak (NW Italy)

AbstractIn high‐mountain areas, Pleistocene glaciations and erosion‐related processes erased most of the pre‐existing landforms and soils. However, on scattered stable surfaces, ancient soils can be locally preserved for long periods, retaining valuable palaeoenvironmental information. Such relict surfaces survived during glaciations either through coverage by non‐erosive, cold‐based, ice or as nunataks. Thus, soils preserved on such surfaces retain an excellent pedo‐signature of different specific past climatic/environmental conditions. In this study, we performed a detailed chemical characterisation of the organic material found in palaeosols, discovered inside periglacial features on a high‐elevation Lateglacial Alpine Nunatak (Stolenberg Plateau), above 3000 m a.s.l. (NW Italian Alps). The soil organic matter (OM) was separated into different pools by means of density fractionation, in order to separate the more fresh/unaltered free and occluded organic material (Light Fraction) from the stable fraction chemically bound to the mineral phase (Mineral Organic Matter—MOM). To better characterise the MOM fraction, this was further subjected to chemical fractionation, in order to separate the alkali‐extractable OM (ext‐MOM) from the fraction intimately bound to minerals. The obtained fractions were then characterised by chemical and 13C nuclear magnetic resonance (NMR), and Fourier Transform Infrared (FT‐IR) spectroscopy. The results indicated that the largest part (>90%) of organic carbon was stored in the stable MOM pool, characterised by a high degree of decomposition and consisting mainly of paraffinic substances, such as lipids and waxes (37–50%), cellulose and hemicellulose (29–37%). The OM likely originated from autochthonous, well‐adapted, ancient alpine vegetation (alpine tundra) that grew on the Plateau during warm climatic phases since the end of the Last Glacial Maximum (LGM). These results further strengthen the palaeoenvironmental reconstruction at the Stolenberg Plateau, which represents a Lateglacial Alpine Nunatak, and has acted as biological refugia (at least) since the end of the LGM.Highlights The origin and composition of ancient organic matter from a high‐elevation Alpine Nunatak were uncovered. More than 90% of organic carbon was stored in the stable mineral organic matter (MOM) pool. Based on NMR and FT‐IR spectra the MOM fraction consisted of paraffinic substances (37–50%), cellulose and hemicellulose (29–37%). The organic matter originated from ancient alpine tundra that developed on the Nunatak since the end of the Last Glacial Maximum.

Environmental changes in Sorbas arid region (Southern Spain) during MIS 5a inferred from a carbonate flowstone from a gypsum cave

Present climate conditions impede the formation of calcite speleothems in the gypsum caves of the semi-arid region of Sorbas (Southern Spain). However, U-Th dating reveals the uninterrupted deposition of a 46 mm-thick carbonate flowstone in the Sorbas caves from ∼78 to ∼71 ka, during Marine Isotope Stage (MIS) 5a. This indicates that the area was vegetated during this period, producing biogenic CO2 in soils necessary for the underground deposition of the speleothem, which contrasts with the current unvegetated landscape. During MIS 5a, rainfall recharged the karst aquifer, leading to cave seepage. The development of soils and persistent water infiltration suggests a higher precipitation/evapotranspiration ratio with respect to the present, which was likely favored by lower regional temperatures and a different annual rainfall regime. δ18O and δ13C analyses testify that the speleothem recorded climate pulses synchronous, and structurally similar, with Greenland interstadial and stadial periods, with relatively wetter conditions recorded during interstadials 21.1, 20 and 19.2, and drier periods during stadials 21.1 and 20. This demonstrates that the climate in the desert-like environment of Sorbas is sensitive to inter- and intra- hemispherical triggers, such as the extent of Northern ice sheets and the Atlantic meridional overturning circulation. Interstadials (stadials) were also characterized by a higher (lower) Atlantic/Mediterranean moisture source ratio. For the first time, we show that carbonate speleothems formed in arid gypsum caves can record reliable palaeoenvironmental information spanning multiple millennia, procuring proxies for detailed palaeoclimate reconstructions. Such speleothems are thus excellent candidates for understanding past climate dynamics and patterns in desert-like gypsum terrains.

Spatio-Temporal Variations in the Geochemistry of Laguna Salada de Chiprana, NE Spain

Hypersaline lakes are sensitive and increasingly threatened ecological and depositional environments that are host to a diverse spectrum of industrial services, natural resources, and environmental processes. Furthermore, they are also important repositories of high-resolution palaeoenvironmental information and are potentially key archives in the reconstruction of environmental, climatic conditions and past human impacts in areas where other such repositories may not be available. Many saline lakes are threatened by increased farming and irrigation practices and the effects of global warming. Geochemical XRF analyses of a transect of sediment cores from Laguna Salada de Chiprana, a permanent hypersaline lake in the Iberian Peninsula, provide insights into geochemical processes and palaeoenvironmental changes occurring at the site throughout the last 300–400 years. Key changes identified within the sequence are defined both from a spatial and temporal aspect and characterise the profundal and littoral sub-environments of the lake. Initially, the onset of a phase of widespread agriculture and irrigation in the region occurred in the late 16–17th century to ~1850AD and was associated with relative increases in lake levels. This was followed by decreasing lake levels between 1850 and 1950AD, likely associated with increasing evaporative processes and decreased irrigation returns to the lake, which also allowed for increased organic productivity in the profundal setting. This may have been associated with the transition of the site to a wetland-type setting, where biological processes were able to flourish in the shallower central depocentres of the lake. In sequence, the introduction of farm machinery and changing irrigation patterns occurred around 1950, causing small increases in lake levels, colonization by charophytes as well as increased organic productivity in the littoral setting, likely due to the establishment of suitable environments for biological processes to occur in the shallower margins of the lake when water levels rose. From this period to the present day, slow drawdown of the lake has occurred coupled with increasing management of the site by the regional government, leading to several phenomena. Evaporative processes are high throughout the lake; there are falling but highly variable water levels and there is a segmentation of organic productivity, whereby falling lake levels permit increased organic productivity in the profundal setting but decrease productivity in the littoral setting due to the establishment of harsh evaporitic and erosive conditions in this area. The reconstruction reveals the high sensitivity of Lake Chiprana as an environmental archive and illustrates the need to utilise multiple sediment cores for accurate palaeoenvironmental reconstructions of saline lakes due to the strong variability in depositional and geochemical sub-environments.

Molecular biomarkers in Batagay megaslump permafrost deposits reveal clear differences in organic matter preservation between glacial and interglacial periods

Abstract. The Batagay megaslump, a permafrost thaw feature in north-eastern Siberia, provides access to ancient permafrost up to ∼650 kyr old. We aimed to assess the permafrost-locked organic matter (OM) quality and to deduce palaeo-environmental information on glacial–interglacial timescales. We sampled five stratigraphic units exposed on the 55 m high slump headwall and analysed lipid biomarkers (alkanes, fatty acids and alcohols). Our findings revealed similar biogeochemical signatures for the glacial periods: the lower ice complex (Marine Isotope Stage (MIS) 16 or earlier), the lower sand unit (sometime between MIS 16–6) and the upper ice complex (MIS 4–2). The OM in these units has a terrestrial character, and microbial activity was likely limited. Contrarily, the n-alkane and fatty acid distributions differed for the units from interglacial periods: the woody layer (MIS 5), separating the lower sand unit and the upper ice complex, and the Holocene cover (MIS 1), on top of the upper ice complex. The woody layer, marking a permafrost degradation disconformity, contained markers of terrestrial origin (sterols) and high microbial decomposition (iso- and anteiso-fatty acids). In the Holocene cover, biomarkers pointed to wet depositional conditions and we identified branched and cyclic alkanes, which are likely of microbial origin. Higher OM decomposition characterised the interglacial periods. As climate warming will continue permafrost degradation in the Batagay megaslump and in other areas, large amounts of deeply buried ancient OM with variable composition and degradability are mobilised, likely significantly enhancing greenhouse gas emissions from permafrost regions.

Facies variability and depositional settings of Laguna Salada de Chiprana, an Iberian hypersaline lake

AbstractHypersaline lakes are unique depositional environments that are highly sensitive to climatic changes and anthropogenic pressures. Strong physicochemical gradients and the interplay of physical, chemical and biological depositional processes coupled to variable preservation potential associated with these environments generate highly complex sedimentary sequences. This study aimed to investigate spatio‐temporal variations throughout the last three centuries in the sedimentary sequence of Laguna Salada de Chiprana, a small, permanent hypersaline lake situated in Northeast Spain. Short sediment cores reveal a complex sedimentary sequence influenced by detrital, chemically‐induced and biogenically‐influenced depositional processes. Nine facies associated with six sedimentological units represent six periods of environmental change beginning from approximately pre‐1800 ad to the present day. They include: (i) a shallow, permanent saline lake that experienced brief periods of anoxia and drawdown between pre‐1800 ad and ca 1850 ad. This was succeeded by: (ii) increased lake levels and detrital input to the lake from ca 1850 to 1900 ad; and (iii) a fall in lake levels and the establishment of microbial mats within bottom waters fluctuating between oxic and anoxic conditions from ca 1900 to 1950 ad. (iv) From ca 1950/1960 ad, a minor increase in lake levels and colonization of the littoral and sub‐littoral zones by macrophytic vegetation occurred; followed by (v) falling lake levels and increasing salinity between 1960 and 1970 ad leading to widespread encrustation of macrophytes in the littoral zones by carbonate–evaporite precipitates. Finally (vi), from ca 1970 ad to the present day, falling lake levels, elevated salinity and widespread colonization of the lake by microbial mats characterize the sedimentary environment. Climate reconstructions and documentary evidence indicate that depositional evolution was mostly controlled by changes in farming practices and irrigation policies. Understanding Laguna Salada de Chiprana’s depositional evolution contributes to future definitions of high‐resolution palaeoenvironmental models, not only within the Iberian Peninsula but also in other locations where saline–hypersaline lakes act as a key source of palaeoenvironmental information.

Contrasting intensity of aragonite dissolution and dolomite cementation in glacial versus interglacial intervals of a subtropical carbonate succession

AbstractAragonite and high‐Mg calcite are abundant in modern, neritic carbonate systems but almost absent in their fossil counterparts. Dissolution of these metastable mineral phases commonly leaves no visible trace in the sedimentary record, compromising the derivation of palaeoenvironmental information from the rock record. The upper 25 m of Integrated Ocean Drilling Program (IODP) Site U1460 on the outer ramp of the western Australian Shelf were investigated to study shallow burial (tens of metres) marine diagenesis in organic‐carbon poor sediments using microscopic, total organic carbon, biomarkers and mineralogical analysis in combination with porewater geochemistry. Aragonite dissolution is negligible at the seafloor but intensifies ca 5 m below, even though bulk porewaters are supersaturated for aragonite. This apparent contradiction likely results from dissolution in undersaturated microenvironments. Aragonite dissolution below 5 to 6 m is on average more intense in interglacial compared to glacial intervals. The presence of disseminated framboidal pyrite and porewater results indicate that minor sulphate reduction is active at IODP Site U1460. Sulphate reduction is probably limited by the low organic matter content (ca 0.2%). It is well‐known from the literature that incipient sulphate reduction can lead to a drop in pH and consequently to carbonate dissolution. It is therefore assumed that the slightly higher concentration of organic matter in the interglacial intervals allowed increased aragonite dissolution during sulphate reduction compared to glacial beds. Low amounts of dolomite cement (<15%) start to form at the same depth (5 to 6 m) as aragonite dissolution intensifies. Dolomite formation and aragonite dissolution also show covariance on a metre‐scale below 5 to 6 m, indicating that a low carbonate saturation state might enhance dolomite formation. This mechanism provides an indirect link between dolomite formation, aragonite dissolution and orbital cycles. The outcome of this study, therefore, contributes to a better understanding of differential diagenesis in marine carbonates.

Preservation of aragonite in Late Cretaceous (Campanian) turtle eggshell

Among amniotes, turtles are the only clade that lay aragonitic eggs. Because aragonite is a metastable mineral, unequivocal preservation of aragonite in fossil turtle eggs has only been reported from Pliocene deposits. Here, we report in situ preservation of aragonite in a turtle egg from the Judith River Formation (Campanian) of Montana, USA. We utilized electron backscatter diffraction (EBSD) and Raman spectroscopy to explore the carbonate mineral polymorphs in the eggshell. The EBSD maps show the presence of both aragonite and calcite with the former preserved as needle-like crystal, a feature of all turtle eggshells. The presence of aragonite is independently validated by Raman maps. This dual approach provides direct, unambiguous evidence that the record of aragonitic turtle eggshell dates back at least to the Campanian (ca. 76 Ma) and supports the hypothesis that aragonitic eggshell is a synapomorphy of all turtles. The presence of pristine aragonite also indicates minimal taphonomic alteration at the fossil locality. Consequently, diverse invertebrate or vertebrate fossils from localities with aragonitic turtle eggs may provide high quality, unaltered palaeoenvironmental information. • A Late Cretaceous turtle egg preserves aragonite. • EBSD and Raman spectroscopy provide independent approach. • It supports the view that aragonitic egg is synapomorphic to all Testudinata. • Judith River Formation and its equivalent strata may preserve more aragonitic fossils.

New remains of Nalamaeryx (Tragulidae, Mammalia) from the Ladakh Himalaya and their phylogenetical and palaeoenvironmental implications

ABSTRACT Nalameryx savagei is one of the rare mammals found in India during the Oligocene. Five dental remains composed the originally found material, described in 1990. The first phylogenetic hypothesis proposed Nalameryx to be closely related to the basal ruminant Lophiomerycidae. The description of new specimens from the type bed K/7b from the Kargil Formation (late Oligocene, India), led to a reinterpretation of the phylogenetic position of Nalameryx and of the early evolutionary history of the Tragulidae. Based on our phylogenetic hypothesis, Nalameryx is nested within the living Tragulidae, making it one of the oldest known tragulid. Moreover, the enigmatic late Eocene Stenomeryx from Myanmar is not recovered as a ruminant in our analysis. Tooth isotopic data indicate that Nalameryx fed on plants that have grown under xeric conditions. This is in agreement with palaeoenvironmental information observed on plants from Turkish and Pakistani localities where Nalameryx has already been found. This region of the world had a seasonal climate with an arid period during the late Oligocene.

High-resolution geophysical imaging of reptile burrows (San Salvador rock iguana, the Bahamas): implications for ichnology and conservation ecology

Abstract Neoichnological research of terrestrial tracemakers in coastal settings provides important palaeoenvironmental information about their context within the subaerial facies. Here we present the first geophysical dataset of reptile burrows in a carbonate substrate and use it to help visualize parts of the burrows of the Bahamian (San Salvador) rock iguana ( Cyclura rileyi ). High-resolution 800 MHz ground-penetrating radar (GPR) images within an enclosure on San Salvador Island were employed to discriminate between the electromagnetic signal response from subsurface anomalies related to air-dominated voids or live animals within burrows. The dielectric contrast between the carbonate substrate and open burrows was sufficient to identify the majority of the 15–20 cm-wide subsurface extensions of the inclined tunnels in the upper 30–40 cm. Whereas limestone clasts induced some interference, it is possible to differentiate their high-amplitude diffractions from those produced by the iguana burrows. Our research indicates that GPR imaging is a viable, rapid, non-invasive method of visualizing animal burrows, with implications for neoichnology, palaeoichnology, and conservation ecology of semi-fossorial species. Furthermore, the critically endangered status of Bahamian land iguanas, as well as ongoing threats from natural and introduced pressures, highlights the need for research into their ichnological record.

Marine and marginal marine Ostracoda as proxies in geoarchaeology

Ostracoda, minute aquatic crustaceans with calcitic shells, are highly versatile proxies in geoarchaeological contexts. Their species-specific ecological preferences and ranges allow the reconstruction of palaeoenvironments and anthropogenic impacts in detail. Environmentally driven morphological variability and shell chemistry signatures as stable isotope and trace element values can provide additional palaeoenvironmental information. Ostracods can be used for provenance analyses and stratigraphical investigations as well. Their small size and high abundance in most water bodies makes them ideal for studying sediment cores and smaller samples from trenches or outcrops, especially in coastal areas where they show a high diversity and abundance compared to other groups of meiofauna. In archaeological contexts, fossil ostracods may provide information about climate, sea level and hydrography, high energy events like storms or tsunamis, ocean currents, land use, pollution, water constructions, stratigraphy, trade connections or the origin of sediment material.We give an overview on the state of ostracod-based research in geoarchaeology today and present some European case studies to illustrate concepts and methods of such field of study.

True substrates: The exceptional resolution and unexceptional preservation of deep time snapshots on bedding surfaces

AbstractRock outcrops of the sedimentary–stratigraphic record often reveal bedding planes that can be considered to be true substrates: preserved surfaces that demonstrably existed at the sediment–water or sediment–air interface at the time of deposition. These surfaces have high value as repositories of palaeoenvironmental information, revealing fossilized snapshots of microscale topography from deep time. Some true substrates are notable for their sedimentary, palaeontological and ichnological signatures that provide windows into key intervals of Earth history, but countless others occur routinely throughout the sedimentary–stratigraphic record. They frequently reveal patterns that are strikingly familiar from modern sedimentary environments, such as ripple marks, animal trackways, raindrop impressions or mudcracks: all phenomena that are apparently ephemeral in modern settings, and which form on recognizably human timescales. This paper sets out to explain why these short‐term, transient, small‐scale features are counter‐intuitively abundant within a 3.8 billion year‐long sedimentary–stratigraphic record that is known to be inherently time‐incomplete. True substrates are fundamentally related to a state of stasis in ancient sedimentation systems, and distinguishable from other types of bedding surfaces that formed from a dominance of states of deposition or erosion. Stasis is shown to play a key role in both their formation and preservation, rendering them faithful and valuable archives of palaeoenvironmental and temporal information. Further, the intersection between the time–length scale of their formative processes and outcrop expressions can be used to explain why they are so frequently encountered in outcrop investigations. Explaining true substrates as inevitable and unexceptional by‐products of the accrual of the sedimentary–stratigraphic record should shift perspectives on what can be understood about Earth history from field studies of the sedimentary–stratigraphic record. They should be recognized as providing high‐definition information about the mundane day to day operation of ancient environments, and critically assuage the argument that the incomplete sedimentary–stratigraphic record is unrepresentative of the geological past.

Fossil woods from the Olenekian (late Early Triassic) Shaofanggou Formation in the Junggar Basin, Northern Xinjiang, North‐west China

A large number of fossil woods were preserved in the Permian–Triassic sequences in the Junggar Basin of Xinjiang Uygur Autonomous Region. These wood fossils provide a lot of palaeoenvironmental information of the Junggar Basin during the Permian–Triassic transition. Here, we describe the fossil woods collected from the base of the Olenekian Shaofanggou Formation in Dalongkou Anticline. Anatomically, these wood remains closely resemble Junggaropitys dalongkouensis, but they lack growth rings and rays are higher. Thus, we suggest identifying them as J. cf. dalongkouensis. The growth pattern shows that J. cf. dalongkouensis is evergreen and developed under warm and humid environments. However, the data of geochemistry, palaeosol and certain sedimentary features reveal a dry climate. Thus, we speculate that the Olenekian Junggar Basin contained gallery forests in the arid environment.