Palaeoenvironmental Interpretation Research Articles

Late Quaternary palaeoenvironmental controls on concentric talus evolution in the Central Ebro Basin (NE Spain)

The polyphasic evolution of the testimonial buttes in the central area of the Ebro basin (Los Monegros) is analysed. This is a semiarid area that favours high erosion rates. An evolutionary model of the Jubierre hills is presented that shows the environmental cycles represented by aggradational and degradative processes on the slopes that resulted in the present arrangement of talus flatiron rings. In the four studied cases, talus relicts are composed of detritic material from a disappeared caprock pediment. Four slope stages (S4 to S1) that formed under stable climate conditions are identified. Older stages (S4 and S3) are estimated by comparison with other talus flatirons in the region. The S2 stage contains Bronze Age archaeological remains and the radiocarbon age obtained was 1608–1446 years cal BC (2σ), while S1 is younger. A palaeoenvironmental interpretation was made for these aggradational stages (S4 to S1). The active erosion of these hills led to a relief inversion, and talus flatirons remain as the only features revealing the presence of the relict hills and past human occupations.

Stratigraphic reassessment of Grotta Romanelli sheds light on Middle-Late Pleistocene palaeoenvironments and human settling in the Mediterranean

During the last century, Grotta Romanelli (Southern Italy) has been a reference site for the European Late Pleistocene stratigraphy, due to its geomorphological setting and archaeological and palaeontological content. The beginning of the sedimentation inside the cave was attributed to the Last Interglacial (MISs 5e) and the oldest unearthed evidence of human occupation, including remains of hearths, was therefore referred to the Middle Palaeolithic. Recent surveys and excavations produced new U/Th dates, palaeoenvironmental interpretation and a litho-, morpho- and chrono-stratigraphical reassessment, placing the oldest human frequentation of the cave between MIS 9 and MIS 7, therefore embracing Glacial and Interglacial cycles. These new data provide evidence that the sea reached the cave during the Middle Pleistocene and human occupation occurred long before MISs 5e and persisted beyond the Pleistocene- Holocene boundary.

Palynostratigraphy and Palaeoenvironmental Interpretation of Outcrop Formations in Parts of Ini-Akwa Ibom State, Southeastern Niger Delta Basin, Nigeria

The palynological study of the outcrop Formations in parts of Ini Local Government Area of Akwa Ibom State, Southeastern Niger Delta Basin, Nigeria has contributed to unraveling the palynostratigraphy and paleoenvironments of the outcrops through the use of diagnostic palynomorphs. The section is made up of carbonaceous shales, sandstones, mudstones and claystones. The conventional maceration technique for recovering acid-insoluble organic-walled microfossils from sediments was used to prepare twenty outcrop samples for palynological studies. The samples produced poor to fair diversity assemblages of palynomorphs. A total of 176 palynomorphs species were recorded, with 48% pollen grains, 33% spores, 12% dinoflagellate cysts, 5% fungal spores, and 2% microforam test wall linings. Based on stratigraphically selected index taxa recovered,age determination and correlation wereestablished. The samples from Imo Formation were assigned Late Paleocene-Eocene based on Psilatricolporites Crassus, Retitricolporites irregularies, Psilatricolporites sp. and Leiotriletes adriennis with the presence of Paleocene dinoflagellate cysts such as Lejeunacysta beninensis and Selenopemphix nephroides. Ameki samples were dated Early-Middle Eocene based on Proxapertites operculatus, Retistephanocolpites williamsi, Mauritidites crassiexinius, Monocolpites marginatus and Longapertites marginatus. Ogwashi-Asaba shale samples were assigned Late Eocene-Early Oligocene due to the abundant presence of Verrucatosporites usmensis, Laevigatosporites discordatus and Retitricolporites irregularis while Eze-Aku samples were tentatively assigned Paleocene because of the presence of two pollen index fossils Proxapertites operculatus and Pachydermites diederixi. Inferred depositional conditions suggest that Imo Formation was deposited in a shallow marine or near shore brackish water estuarine environment. The Ameki Formation was accumulated in a marginal marine or near shore, brackish water-estuarine environment in the upper deltaic setting. The Ogwashi-Asaba Formation was deposited in a progradational shoreline moving between the brackish water and fresh water deltaic plain. The Eze-Aku Formation was deposited in an upper foreshore fresh water environment. The palynological study of the samples are Paleogene Formations while the paleoenvironment is in a costal deltaic to shallow-marine environment and are appropriate for hydrocarbon accumulations and exploration.

Lycopsid Lepacyclotes Emmons from the Middle Triassic of the Ordos Basin, North China and reviews of the genus

Lepacyclotes Emmons is one of the most important Early-Middle Triassic lycopsids, a genus that became extinct during the Late Triassic-Jurassic. Due to its relatively short geological ranges, fairly wide geographic distributions, and strict palaeoecological requirements, this genus is important in stratigraphical correlation and palaeoenvironmental interpretation. Although this lycopsid has been studied for more than a century, there are less than 20 species of Lepacyclotes are known. In this paper, we report abundant new materials from the upper Middle Triassic of the Ordos Basin, North China for the first time. Two species are identified: Lepacyclotes zeilleri (Fliche) Retallack and L. ordosensis Deng sp. nov., with the former species yielding numerous in situ megaspores. Precise absolute dating of tuff layers intercalated in the strata bearing Lepacyclotes point to the early Ladinian (Middle Triassic). A comprehensive analysis of the previous data shows that the genus Lepacyclotes originated during the Early Triassic in multiple areas, flourished in late Early Triassic to early Middle, and strongly declined in the Middle Triassic. A few relicts survived in the Late Triassic and Early Jurassic. Lepacyclotes was adapted to salty, seawater-associated, or evaporative environments. Additionally, the generic diagnosis of Lepacyclotes is emended, and the relationships between the genus and its related genera have been discussed.

Electro-sequence analysis and natural resources potential of a transitional environment in central swamp depobelt, Niger delta, Nigeria

Sequence stratigraphy and Electrosequence of the Don-Field Central Swamp depobelt of the Niger Delta Basin, was carried out using well logs, biostratigraphic and core data. The aim of this study is to re-characterise and revalidate the reservoirs within the study area and provide an optimum framework for predicting reservoir character, development and reservoir quality distribution. Detailed petrophysical evaluation reveals proficient hydrocarbon reservoir units with variable parameters (i.e. porosity, permeability and shale volume) that can accommodate productive hydrocarbon reserve. Core data analyses revealed heavy minerals like pyrites and glauconites that can be of economic interest. The gamma wireline signatures of the wells show reservoir units that are predominantly blocky in shape indicative of fluvial channels. Fluvial channels are typically associated with coastal and/or marginal marine environments. More so, the aforementioned observations were validated using palaeoenvironmental interpretation of strata penetrated by Well-1, Well-2, and Well-3 via the sidewall core analyses. Sequence stratigraphic surfaces such as maximum flooding surfaces (MFS) and sequence boundary (SB) were observed to show good correlation with palynological and foraminiferal zones. The stacking patterns (i.e. progradation, retrogradation and aggradation) encountered gave acumen into systems tracts (i.e. lowstand system tract (LST), transgressıve system tract (TST) and highstand system tract (HST) interpretation. These system tracts constitute a depositional sequence set of middle—late Miocene age bounded chronologically by MFS of 9.5 Ma, 12.8 Ma, 15.0 Ma, 15.9 Ma and SB of 12.1 Ma, 13.1 Ma, 15.5 Ma, 15.9 Ma. The SB and MFS were delineated based on Shell Petroleum Development Company (SPDC) biozonation scheme: F-zone and P-zone were within P820-P680 and F9500-F9600/F9700 as contained in the biofacies interpreted data of index fossils (Globorotalia foshi S.I; Globorotalia praefohsi; Globorotalia peripheroacuta; Orbulina spp; Praeorbulina sicana; Paragloborotalia mayeri; Neogloboquadrina acostaensis) which corresponded to the alphanumeric code N8–N16 planktonic foraminiferal zones of Blow.

Critical evaluation of geochemical indices of palaeosalinity involving boron

Despite years of research, palaeosalinity remains one of the most difficult palaeoenvironmental proxies to reconstruct. Numerous approaches have been proposed. Those utilising boron, gallium, strontium, barium, and potassium are among the most commonly used in palaeoenvironmental reconstructions. The comparison of chemical and mineralogical data obtained for hundreds of samples from various sedimentary basins of different ages and burial histories indicated that those proxies are highly sensitive to detrital and authigenic mineralogy changes. It has been shown that boron is preferentially accumulated in the 2:1 clays (illite 1Md and 2M1, illite–smectite), 1:1 clays (kaolinite), and hematite, which all are of non-synsedimentary origin. An increase in the weathering products input, high flux of the detrital mica, and/or enhanced burial diagenesis may increase B/K and B/Ga ratios, suggesting the marine environment of deposition. On the other hand, an increased input of the detrital K-feldspars or plagioclases may decrease those ratios implying freshwater sedimentation. Mineralogy is also responsible for the Sr/Ba ratio variability, resulting in spurious palaeoenvironmental interpretations. Isotope techniques may be more appropriate, especially if the finest clay fractions are used and the diagenetic fluid flow is confined to the analysed basin.

Palaeoenvironmental interpretation based on lithofacies derived from Keera Dome, Kachchh, western India

Palaeoenvironmental interpretation based on lithofacies derived from Keera Dome, Kachchh, western India

Palaeoenvironmental reconstruction of the late Miocene macroflora of La Bisbal d'Empordà (Catalonia, Spain). Comparison with small mammals

The late Miocene flora from La Bisbal d'Empordà (Catalonia, Spain) provides significant data for characterising the coastal vegetation from the north-eastern Iberian Peninsula during a key period in Neogene climatic evolution. To this end, a historical leaf collection from La Bisbal d'Empordà was re-examined, analysed from a palaeoenvironmental viewpoint and compared with data provided by the associated small mammal fauna. This flora dates from 9.6–9.7 Ma in age (early Tortonian) according to small mammal biostratigraphy.The fossil-bearing beds were deposited in the floodplain of a meandering river system. Three palaeoecological assemblages were recognized: 1) Helophytic plant stems related to a wetland community. 2) Torn leaves of Fraxinus sp., Ulmus sp., Zelkova sp., Cedrelospermum sp. Populus balsamoides, Alnus gaudinii, Carpinus sp., Platanus sp., Acer tricuspidatum, Daphnogene sp. and, Laurophyllum sp. which would have belonged to a riparian forest located beyond the wetland community, with Fraxinus being the plant growing in closest proximity; 3) Isolated complete Paliurus seeds, interpreted as mainly wind-transported, which provide evidence of an open and more arid landscape situated distally from the floodplain. The small mammal assemblages associated with this flora are consistent with this palaeoenvironmental interpretation. The paucity of small arboreal mammal taxa and insectivores suggests limited forested vegetation areas, while the more common terrestrial species indicate better developed open landscapes. Our results show a more heterogeneous environment than previously thought and that the riverine processes impinged the flora, somewhat limiting the climatic conclusions that might be derived from leaf physiognomic analyses such as CLAMP.

Palynofacies of the early Cretaceous Pariwar Formation, Jaisalmer Basin, Rajasthan, India: Palaeoenvironmental interpretation

Palynofacies of the early Cretaceous Pariwar Formation, Jaisalmer Basin, Rajasthan, India: Palaeoenvironmental interpretation

Carbon and oxygen stable isotope record of upper Kimmeridgian shallow-marine ramp carbonates (Iberian Basin, NE Spain): the imprint of different burial and tectonic histories

Bulk carbon and oxygen stable isotopes of ancient shallow-marine carbonates can record the effects of multiple palaeoenvironmental factors, but also the imprint of several post-depositional processes, which may alter the original marine isotopic composition. In this study, carbon and oxygen stable isotope analyses were performed on bulk carbonate, bivalve calcitic-shell (Trichites) and calcite vein samples from two stratigraphic sections (Tosos and Fuendetodos, present-day distance 15km), representing proximal inner- and distal mid-ramp environments, respectively, of the uppermost Kimmeridgian ramp facies deposited in the northern Iberian Basin (NE Spain). These successions underwent different diagenetic pathways that altered the primary marine isotopic composition in each section in different ways. Different burial histories, tectonic uplift and a variable exposure to meteoric diagenesis from the end of the Kimmeridgian to the Cenozoic (following Alpine tectonic uplift) are reflected in the different alteration patterns of the carbon and oxygen stable isotope signatures. A significant deviation to lower values in both δ13O and δ18O is recorded in those carbonates mostly exposed to meteoric diagenesis (distal mid-ramp Fuendetodos section), because of post-depositional tectonic uplift (telogenesis). On the other hand, the deposits mainly affected by burial diagenesis (proximal inner-ramp Tosos section) only record low δ18O with respect to expected values for pristine Kimmeridgian marine carbonates. The different burial and tectonic uplift histories of these deposits in each sector, due to their different tectonic evolution in this part of the basin, resulted in a variable degree of diagenetic resetting. However, in spite of the different diagenetic resetting reported of the carbon and oxygen stable isotope signatures in each section, these carbonates show similar cement types in termsof fabrics and cathodoluminescence properties. The diagenetic resetting reported for these carbonates prevents the use of the δ13O and δ18O records for addressing palaeoenvironmental interpretations, but instead highlights useful features regarding the variable diagenetic overprint of the studied shallow-marine carbonate successions concerning their specific post-depositional history.

Descending into the “snowball”: High resolution sedimentological and geochemical analysis across the Tonian to Cryogenian boundary in South Australia

The Tonian–Cryogenian transition (ca. 720 Ma) represents a period of significant environmental change in Earth history, involving variations in oceanic and atmospheric oxygenation, significant changes in the biosphere, tectonic reorganisation, and the onset of the global ‘Sturtian’ glaciation. South Australia has some of the thickest, continuous and best exposed sections of this unique interval globally. Here we present detailed palaeoenvironmental interpretations for a complete, ca. 3 km thick, pre- to post-glacial succession near Copley in the northern Flinders Ranges, South Australia. Elemental concentration data, complemented by screening for diagenesis, demonstrates the preservation of marine or primary REE signatures for studied carbonate samples and supports the proposed sedimentological and palaeoenvironmental interpretations. Multiple Tonian regressive-transgressive cycles are defined, which are recorded by deltaic rippled and cross-stratified sandstones (Copley Quartzite), through inner platform intraclastic magnesite and stromatolitic carbonates (Skillogalee Dolomite), to subtidal laminated siltstone and platform carbonates (Myrtle Springs Formation). The REE patterns from carbonate samples in the Skillogalee Dolomite and Myrtle Springs Formation indicate low Y/Ho, slight light rare earth element (LREE) depletion, weak negative Ce/Ce* and high Eu/Eu*. This suggests a nearshore, dysoxic setting fed by anoxic deep waters and more oxic shallow waters. In combination, the sedimentological and geochemical data build a picture of a partially restricted, shallow marine to lagoonal setting for the northern Flinders Ranges directly before the climate pivot to the Sturtian glaciation. These pre-glacial formations are unconformably overlain by Cryogenian subglacial to grounded ice-margin pebbly diamictites with immature, massive sand interbeds (Bolla Bollana Tillite). We suggest these facies reflect glacial grounding-line advance and retreat in a glaciomarine setting. These grade into turbiditic laminated sandstone and mudstone with dropstones (Wilyerpa Formation), which were likely deposited at the onset of deglaciation in a subaqueous proglacial environment. The post-glacial succession (Tapley Hill Formation) consists of subtidal laminated shales and carbonates, which are represented by increased Y/Ho, moderate LREE depletion, slight negative Ce/Ce* and low Eu/Eu*. This significant geochemical shift to a more open, oxic to suboxic subtidal setting coincides with widespread transgression and relative sea level rise after one of the most severe glaciations ever recorded.

Uppermost Triassic to Lower Jurassic stratigraphy in the Lough Foyle Basin of County Londonderry, Northern Ireland

The Lough Foyle Basin is a half-graben that straddles the border between Northern Ireland and the Republic of Ireland and contains sediments that range in age from Lower Carboniferous to Holocene. The basin’s post-rift succession is represented by sediments of the Penarth Group and Lias Group. The lithostratigraphy and biostratigraphy of that interval are revised using new borehole material and existing outcrop. Palaeontological data provide a chronostratigraphic framework and aid palaeoenvironmental interpretations. Foraminifera, ostracods, palynomorphs indicate a nearshore, marginal marine depositional setting throughout much of the Rhaetian with a more marine, shelf and nearshore depositional setting for the Lias Group. The Penarth Group succession is similar to that elsewhere in Northern Ireland but the Lias Group (Waterloo Mudstone Formation) differs in that five distinct members can be recognised (Clooney Mudstone, Drummans Siltstone, Gortmore Mudstone, Tircreven Sandstone and Ballyleighery Mudstone), four of which are newly described. The deltaic and shelf sandstones of the Tircreven Sandstone Member are the only such examples preserved in the Jurassic strata of Northern Ireland and are some of the oldest in the Jurassic of the UK and Ireland, providing evidence of the proximity of the nearby Irish Landmass and representing a useful comparison for Early Jurassic sandstone reservoirs in offshore basins.

Times are changing: A new chronology for Holocene volcanic events and hydro-sedimentary history recorded in the Sarliève marsh (central France)

This paper presents the first well-dated palaeoenvironmental study from the Sarliève marsh, a unique sedimentary record in the Limagne plain of central France, where all previous studies suffered from unreliable chronologies. We developed an accurate radiocarbon-based age-depth model and performed high-resolution multi-proxy sedimentological and geochemical analysis on a new sediment core from the heart of the sedimentary basin, improving the chronology and Holocene palaeoenvironmental interpretations. We found six potential (crypto)tephra fallouts (c. 9750, 8500, 7500, 7400, 6300, and 5800 cal yr BP) that enrich the Holocene tephrostratigraphy in Limagne, five of which were not previously documented in the sediments of the marsh. We also detected, for the first time, an array of volcanic phenomena such as degassing episodes (c. 6950 and 6050 cal yr BP), ash leaching phases (10250–9750, 8500–7400, and 5800–5100 cal yr BP), and earthquakes (c. 6800, 6600, 6050, 6100, and 1600 cal yr BP), suggesting a hitherto unsuspected period of high volcanic activity in the area between 7500 and 5800 cal yr BP. This increased activity appears to have caused a massive forcing of hydrosedimentary dynamics in the catchment in the Middle Holocene, by supplying significant volumes of fine volcanic ash to the palustrine basin, and thereby questioning the current Holocene morpho-sedimentary narrative for Limagne. The basin became a permanent freshwater lake after the Mid-Holocene climatic shift, and detrital influxes likely due to anthropogenic soil erosion appeared c. 5500 cal yr BP and grew steadily after 5000 cal yr BP, with a marked lull between 3600 and 3000 cal yr BP, perhaps because of a phase of settlement abandonments during the middle and early-late Bronze age. A series of lacustrine low-stands (c. 4750–4600, 3750–3600, 3350–3200 and 2950–2800 cal yr BP) that correlate strongly with western alpine lake records do not seem to have caused significant changes in the anthropogenic impact on soils modifying the sedimentary supply. Our results suggest that this lake could have been artificially drained c. 2550 cal yr BP, several centuries earlier than previously estimated, allowing us to hypothesize that Early Iron age societies already had substantial capacity to modify the hydraulic environment. Hydromorphic conditions developed thereafter, including complex short-lived marshy phases in late Roman times.

Advances and Challenges in Palaeoenvironmental Studies Based on Oxygen Isotope Composition of Skeletal Carbonates and Phosphates

Oxygen isotopes are widely used in palaeoenvironmental and palaeoclimatic studies as they record variations in the precipitation temperature of biogenic carbonates and phosphates. Problems associated with the preservation state of fossils, selection of the proper temperature equation, vital effects occurring during biomineralization, habitat effects of organisms as well as salinity, bathymetry and water circulation changes limit, however, the applicability of oxygen isotopes to reconstruction of ancient environmental settings. The progress of oxygen isotope studies, temperature calculations and ambiguities of the isotope record are discussed in this paper. The same applies to the methods of retrieving reliable temperature signals and the record of water chemistry changes based on well-preserved calcareous and phosphatic fossils. Sometimes neglected importance of sedimentological and faunistic data associated with sea-level changes and salinity variations is emphasised as an important tool for refinement of the temperature trends of epeiric sedimentary basins. In addition, published case datasets and new laboratory techniques, including micro-area and clumped isotope analyses, are presented to demonstrate examples and prospective ways of extension of the scope of palaeoenvironmental research. The provided information may be used in discussion and a critical review of published oxygen isotope data and their palaeoenvironmental interpretations.

Upper Pliocene bivalve shell concentrations from the Lower Chelif basin (NW Algeria): Systematics, sedimentologic and taphonomic framework

Sedimentologic and palaeontological investigation of the Upper Pliocene Slama Formation in the Lower Chelif Basin (NW Algeria) led us to collect important bivalve assemblages for taxonomic and taphonomic purposes. A rather comprehensive inventory list of Upper Pliocene bivalves from northwestern Algeria is now available and consists of 30 species, 17 of which are extinct ones. Four principal taphonomic attributes were analysed: bioerosion, encrustation, fragmentation, and abrasion. Physical and biogenic sedimentary structures are used for palaeoenvironmental interpretations. The taphonomic, sedimentologic and ichnological characteristics of most of the deposits suggests they originated from discontinuous processes of winnowing and bypassing of sediments, probably due to the action of storms in shallow waters, mainly in the shoreface depositional environment. The bivalve assemblage is dominated by disarticulated valves and displays significant taphonomic alteration in the shells. Sclerobionts traces in shells particulary affect the oyster shells. Bioerosion traces are predominately those of clionid sponges (Entobia isp.), polychaetes (Maeandropolydora isp. and Caulostrepsis isp.), bivalves (Gastrochaenolites isp.), and of predatory gastropods (Oichnus isp.). Among the sclerobionts, the identified encrusters were juvenile oyster recruits, barnacles, polychaetes (serpulid tubeworms), bryozoans (Microporella sp. and Acanthodesia sp.), and vermetid gastropods (Petaloconchus intortus).

Stratigraphy and palaeoenvironmental interpretation of late Quaternary colluvial slope deposits in southern Africa

AbstractSlope and lowland sediment systems throughout southern Africa are dominated by the presence of colluvium with interbedded palaeosols and hardground duricrusts. These sediments correspond to phases of land surface instability and stability, respectively, during the late Quaternary. This study examines the stratigraphy and environmental interpretation of slope sediment records from specific sites in southern Africa for the period of marine isotope stages (MIS) 6 to 1 (~191 ka to present), informed by theoretical ideas of the dynamics of slope systems including sediment supply and accommodation space. Based on this analysis, phases of land surface instability and stability for the period MIS 6 to 1 are identified. The spatial and temporal patterns of land surface conditions are not a simple reflection of climate forcing, but rather reflect the workings of slope systems in response to climate in addition to the role of geologic, edaphic and ecological factors that operate within catchment-scale sediment systems. Considering these systems dynamics can yield a better understanding of the usefulness and limitations of slope sediment stratigraphies.

The functional performance of productidine brachiopods in relation to environmental variables

Fossils are useful as palaeoenvironmental indicators when evaluated using large occurrence and lithology association data sets and/or functional morphology. However, when functional morphology is invoked on an ad hoc basis there exists a risk of circular reasoning. Performance spaces/landscapes constructed using biomechanical experiments can be used to tie performance to morphology quantitatively. They can be used to estimate fitness and function in specific environments by allowing multiple specific measures of function to be evaluated simultaneously. Absolute performance can be used to constrain palaeoenvironmental interpretations by detecting functional limits. We constructed a performance space with four variables (transport resistance, settling time, settling orientation and respiration potential) relating to hydrodynamic and metabolic variables. We combine new performance data with existing palaeoenvironmental interpretations and associated distributions of brachiopods of the suborder Productidina during the late Carboniferous and early Permian in the North American Midcontinent. Productidines were chosen because they lacked pedicles and relied on body and spine morphology to interact with their environment. Offshore dysoxia-associated taxa had increased resistance to sinking and proportionally larger lophophores, potentially improving survivorship in low-oxygen, soft substrate environments. Taxa associated with nearshore and oxygenated offshore environments display a range in performance consistent with a range of conditions, but all had proportionally smaller lophophores. Models that are less stable in high-velocity flows consistently settle in the correct convex down orientation if entrained, while more stable models did not. Our study suggests that as productidines radiated during the Carboniferous, they also differentiated within the performance space.

BRITISH MILITARY CONTRIBUTIONS TO THE GEOLOGY OF MALTA, PART 1: NINETEENTH CENTURY FOUNDATIONS

Malta, an island in the central Mediterranean Sea, was fortified as a base for the Knights Hospitaller 1530–1798 and to provide major harbours for the British Royal Navy after 1813. Men with British military associations (all subsequently to attain some distinction in public and/or academic life) were amongst the many pioneers of Maltese geology who established the essence of its outcrop stratigraphy and structure: a circa 300-metre-thick sequence of near-horizontal mid-Cenozoic fossiliferous limestones punctuated by a ‘blue clay/marl’, cut by a series of major faults and penetrated by several caves and fissures whose infill contained significant remains of Pleistocene vertebrates. Between 1843 and 1856, Lieutenant (later Vice-Admiral) Thomas Abel Brimage Spratt (1811–1888) defined major units in the bedrock sequence, Colonel (later Major-General) Sir William Reid (1791–1858) promoted publication of a geological memoir, and a 1:31,680-scale geological map prepared by the 3rd Earl of Ducie on a Royal Engineers topographical base map was published under Royal Engineer auspices. Mostly between 1860 and 1866, Captain (later Professor) Frederick Wollaston Hutton (1836–1905) and Surgeon (later Deputy Surgeon-General and Professor) Andrew Leith Adams (1827–1882) made field observations that refined earlier interpretations of stratigraphy and structure and generated revised but small-scale maps. They also collected specimens that facilitated specialist identifications of Malta’s fossil faunas, including foraminifera by Thomas Rupert Jones (1819–1911), Professor of Geology at the Royal Military College, Sandhurst. Rock specimens were sent in 1888 by Surgeon-Captain David (later Surgeon-General Sir David) Bruce (1855–1931) and the former engineer Lieutenant (and later Professor) Osbert Chadwick (1844–1913) to the pioneer oceanographer John (later Sir John) Murray (1841–1914). They stimulated Murray’s benchmark study 1889–1890 of Malta’s sedimentary sequence and fossil foraminifera, and their palaeoenvironmental interpretation, plus his compilation of a 1:129,254-scale geological map. These prompted extensive local studies and collection of macrofossil specimens by schoolmaster (later Lieutenant-Colonel) John Henry Cooke (1862–1933). By the end of the century, representative Maltese fossils had been presented for specialist study and identification or description to major museums in England, Scotland and Italy, facilitating improved correlation of Maltese strata with Oligo-Miocene successions elsewhere.

Dinoflagellate cyst assemblages of the Cunga - Quifangondo cenozoic formations in the Cabo São Brás section, Kwanza Basin (Angola): towards a first stratigraphic and paleoenvironmental interpretation

This work introduces one of the first palynostatigraphic study conducted on formations from the Eocene and overlying lowermost Miocene successions (Cunga and Quifangondo formations) exposed in the Onshore Kwanza Basin, Angola.To improve the Cunga and Quifangondo formations age, new biostratigraphic correlations and palaeoenvironmental interpretations based on qualitative and quantitative analyses of organic walled dinoflagellate cysts from sedimentary rocks sampled in the Cabo de São Brás section were obtained.Those works have revealed that the Cunga Formation could be assigned to a middle Eocene - early Oligocene age, with a palynomorph signature typical of outer neritic to oceanic environments (dominance of dinocysts with microforaminiferal linings and radiolarian pyritized fragments).The lower Quifangondo Formation could be assigned to late Oligocene (latest Chattian) - early Miocene (Aquitanian) ages. This assumption is based on the first occurrence of Ectosphaeropsis burdigalensis, and the last occurrence of Deflandrea spp. and Chiropteridium galea. Additionally, the Chiropteridium, Distatodinium, Homotryblium, Hystrichokolpoma and Lingulodinium acme endorses a latest Chattian-early Aquitanian age to these samples. The palynomorph signature of this unit reflects an outer neritic environment.The latest Oligocene/early Miocene Quifangondo Formation overlaps unconformably on strata of the middle Eocene to early Oligocene Cunga Formation, pointing out a hiatus between the two units.

Cryptic burrow traces in black shales – a petrographic Rorschach test or the real thing?

AbstractIn black shale studies, apparent lack of bioturbation is commonly taken as an indication of anoxic bottom waters. Yet, modern oxygen‐stressed environments show that even at suboxic levels (0.0 to 0.2 ml l−1 oxygen), microscopic eukaryotic benthic organisms live in the uppermost millimetres to centimetres of the substrate. Known as meiofauna, these organisms disturb the primary fabric as they move through the sediment. These modern examples inspired students of the rock record to report sub‐millimetre irregular–wiggly features in black shale thin sections as meiofaunal burrows. Preparation flaws in thin section manufacture can cause reduced light transmission that results in darkened regions when viewed in transmitted light, and one wonders whether micro‐burrows reported in the literature are indeed burrows, or alternatively artifact‐induced optical illusions. Examining shale thin sections of Archean to Tertiary age showed: (i) that burrow‐like features are common regardless of age; and (ii) that burrow identification varies significantly between observers. When transposing locations of presumed traces onto scanning electron microscope images of the same field of view (diamond polished surface), no evidence of fabric modification at locations of presumed burrows was observed. Microfabric within and outside ‘burrows’ was the same, and larger fabric elements traversed ‘burrows’ uninterrupted. Once both sides of the rock slice were polished, presumed burrows could no longer be observed, indicating that damage to the underside of the thin section caused the mistaken identification of micro‐burrows. Because burrows emplaced in water‐rich muds must undergo substantial compaction‐induced ‘flattening’ and deformation prior to lithification, geometries of presumed burrows that disagree with a plausible compaction regime provide an additional filter to separate potential burrows from artifact‐induced features. Recognizing meiofaunal disruption is an important aspect for accurate palaeoenvironmental interpretation of black shales. Yet, initial assessment via optical microscopy needs to be verified through scanning electron microscope‐based examination of shale fabrics.