Saint Albans, United Kingdom
Saint Albans, United Kingdom

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Payros A.,University of the Basque Country | Ortiz S.,University of the Basque Country | Ortiz S.,PetroStrat Ltd. | Millan I.,TNO | And 3 more authors.
Bulletin of the Geological Society of America | Year: 2015

The early Eocene climatic optimum, which constituted the peak of the long-term early Cenozoic global warming, had a significant impact on the environmental evolution of terrestrial and oceanic areas. Surprisingly, however, its influence on continental margins is poorly known. New insights are provided from a sedimentological, stable isotope, mineralogical, and micropaleontological study of an 1100-m-thick Lower-Middle Eocene deep-marine succession that accumulated on the North Iberian continental margin. The early Eocene climatic optimum is represented by a 410-m-thick interval characterized by scarcity of hemipelagic limestones, abundance of dark marls, which record a reduction in calcium carbonate content and an increase in kaolinite, and the occurrence of conspicuous red layers with high siderite and pyrite content. Series of stratigraphically significant events frame the early Eocene climatic optimum. Based on this analysis, the environmental influence of the early Eocene climatic optimum started at 52.6 Ma and lasted ~2.3 m.y. Its onset is marked by rapid drops in δ13C and δ18O, which record the addition of 13C-depletedcarbon into the ocean-atmosphere system for 80 k.y. and a concomitant warming. A hotter climate and a perennial rainfall regime increased the supply of terrestrial clays, organicmatter, and iron oxides into the sea. Eventually, these changes affected the deepsea bottom 270 k.y. after the onset of the early Eocene climatic optimum, creating conditions in which opportunistic benthic foraminifera thrived, and leading to increased methanogenesis in the subsurface, which caused the formation of siderite. A subsequent gradual recovery culminated abruptly at 50.3 Ma with a global cooling episode, which is locally recorded by the accumulation of lowstand resedimentation deposits. © 2015 Geological Society of America.


Reggiani L.,PetroStrat Ltd | Reggiani L.,University of Perugia | Reggiani L.,French National Center for Scientific Research | Mattioli E.,French National Center for Scientific Research | And 4 more authors.
Marine Micropaleontology | Year: 2010

Quantitative analysis of Early Jurassic calcareous nannofossil assemblages from the Peniche section in Portugal have been performed in order to interpret palaeoenvironmental changes occurring in the Lusitanian Basin during the Late Pliensbachian Davoei, Margaritatus and Spinatum Ammonite Zones. Nannofossil data are compared to already published carbon and oxygen stable isotope data, organic matter content (wt.%Total Organic Carbon, TOC), and biomarker analysis. A significant change in calcareous nannofossil assemblages and species diversity at the transition between the Margaritatus and Spinatum Ammonite Zones matches with the pattern shown by geochemical data. This suggests that a profound change in environmental conditions occurred at that time. In the Davoei and Margaritatus Ammonite Zones, in a context of general sea-level rise, the Lusitanian Basin was characterized by water column stratification that favoured the sedimentation and preservation of organic matter. Biomarkers and oxygen isotope trends suggest that stratification of water masses occurred because of low salinity in surface waters. The shallowest part of the water column, characterized by oligotrophic conditions, was inhabited by the (probable) calcareous dinocyst Schizosphaerella spp., while the deep-dweller Crepidolithus crassus flourished in the lower photic-zone layers. In the Spinatum Ammonite Zone, a regressive trend occurred and a salinity increase is inferred on the basis of oxygen isotope values. Water masses were probably less stratified at that time. The upper photic-zone nannofossil assemblages were still dominated by Schizosphaerella spp. whilst, in the deep photic-zone, Mitrolithus jansae (a Mediterranean taxon) replaced C. crassus (a taxon with NW-European affinity). This pattern may indicate a change in palaeoceanographic conditions related to surface current circulation. The sea-level fall occurring during the Spinatum Ammonite Zone may have resulted in the partial isolation of the Lusitanian Basin from the NW-Europe basins because of the creation of a threshold. Alternatively, tectonic drowning of North African carbonate platforms in the Late Pliensbachian may have promoted better exchanges of nannoplankton between the Lusitanian Basin and the Mediterranean Tethys via the creation of new seaway connections. © 2010 Elsevier B.V. All rights reserved.


Ortiz S.,University of the Basque Country | Ortiz S.,PetroStrat Ltd. | Thomas E.,Yale University | Thomas E.,Wesleyan University
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2015

The early-middle Eocene transition (EMET, ~51-47Ma) was a pivotal time in Cenozoic global climate development, encompassing the end of the Early Eocene Climate Optimum (EECO) and the start of high-latitude cooling, culminating in the early Oligocene Glacial Maximum (34-33Ma). We studied benthic foraminiferal assemblages and stable isotopes at upper abyssal Site 1263 (paleodepth ~1800m) and lower abyssal Site 1267 (paleodepth ~3500m) on Walvis Ridge (SE Atlantic) across the EMET. Benthic δ18O values at both sites rose from ~49.7Ma on, becoming slightly higher at the shallower site than at the deeper site from ~44Ma on. Benthic δ13C values show a broad maximum at ~49-48Ma. Benthic foraminiferal assemblages at both sites are dominated by calcareous taxa, particularly Nuttallides truempyi, indicative of oligotrophic conditions. Large species of Bulimina, indicative of more food-rich conditions, were less rare at the shallower site, where benthic foraminiferal accumulation rates were generally higher. Specimens intermediate in morphology between N. truempyi (a cosmopolitan warm-water species which died out in the latest Eocene) and its extant, also cosmopolitan, cold-water descendant Nuttallides umbonifera (indicative of corrosive bottom waters), are present, as well as various Epistominella species, indicative of seasonal delivery of phytodetritus to the sea floor, and globally more common after the Eocene-Oligocene transition. These assemblages indicate that deep water environments started a gradual evolution from conditions typical for the warm early Eocene greenhouse to those typical for icehouse conditions by the end of the early Eocene. Characteristic early Eocene species such as Aragonia aragonensis and Quadrimorphina profunda persisted at least until 48Ma (the end of the studied interval) at the deeper site, whereas at the shallower site, they had their last appearances at ~49.7Ma, the time of increase in δ18O values, i.e., high latitude and deep-water cooling. The benthic foraminiferal transition towards assemblages typical for a glaciated world thus started close to the end of the early Eocene in the SE Atlantic, with the middle Eocene already representing a transitional world. The faunal changes in the SE Atlantic began earlier at upper abyssal than at lower abyssal depths. This suggests that a more stratified ocean started to develop in the SE Atlantic at the end of the EECO, possibly due to changes in source regions of intermediate water masses due to polar cooling and/or circulation changes around the Antarctic continent. © 2014 Elsevier B.V.


Gross D.,University of Leoben | Bechtel A.,University of Leoben | Harrington G.J.,University of Birmingham | Harrington G.J.,PetroStrat Ltd.
International Journal of Coal Geology | Year: 2015

This study reports on Cenozoic coal seamsrecovered at Integrated Ocean Drilling Program(IODP) Site C0020 during Expedition 337. IODP Site C0020 is located in a forearc basin formed by the subduction of the Pacific plate off Shimokita Peninsula (Japan). Hole C0020A penetrated 14 coal layers between 1825 and 2466 mbsf. Eleven of them were investigated within the frame of this paper. Investigated seams show a slight maturity increase with depth from lignite to sub-bituminous coal. In order to detect temporal changes in maceral and molecular composition and to relate them to changes in vegetation and depositional environment, macro- and micropetrographic data, bulk geochemical parameters, biomarker analysis, stable isotope geochemistry, and vitrinite reflectance measurements were performed. Resultswere also comparedwith palynological data obtained from 9 coal samples. Elevated sulfur contents and high ash yields occur in the upper seams (cores 14R to 18R)whereas lowsulfur contents and varying ash yields were determined for the lower coal seams (24R to 30R). The maceral composition and biomarker ratios of the uppermost seams argue for coal formation in a paralic environment and brackish, alkaline water conditions. In contrast, lignite samples from the lower part of unit III point to a limnic-fluviatile deposition. Conifers contributed significantly to peat formation in the uppermost seams (from cores 15R to 22R) and in the lowermost lignite seam. In all other samples, angiosperms are considered as the major peat-forming plants. The pollen and spore floras indicate rich angiosperm vegetation, however significant contributions from Pinaceae and Taxodiaceae are evident for all coals. Sporophytes have no dominant influence on the coal flora.Microbial activity in the peat is suggested for instance by higher concentrations of hop-17(21)-enewith increasing contents of hopanes or by lowd13C values of hop-17(21)-ene. The revealed changes in the environment during coal deposition highlight the importance of combined organic petrography, organic geochemistry and palynology to reconstruct palaeoenvironmental conditions. © 2015 Elsevier B.V.


Smith M.R.,University of Cambridge | Hughes G.M.G.,PetroStrat Ltd. | Vargas M.C.,Ecopetrol SA | de La Parra F.,Ecopetrol SA
Lethaia | Year: 2016

The problematic mollusc Wiwaxia is perhaps the most widely distributed non-mineralized Cambrian metazoan, but has only been reported from palaeotropical latitudes. Here, we describe mid-Cambrian (Drumian, c. 504 Ma) sclerites and possible tooth arrays from the northern Llanos Basin, Colombia, recovered from drilled ditch cuttings by palynological processing – demonstrating that pristine material and low-manipulation processing are not essential to the recovery of Small Carbonaceous Fossils. This, the first report of Wiwaxia from South America, substantially expands Wiwaxia's geographic range into the high palaeolatitudes. © 2015 Lethaia Foundation. Published by John Wiley & Sons Ltd


Phillips M.P.,University of Nebraska - Lincoln | Harwood D.M.,University of Nebraska - Lincoln | Harrington G.J.,University of Birmingham | Harrington G.J.,PetroStrat Ltd.
Marine Micropaleontology | Year: 2016

Integrated Ocean Drilling Program (IODP) Expedition 337 drilled a new core in 2012 that extended the coring depth of Hole C9001D at Site C9001 below the 647 meters below seafloor (mbsf) that was penetrated in 2006 during the Chikyu Shakedown Cruise CK06-06. Drilling operations at Site C0020 (formerly Site C9001), located 80 km off the Shimokita Peninsula of northeastern Honshu, Japan, penetrated Hole C0020A to a total depth of 2466 mbsf. IODP Exp. 337 sought to explore a deep hydrocarbon system and coalbeds that, prior to drilling, were estimated to be of Eocene age. Combined shipboard diatom and palynological analyses, however, revealed unexpectedly thick sections of Pliestocene and Miocene sediments, an approximately 12–15 million year hiatus at 1086.5 mud depth below sea floor (m MSF), and coalbeds younger than originally predicted. New biostratigraphic results from Hole C0020A indicate the target coalbed is Early Miocene. The age of the youngest sediments obtained in Hole C0020A is revised from Late Pliocene to Early Pleistocene, and the basal age of Hole C9001C is confirmed as Early Pleistocene. The age of the deepest sediments obtained at Site C0020 is Late Oligocene-Early Miocene. All new data are integrated with the overlying interval obtained from Holes C9001C and C9001D to produce a composite chronostratigraphic framework for Site C0020. © 2016 Elsevier B.V.


Hardas P.,PetroStrat Ltd. | Mutterlose J.,Ruhr University Bochum | Friedrich O.,Bundesanstalt fur Geowissenschaften und Rohstoffe | Friedrich O.,Goethe University Frankfurt | Erbacher J.,Bundesanstalt fur Geowissenschaften und Rohstoffe
Marine Micropaleontology | Year: 2012

In addition to Oceanic Anoxic Event 2 (OAE2), other perturbations of the carbon cycle occurred during the Cenomanian and Turonian, of which the Middle Cenomanian Event (MCE) is the most prominent one. In palaeoecological publications, however, this event is strongly underrepresented in contrast to the well-studied OAE2. In order to fill this gap, we have studied Early Cenomanian to Late Turonian calcareous nannofossil and benthic foraminiferal assemblages of Ocean Drilling Program Site 1260 at Demerara Rise (western equatorial North Atlantic), in order to decipher biotic changes throughout this interval and especially across the MCE. Our data show distinctive changes in the relative abundance of certain calcareous nannofossil taxa and a drastic decrease in benthic foraminiferal diversities and abundances associated with the MCE. In the lower part of the studied section and prior to the MCE, a mixed water-column with high nutrient availability in the upper photic zone is suggested based on very high relative abundances of the mesotrophic/eutrophic nannofossil species Biscutum constans. Around the MCE interval, certain nannofossil taxa (e.g., Rhagodiscus asper) show a distinctive decrease in relative abundance while others become more dominant. Taxa which increase in relative abundance after the MCE (e.g., Eprolithus floralis) are interpreted as either having favoured less eutrophic surface-waters or having inhabited deeper parts of the photic zone in a well stratified water-column. This interpretation is supported by published oxygen isotope and TEX86 data, which suggest increased water-column stratification starting with the MCE and lasting to the end of the Cenomanian stage, as a result of the implementation of a saline intermediate- to deep-water mass during this interval. Our study shows that the MCE was a significant biotic event in the Cenomanian/Turonian equatorial Atlantic, characterised by a lasting change of surface- and bottom-water ecosystems. © 2012 Elsevier B.V.


Alegret L.,University of Zaragoza | Ortiz S.,PetroStrat Ltd. | Arreguin-Rodriguez G.J.,University of Zaragoza | Monechi S.,University of Florence | And 2 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2016

The Latest Danian Event (LDE) or Top Chron C27n hyperthermal event has been identified in the Caravaca section (Southern Spain) by means of calcareous nannofossil biozones (Subzone NTp7b) and the recognition of a prominent, negative ~ 0.6 per mille carbon isotope excursion measured in benthic foraminiferal tests. This is the first time that this Danian hyperthermal event has been identified in a deep-water, middle to lower bathyal setting from the Western Tethyan realm. The analysis of benthic foraminiferal assemblages shows gradual changes in the assemblages prior to the onset of the LDE and an increase in food supply to the seafloor during the LDE, in agreement with results from shallower Southern Tethyan settings. The benthic assemblage changes across the LDE at Caravaca share some characteristics with other hyperthermal events, including the negative carbon isotope excursion, the increased abundance of buliminids, or the common occurrence of A. aragonensis, an opportunistic species that proliferated during other Paleogene hyperthermal events. In addition, the increased abundance of Nuttallides truempyi, a dissolution-resistant form that thrived during the Paleocene Eocene Thermal Maximum, and the abundance of calcareous infaunal morphogroups, which calcify in less carbonate-undersaturated pore waters, indicate slightly CaCO3-corrosive bottom waters during the LDE. Turnover of calcareous plankton across the LDE is similar to other sites globally distributed, including the evolution of photosymbiotic foraminiferal lineages and the radiation of the nannofossil “fasciculiths group”. The occurrence of innovative morphostructures (Diantholitha and Lithoptychius) towards the base of the LDE may indicate a more efficient biological pump. This hypothesis is supported by increased percentages of benthic infaunal morphogroups and a decrease in the abundance of oligotrophic species. A reworked interval has been identified immediately above the LDE. Higher up in the section, benthic and planktic assemblages from the post-LDE interval point to the recovery of the environmental conditions, including a decrease in the food supply to the seafloor. © 2016 Elsevier B.V.


Reggiani L.,PetroStrat Ltd | Reggiani L.,University of Perugia | Reggiani L.,University Claude Bernard Lyon 1 | Mattioli E.,University Claude Bernard Lyon 1 | Pittet B.,University Claude Bernard Lyon 1
Geobios | Year: 2010

Quantitative analyses of Pliensbachian calcareous nannofossils have been carried out on a proximal-distal transect in the Lusitanian Basin (Portugal). The studied sections Vale Venteiro near Tomar and Peniche represent proximal and distal environments with respect to the emerged land of the Iberian Meseta (to the East). The upper portion of the Vale das Fontes Fm (Davoei and Margaritatus ammonite Zones) is studied in both sections and correlated by means of ammonite and nannofossil integrated biostratigraphy. A careful analysis of the preservation state of nannofossils is performed. Preservation state is moderate to good in the two settings; changes in nannofossil assemblages are therefore considered as primary. Samples were analysed for nannofossil absolute and relative abundances, species diversity and wt%CaCO3. The analysis of calcareous nannofossils (absolute abundance, percentage, average abundance) shows changes in the community structure in space (i.e., from proximal to distal), and vertically within the water column. This pattern suggests a partitioning of habitats within the photic zone, and with respect to emerged lands. Proximal environments within the Lusitanian Basin were probably more eutrophic, because of the proximity of emerged lands to the East (Iberian Meseta). This was the source area for nutrients delivered into the basin by river transport. Distal environments were likely characterized by a greater water depth and by a deeper light penetration leading to a relatively more expanded photic zone. The assemblages recorded in the proximal setting exhibit high mean relative abundance of placolith-bearing coccolithophorids (Lotharingius spp., Biscutum spp. and Similiscutum spp.) and of Schizosphaerella spp., while distal assemblages are dominated by Crepidolithus crassus and Schizospharella spp. Crepidolithus crassus is interpreted as a deep-dweller coccolithophorid, inhabiting preferentially distal and deeper settings in the Lusitanian Basin. Placolith-bearing coccolithophorids were more abundant in proximal settings with respect to emerged lands, under relatively elevated trophic conditions. The probable calcareous dinocyst Schizospharella spp. proliferated in surface waters of both proximal and distal environments. © 2009 Elsevier Masson SAS. All rights reserved.


Grant
Agency: GTR | Branch: Innovate UK | Program: | Phase: Smart - Development of Prototype | Award Amount: 193.07K | Year: 2015

Exploitation of Shale gas requires the drilling of horizontal wells along the strata to be exploited with the location of the well within the strata having a big impact on the amount of gas or oil that can be extracted. A particular Shale deposit has a definite “sweet spot” in terms of productivity. Even a few feet up or down can have a significant impact. Directing a drill bit through strata is called “Geosteering” and requires a real-time analysis of the rock currently being drilled. Instrumentation mounted behind the drill bit can help but the only reliable process is to analyse the returned rock fragments. This is particularly important when an underground fault is encountered where the rock strata jumps vertically and the decision to go up or down to pick up the required strata again becomes crucial. Within the UK environmental concerns and high population density mean that wellsite locations will be far from optimal. Accurate geosteering to pick up specific strata up to 3 miles away will have a profound effect, both on the environmental impact and the economics of extraction. Unfortunately the relevant claystone is highly homogenous with very little differentiation across a significant vertical distance. Conventional Biostratigraphy, analysing the evolution of microscopic fossils to determine the age of the rock, cannot provide sufficient resolution for effective geo-steering due to the low rate of evolution versus sedimentation. PetroStrat, one of the world’s leading centres of expertise in biostratigraphy, has invented a new analytical methodology to enable homogenous claystone deposits, such as Bowland Shale, to be accurately geo-steered over large distances and through complex geological formations. Applying this technology across the Bowland Shale deposit the project will produce a highdefinition geo-steering “map” that will be used in conjunction with a trial geo-steered well to demonstrate the potential of the innovation.

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