Dinosaur-landscape interactions at a diverse Early Cretaceous tracksite (Lee Ness Sandstone, Ashdown Formation, southern England)

An assemblage of dinosaur footprints is reported from the Lower Cretaceous (Berriasian-Valanginian) Ashdown Formation of East Sussex, southern England. The ichnofauna is concentrated around a 2 m thick stratigraphic marker, the Lee Ness Sandstone, where recent cliff retreat has revealed 85 recognisable footprints attributable to 13 morphotypes, many of which bear high-fidelity skin impressions. The newly identified morphotypes mean that this tracksite hosts one of the most diverse dinosaur ichnoassemblages in the well-documented Mesozoic record of Britain; recording the activity of theropod, ornithopod, thyreophoran and possibly sauropod tracemakers. Most of the footprints were emplaced on a single floodplain mudstone horizon beneath a fluvial crevasse splay sandstone, where preservation was favoured by cohesive sediment and a prolonged interval of sedimentary stasis, during which trackways could be imparted. The sedimentological context of the trackways reveals evidence of interactions between dinosaurs and the riverine landscape that they inhabited; including the development of microtopographies around footprints, which impacted invertebrate burrowing activity, and evidence for dinosaur wading below the bankfull level of small meandering channels and oxbow lakes. Modern analogue suggests that the large dinosaurs may have played a significant role as zoogeomorphic engineers within the ancient floodplain setting, but the imperfect translation of sedimentary environment to sedimentary rock means that geological evidence for such is ambiguous

Archetypally Siluro-Devonian ichnofauna in the Cowie Formation, Scotland: implications for the myriapod fossil record and Highland Boundary Fault Movement

The Cowie Formation of the Stonehaven Group is the lithostratigraphically oldest unit of the Old Red Sandstone in Scotland. A reliable determination of the formation’s age has implications for the arthropod fossil record (as it contains the world’s oldest known fossils of air-breathing myriapoda), the unit’s burial history, and constraints on the timing of the movement of the regionally significant Highland Boundary Fault. Previous studies, utilising different dating techniques, have provided conflicting ages for the unit: middle Silurian (late Wenlock), based on palynomorph biostratigraphy; or Early Devonian (Lochkovian–Pragian), from U-Pb dating of tuffs. Here we report a previously undescribed non-marine trace fossil assemblage that has implications for the age of the Cowie Formation when it is compared with other Siluro-Devonian formations worldwide. The trace fossil assemblage is a low diversity ichnofauna of Arenicolites isp., Taenidium barretti and rare comma-shaped impressions, in addition to sporadic bioturbated layers and sedimentary surface textures of a possible microbial origin. The low ichnodiversity reflects continental (alluvial) deposition during the earlier stages of the global terrestrialization of arthropods. However, the Cowie Formation ichnofauna is more diverse than that from other continental deposits of middle Silurian age, and shares greater similarity with worldwide Pridoli to Devonian-aged ichnofaunas. Here we consider the ichnofauna against two competing hypotheses: (1) that the Cowie Formation records the oldest known non-marine ichnofauna of vertical and back-filled meniscate burrows globally; or (2) that the Cowie Formation is 5–20 Ma younger than is presently documented. Comparing the ichnofauna with contemporaneous deposits worldwide, and considering other unresolved geological issues with the presently-documented age, circumstantial evidence strongly favours the latter hypothesis. Here we suggest that the palynologically-dated strata of the Cowie Formation (inland exposures) represent an older, unrelated, and presently un-named formation, and that the more extensively-exposed fossil-bearing strata were deposited within a narrow stratigraphic window during the early Lochkovian.APS was supported by the Natural Environment Research Council [grant number NE/L002507/1]

The Tumblagooda Sandstone revisited: Exceptionally abundant trace fossils and geological outcrop provide a window onto Palaeozoic littoral habitats before invertebrate terrestrialization

AbstractThe establishment of permanent animal communities on land was a defining event in the history of evolution, and one for which the ichnofauna and facies of the Tumblagooda Sandstone of Western Australia have been considered an archetypal case study. However, terrestrialization can only be understood from the rock record with conclusive sedimentological evidence for non-marine deposition, and original fieldwork on the formation shows that a marine influence was pervasive throughout all trace fossil-bearing strata. Four distinct facies associations are described, deposited in fluvial, tidal and estuarine settings. Here we explain the controversies surrounding the age and depositional environment of the Tumblagooda Sandstone, many of which have arisen due to the challenges in distinguishing marine from non-marine depositional settings in lower Palaeozoic successions. We clarify the terminological inconsistency that has hindered such determination, and demonstrate how palaeoenvironmental explanations can be expanded out from unambiguously indicative sedimentary structures. The Tumblagooda Sandstone provides a unique insight into an early Palaeozoic ichnofauna that was strongly partitioned by patchy resource distribution in a littoral setting. The influence of outcrop style and quality is accounted for to contextualize this ichnofauna, revealing six distinct low-disparity groups of trace fossil associations, each related to a different sub-environment within the high-ichnodisparity broad depositional setting. The formation is compared with contemporaneous ichnofaunas to examine its continued significance to understanding the terrestrialization process. Despite not recording permanent non-marine communities, the Tumblagooda Sandstone provides a detailed picture of the realm left behind by the first invertebrate pioneers of terrestrialization.</jats:p

A graphic method for depicting horizontal direction data on vertical outcrop photographs

Outcrop photographs which show two-dimensional representations of three-dimensionally dipping surfaces (e.g., bedding planes, cross-bed foresets) are commonly utilized in the description of sedimentary strata. In many instances, accurate depiction of the dip direction of such features is paramount for understanding their interpretation, and for visualizing the true form of three-dimensional bodies (e.g., conceptualizing the form of an architectural element in a cliff-face, preserved as a vertical slice that has been cut oblique to paleocurrent direction). However, as an outcrop photograph often presents information on a vertical plane and directional data refers to a horizontal plane, the accurate co-depiction of both sets of information may be challenging. There is presently no universal method for illustrating such measurements on outcrop photographs: techniques in common usage are often imprecise, and the lack of uniformity hinders comparison between different images. Here we present a method for accurately depicting horizontal direction data on vertical outcrop photographs which permits instant visualization of dip relative to the illustrated outcrop geometry. The method is simple to apply, does not compromise primary data, and is unobtrusive to other visual information within images; thus having utility across a broad spectrum of geological investigations

Where does the time go? Assessing the chronostratigraphic fidelity of sedimentary geological outcrops in the pliocene–pleistocene red crag formation, eastern england

It is widely understood that Earth’s stratigraphic record is an incomplete record of time, but the implications that this has for interpreting sedimentary outcrop has received little attention. Here we consider how time is preserved at outcrop using the Neogene-Quaternary Red Crag Formation, England. The Red Crag Formation hosts sedimentological and ichnological proxies that can be used to assess the time taken to accumulate outcrop expressions of strata, as ancient depositional environments fluctuated between states of deposition, erosion and stasis. We use these to estimate how much time is preserved at outcrop scale and find that every outcrop provides only a vanishingly small window onto unanchored weeks to months within the 600-800 ka of ‘Crag-time’. Much of the apparently missing time may be accounted for by the parts of the formation at subcrop, rather than outcrop: stratigraphic time has not been lost, but is hidden. The time-completeness of the Red Crag Formation at outcrop appears analogous to that recorded in much older rock units, implying that direct comparison between strata of all ages is valid and that perceived stratigraphic incompleteness is an inconsequential barrier to viewing the outcrop sedimentary-stratigraphic record as a truthful chronicle of Earth history

Cold feet: Trackways and burrows in ice-marginal strata of the end-Ordovician glaciation (Table Mountain Group, South Africa)

Abstract New observations from an outcrop of Upper Ordovician Table Mountain Group strata (Matjiesgoedkloof, Western Cape Province, South Africa) have revealed an unexpected ichnofauna that is hosted within diamictites and sandstones that were deposited by a retreating low-latitude (∼30°S) ice sheet during the Hirnantian glaciation. The locality provides a rare window onto animal-sediment interactions in an early Paleozoic ice-marginal shallow-marine environment and contains a trace fossil community with a surprising ichnodiversity and ichnodisparity of burrows, trackways, and trails (Archaeonassa, Diplichnites, Heimdallia, Metaichna, ?Multina, Planolites, Protovirgularia, Skolithos). Exceptional phenomena preserved in the strata include evidence for direct colonization of glacial diamictites by deep-burrowing Heimdallia infauna, and interactions between trackways and dropstones on substrates. Observations from the newly recognized outcrop dramatically expand our understanding of deep-time glacial habitats, demonstrating that deglaciating ice margins had already been colonized by the latest Ordovician. The freshwater influx that would have been associated with such settings implies that faunal associations that were tolerant of brackish water were also established by that time. The locality has further significance because it records the activity of a nearshore animal community contemporaneous with the fauna of the nearby Soom Shale lägerstatte. Combined, these features reveal a paleoecological transect of the diverse marine life that inhabited cold-climate, low-latitude shallow seas around the time of the end-Ordovician deglaciation.Cambridge-Africa ALBORADA Research Fun

Evolutionary synchrony of Earth's biosphere and sedimentary-stratigraphic record

The landscapes and seascapes of Earth’s surface provide the theatre for life, but to what extent did the actors build the stage? The role of life in the long-term shaping of the planetary surface needs to be understood to ascertain whether Earth is singular among known rocky planets, and to frame predictions of future changes to the biosphere. Modern geomorphic observations and modelling have made strides in this respect, but an under-utilized lens through which to interrogate these questions resides in the most complete tangible record of our planetary history: the sedimentary-stratigraphic record (SSR). The characteristics of the SSR have been frequently explained with reference to changes in boundary conditions such as relative sea level, climate, and tectonics. Yet despite the fact that the long-term accrual of the SSR was contemporaneous with the evolution of almost all domains of life on Earth, causal explanations related to biological activity have often been overlooked, particularly within siliciclastic strata. This paper explores evidence for the ways in which organisms have influenced the SSR throughout Earth history and emphasizes that further investigation can help lead us towards a mechanistic understanding of how the planetary surface has co-evolved with life. The practicality of discerning life signatures in the SSR is discussed by: 1) distinguishing biologically-dependent versus biologically-influenced sedimentary signatures; 2) emphasizing the importance of determining relative time-length scales of processes and demonstrating how different focal lengths of observation (individual geological outcrops and the complete SSR) can reveal different insights; and 3) promoting an awareness of issues of equifinality and underdetermination that may hinder the recognition of life signatures. Multiple instances of life signatures and their historic range within the SSR are reviewed, with examples covering siliciclastic, biogenic and chemogenic strata, and trigger organisms from across the spectrum of Earth’s extant and ancient life. With this novel perspective, the SSR is recognised as a dynamic archive that expands and complements the fossil and geochemical records that it hosts, rather than simply being a passive repository for them. The SSR is shown to be both the record and the result of long-term evolutionary synchrony between life and planetary surface processes

Short-term evolution of primary sedimentary surface textures (microbial, abiotic, ichnological) on a dry stream bed: modern observations and ancient implications

A wide variety of sub-ripple-scale sedimentary surface textures are known from bedding planes in the sedimentary rock record. Many of these textures were traditionally ascribed an abiotic origin (e.g., due to rain drop impact, adhesion, etc.), but in recent decades the role of microbial mats and biofilms in sculpting and mediating some forms has become increasingly recognized. Microbial sedimentary textures are now well-described and understood from modern tidal environments and biological soil crusts, but descriptions from fluvial settings are less common, despite their known occurrence in ancient alluvium. This paper reports a suite of primary sedimentary surface textures which were observed forming in discrete bodies of standing water in the lower reaches of the ephemeral Murchison River, Western Australia. Microbial sedimentary signatures included bubble impressions (burst and intact) and roll-ups, in addition to reduced horizons. Many of these features exhibited rapid temporal evolution of their morphology in the dry days following an interval of heavy rain. Significantly, these microbial features were witnessed in close spatial proximity to other abiotic and biotic sedimentary surface textures including raindrop impressions, adhesion marks, desiccation cracks, and vertebrate and invertebrate traces. Such proximity of abiotic and microbial sedimentary surface textures is rarely reported from bedding planes in the rock record, but these modern observations emphasize the fact that, particularly in non-marine environments, such structures should not be expected to be mutually exclusive. An appreciation of the fact that primary sedimentary surface textures such as these develop during intervals of stasis in a sedimentation system is crucial to our understanding of their significance and diversity in the rock record.APS was supported by the Natural Environment Research Council [grant number NE/L002507/1]. WJM was supported by Shell International Exploration and Production B.V under Research Framework 604 agreement PT38181

Non-palimpsested crowded Skolithos ichnofabrics in a Carboniferous tidal rhythmite: Disentangling ecological signatures from the spatio-temporal bias of outcrop

Funder: International Association of Sedimentologists; Id: http://dx.doi.org/10.13039/501100007463A heterolithic tidalite succession yielding spring–neap bundles is newly reported from a mid- Carboniferous (Serpukhovian) section of the Alston Formation of Northumberland, England. The rhythmite records deposition over an interval that can be confidently calibrated to at least 84 lunar days, and attests to a non-negligible tidal range in parts of the Northwest European Seaway in the late Mississippian. The tidalite is notable for the presence of a striking crowded Skolithos ichnofabric on both bedding planes and in vertical section. Bedding plane expressions of the ichnofabric reveal true substrates of sand piles excavated during burrow construction, in addition to an apparently remarkable equal spacing between individual burrows that is shown to be genuine through pair correlation function analysis. These characteristics show that the burrowed horizons were registered by contemporaneous ichnocoenoses, with no palimpsesting of burrows. The irregular vertical distribution of burrow horizons, despite a near-continuous semi-diurnal record of sedimentation, is suggested to be an artefact of spatial patchiness of burrowing communities in the depositional environment; imperfectly registered in a vertical profile with high-temporal, lowspatial resolution. The succession proves that burrow palimpsesting is not an inevitable ichnological conclusion of sedimentary stasis, and attests to intermittent palaeoecological fidelity of the stratigraphic record at the small spatio-temporal scales recorded a

Persistent Place-Making in Prehistory: the Creation, Maintenance, and Transformation of an Epipalaeolithic Landscape

Most archaeological projects today integrate, at least to some degree, how past people engaged with their surroundings, including both how they strategized resource use, organized technological production, or scheduled movements within a physical environment, as well as how they constructed cosmologies around or created symbolic connections to places in the landscape. However, there are a multitude of ways in which archaeologists approach the creation, maintenance, and transformation of human-landscape interrelationships. This paper explores some of these approaches for reconstructing the Epipalaeolithic (ca. 23,000–11,500&nbsp;years BP) landscape of Southwest Asia, using macro- and microscale geoarchaeological approaches to examine how everyday practices leave traces of human-landscape interactions in northern and eastern Jordan. The case studies presented here demonstrate that these Epipalaeolithic groups engaged in complex and far-reaching social landscapes. Examination of the Early and Middle Epipalaeolithic (EP) highlights that the notion of “Neolithization” is somewhat misleading as many of the features we use to define this transition were already well-established patterns of behavior by the Neolithic. Instead, these features and practices were enacted within a hunter-gatherer world and worldview