scholarly journals A rapid sedimentary response to the Paleocene-Eocene Thermal Maximum hydrological change: new data from alluvial units of the Tremp-Graus Basin (Spanish Pyrenees)

2021 ◽  
Author(s):  
Victoriano Pujalte ◽  
Birger Schmitz ◽  
Aitor Payros
Keyword(s):  
Source Area ◽  
Depositional Environments ◽  
Sedimentation Rates ◽  
Hydrological Change ◽  
The Core ◽  
Carbon Isotope Excursion ◽  
Thermal Maximum ◽  
Spanish Pyrenees ◽  
Terrestrial Sediments ◽  
Sedimentary System

A massive emission of light carbon about 56 Ma ago, recorded in marine and terrestrial sediments by a negative carbon isotope excursion (CIE), caused a short-lived (~170 kyr) global warming event known as the Paleocene–Eocene Thermal Maximum (PETM). The core of this event is represented in the south Pyrenean Tremp-Graus Basin by two successive alluvial units, the Claret Conglomerate (CC) and the Yellowish Soils, which represent laterally juxtaposed depositional environments. It is generally agreed that these units record a dramatic increase in seasonal rain and an increased intra-annual humidity gradient during the PETM, but the timing of the sedimentary response to the hydrological change is a matter of debate. Some authors maintain that the CC was developed during the early, most intense phase of the carbon emission, others that its formation lagged by 16.5 ± 7.5 kyr behind the onset of the PETM. The latter claim was mainly based on the assumption that in two sections of this basin, Claret and Tendrui, the onset of the CIE occurs 3 and 8 m below the base of the CC, respectively. Here we show that in the zone between these two sections the CC is missing and the Yellowish Soil unit rests directly and conformably on the underlying deposits. New d13Corg data from this zone provide sound evidence that the onset of the CIE is situated just ~1 m below the Yellowish Soils. The CC erosional base cuts down deeper than this figure, rendering it highly unlikely the preservation of the CIE onset below it. A tentative estimate based on sedimentation rates indicates that ~3.8 kyr, or less, may have elapsed from the onset of the CIE to the arrival of PETM alluvium into the Claret-Tendrui study area, about a third of the lowest estimate of previous authors. Since the study area was situated about 15 km from the source area, our new estimate supports a rapid response of the sedimentary system to the hydrological change at the onset of the PETM.

Calcium isotope composition of Morozovella over the late Paleocene–early Eocene

Geology ◽  
2021 ◽  
Author(s):  
Gabriella D. Kitch ◽  
Andrew D. Jacobson ◽  
Dustin T. Harper ◽  
Matthew T. Hurtgen ◽  
Bradley B. Sageman ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Calcium Isotope ◽  
Ocean Drilling Program ◽  
Ocean Drilling ◽  
Carbonate Ion ◽  
Kinetic Isotope ◽  
Carbon Isotope Excursion ◽  
Thermal Maximum ◽  
Igneous Province ◽  
North Atlantic Igneous Province

Ocean acidification (OA) during the Paleocene-Eocene thermal maximum (PETM) likely caused a biocalcification crisis. The calcium isotope composition (δ44/40Ca) of primary carbonate producers may be sensitive to OA. To test this hypothesis, we constructed the first high-resolution, high-precision planktic foraminiferal δ44/40Ca records before and across the PETM. The records employ specimens of Morozovella spp. collected from Ocean Drilling Program Sites 1209 (Shatsky Rise, Pacific Ocean) and 1263 (Walvis Ridge, Atlantic Ocean). At Site 1209, δ44/40Ca values start at –1.33‰ during the Upper Paleocene and increase to a peak of –1.15‰ immediately before the negative carbon isotope excursion (CIE) that marks the PETM onset. Values remain elevated through the PETM interval and decrease into the earliest Eocene. A shorter-term record for Site 1263 shows a similar trend, although δ44/40Ca values are on average 0.22‰ lower and decrease shortly after the CIE onset. The trends support neither diagenetic overprinting, authigenic carbonate additions, nor changes in the δ44/40Ca value of seawater. Rather, they are consistent with a kinetic isotope effect, whereby calcite δ44/40Ca values inversely correlate with precipitation rate. Geologically rapid Ca isotope shifts appear to reflect the response of Morozovella to globally forced changes in the local carbonate geochemistry of seawater. All data combined suggest that the PETM-OA event occurred near the peak of a gradual reduction in seawater carbonate ion concentrations during a time of elevated atmospheric pCO2, potentially driven by North Atlantic igneous province emplacement.

scholarly journals Resultantes geo-hidroecológicas do ciclo cafeeiro (1780-1880) no médio vale do rio Paraíba do Sul: uma análise quali-quantitativa

1996 ◽  
Vol 19 ◽  
pp. 61-78
Author(s):  
Marcelo Eduardo Dantas ◽  
Ana Luiza Coelho Netto
Keyword(s):  
Environmental Impact ◽  
Economic Activity ◽  
Source Area ◽  
River Valley ◽  
Historical Documents ◽  
Sedimentation Rates ◽  
Economic Cycle ◽  
Drought Period ◽  
Radiocarbon Dates ◽  
Valley Fills

The coffee cycle represented a period of intense morphodynamic activity, proceeding by a general deforestation. On the Paraíba do Sul Middle Valley, this economic cycle lasted 100 years aproximately (1780-1880). Historical documents, radiocarbon dates and volumetric measurements of the valley fills correlated from the coffee time, have provided informations on the environmental impact, particularly associated with climatic and hidro-erosive processes both on the hillslopes and fluvial domains. Deforestation introduced a drought period up to 6 months and also to an increasing frequency of intense rainstorms, particularly in the summer. Along the Piracema river valley, sedimentation rates attained about 70.000m³km/year. Transfering this volume to the source-area on the hillslopes, it gives an estimate relief downwearing around 7,5 cm depth, resulting on the removal of the organic rich A horizon and showing so, the catastrophic effect of this economic activity, resulting in an extremely wasted degraded landscape.

Sedimentary fades, depositional environments, and faunal associations of the lower Llandovery (Silurian) Beechill Cove Formation, Arisaig, Nova Scotia

1983 ◽  
Vol 20 (12) ◽  
pp. 1761-1779 ◽  
Author(s):  
R. K. Pickerill ◽  
J. M. Hurst
Keyword(s):  
Depositional Environments ◽  
Low Energy ◽  
Sedimentation Rates ◽  
Storm Activity ◽  
Distributional Patterns ◽  
Low Diversity ◽  
Energy Environment ◽  
Shallow Subtidal ◽  
Oxygen Minimum ◽  
Mudstone Facies

Six facies are recognised in the Beechill Cove Formation. These are: (1) conglomerate facies deposited as a transgressive beach lag; (2) red shale facies deposited in shoreface environments; (3) mottled mudstone facies; extensively bioturbated sediments indicative of shallow subtidal areas influenced by low sedimentation rates; (4) regular layered facies; shelf turbidites generated by storm activity and superimposed on quiescent subtidal environments; (5) lenticular facies, including a thinner bedded more persistent and a thicker bedded lenticular subfacies, induced by storm activity and deposited in shallow subtidal environments; and (6) laminated shale facies produced by sediment fallout from suspension in a low-energy environment where the oxygen, minimum layer intersected the sediment–water interface. Three faunal associations occur, which have distinct distributional patterns. The Lingula clintoni association, which is characterized by L. clintoni in life position and a moderately diverse but abundant trace-fossil assemblage, is restricted to the mottled mudstone facies. The Leptostrophia beechillensis association, a transported residue, is dominated by brachiopods and restricted to the regular layered facies. The low-diversity Dalmanella primitiva association is transported and restricted to the lenticular facies. No faunas are known from the conglomerate or laminated shale facies, and only rare trace fossils occur in the red shale facies.

scholarly journals Late Paleocene event chronology; unconformities, not diachrony

2000 ◽  
Vol 171 (3) ◽  
pp. 367-378 ◽  
Author(s):  
Marie-Pierre Aubry ◽  
Benjamin S. Cramer ◽  
Kenneth G. Miller ◽  
James D. Wright ◽  
Dennis V. Kent ◽  
...  
Keyword(s):  
Planktonic Foraminifera ◽  
Calcareous Nannoplankton ◽  
Lower Eocene ◽  
Late Paleocene ◽  
Relative Chronology ◽  
Carbon Isotope Excursion ◽  
Thermal Maximum ◽  
Unequivocal Identification ◽  
Upper Paleocene ◽  
Reference Section

Abstract The chronology of the events associated with the late Paleocene thermal maximum (LPTM, Chron C24r) has been established through the construction of a composite reference section that involved chemomagnetobiostratigraphic correlations and assumed minimum diachrony of biostratigraphic events. On this basis, discrepancies between correlations in different sections were explained by inferred unconformities. However, diachrony between distant sections cannot be ruled out. We report here on two geographically close sections drilled onshore New Jersey that yield different records of chemomagnetobiostratigraphic correlations in the interval representing Chron C24r. Because of their proximity ( approximately 40 km apart), diachrony of biostratigraphic events between the two sections can be ruled out. In contrast, the marked lithologic disconformities in the sections explain well the different records of events. We thus conclude that the current relative chronology for Chron C24r is firmly based and that the upper Paleocene-lower Eocene stratigraphic record yields multiple unconformities, with Subzone NP9b rarely sampled. We examine the implications that undeciphered unconformities may have on the identification of proxies for paleoceanographic reconstruction, in particular with regard to the identification of the carbon isotope excursion (CIE) that reflects a dramatic latest Paleocene disturbance of the carbon cycle. We propose biostratigraphic means (short-lived calcareous nannoplankton and planktonic foraminifera taxa) that permit the unequivocal identification of the CIE not only in the oceanic realm but also in neritic settings.

Stratigraphic and sedimentological aspects of the worldwide distribution of Apectodinium in Paleocene/Eocene Thermal Maximum deposits

2021 ◽  
pp. SP511-2020-46
Author(s):  
Christopher N. Denison
Keyword(s):  
Global Warming ◽  
Sea Level ◽  
Environmental Changes ◽  
Calcareous Nannofossil ◽  
Shallow Marine ◽  
Worldwide Distribution ◽  
Carbon Isotope Excursion ◽  
Thermal Maximum ◽  
Taxonomic Changes ◽  
Data Gap

AbstractThe Paleocene/Eocene Thermal Maximum (PETM) is characterized by pronounced global warming and associated environmental changes. In the more-or-less two decades since prior regional syntheses of Apectodinium distribution at the PETM, extensive biological and geochemical datasets have elucidated the effect of rising world temperatures on climate and the biome. A Carbon Isotope Excursion (CIE) that marks the Paleocene/Eocene Boundary (PEB) is associated with an acme of marine dinocysts of the genus Apectodinium in many locations. Distinctive foraminiferal and calcareous nannofossil populations may also be present.For this up-dated, dinocyst-oriented view of the PETM, data from worldwide locations have been evaluated with an emphasis on stratigraphic and sedimentological context. What has emerged is that a change in lithology is common, often to a distinctive siltstone or claystone unit, which contrasts with underlying and overlying lithotypes. This change, present in shallow marine/coastal settings and in deepwater turbidite deposits, is attributed to radical modifications of precipitation and erosional processes. An abrupt boundary carries the implication that some time (of unknowable duration) is potentially missing, which then requires caution in the interpretation of the pacing of events in relation to that boundary. In most instances an ‘abrupt’ or ‘rapid’ CIE onset can be attributed to a data gap at a hiatus, particularly in shallow shelf settings where transgression resulted from sea-level rise associated with the PETM. Truly gradational lower boundaries of the PETM interval are quite unusual, and if present, are poorly known so far. Gradational upper boundaries are more common, but erosional upper boundaries have been reported.Taxonomic changes have been made to clarify identification issues that have adversely impacted some biostratigraphic interpretations. Apectodinium hyperacanthum has been retained in Wetzeliella, its original genus. The majority of specimens previously assigned to Apectodinium hyperacanthum or Wetzeliella (Apectodinium) hyperacanthum have been re-assigned to an informal species, Apectodinium sp. 1. Dracodinium astra has been retained in its original genus as Wetzeliella astra, and is emended.

Submarine topographic control on distribution of supercritical-flow deposits in lobe and related environments, middle Eocene, Jaca Basin, Spanish Pyrenees

2020 ◽  
Vol 90 (9) ◽  
pp. 1222-1243
Author(s):  
Pauline H. Cornard ◽  
Kevin T. Pickering
Keyword(s):  
Grain Size ◽  
Distal Part ◽  
Middle Eocene ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Seafloor Topography ◽  
Submarine Channels ◽  
Supercritical Flow ◽  
Spanish Pyrenees ◽  
Bed Thickness

ABSTRACT Submarine lobe and related deposits are amongst the largest discrete sandbodies on Earth, and can be significant hydrocarbon reservoirs. In outcrop and core-based studies, tools such as analysis of bed-thickness and grain-size distributions have been used to improve the understanding of the composition and architecture of such sandbodies. Analysis of sediment-gravity-flow (SGF) processes have also proved to be a useful tool in understanding the evolution of submarine lobes. In this paper, based on outcrop studies of submarine lobe and related deposits in the middle Eocene Jaca Basin, Spanish Pyrenees, a revised interpretation of the depositional environments of the lobe and related deposits and a new model for their architectural evolution is presented. This model is based on an analysis of bed-thickness, grain-size distribution, and a qualitative and quantitative study of the distribution of supercritical-flow deposits (SFDs) in these environments. The interpretation of lobe and related environments is mainly based on sandstone content and the distribution of sedimentary facies. The main supercritical-flow sedimentary structures recognized in the Jaca Basin, are unstable and stable antidunes, upper plane beds and backset-laminated beds. This study demonstrates that seafloor topography, strongly controlled by both syndepositional tectonics and the accumulation of mass-transport complexes, likely exerted a significant influence on lobe architecture and the distribution of SFDs. Local increase in bed thickness, together with a progressive decrease in grain size and little variation in the proportion of SFDs in proximal-to-distal and axial-to-lateral directions, can be explained by: i) an increase in basin confinement of the distal part of the Jaca Basin due to tectonically induced narrowing, ii) enhanced local lateral confinement due, at least in part, to “carbonate megaturbidites” present in the distal part of the Jaca Basin and creating topography. Thus, basin confinement is introduced as a new parameter playing a role on flow criticality. There is a decreasing proportion of SFDs between the submarine channels and canyons of the Ainsa Basin and the submarine lobes of the Jaca Basin, the last basin being the focus of this paper. This confirms previous studies showing that channel confinement and slope gradient likely played an important role in flow criticality.

scholarly journals Characterization of the gamma flux in a tangential channel of the CENM TRIGA MARK II research reactor

2020 ◽  
Vol 225 ◽  
pp. 04030
Author(s):  
A. Gruel ◽  
D. Fourmentel ◽  
C. El Younoussi ◽  
B. El Bakkari ◽  
Y. Boulaich ◽  
...  
Keyword(s):  
Steady State ◽  
Nuclear Data ◽  
Neutron Field ◽  
Photon Propagation ◽  
The Core ◽  
Thermal Maximum ◽  
Gamma Field ◽  
Triga Mark Ii ◽  
Gamma Flux

The CNESTEN (National Center for Energy Sciences and Nuclear Technology, Morocco) operates a TRIGA Mark II reactor, which can reach a thermal maximum power at steady state of 2 MW. In reactors devoted to research and experiments, it is mandatory to characterize the neutron and photon fields in the irradiation positions. Together with a computational model of the core, it ensures the ability to reach the requested uncertainties when performing experiments, such as detectors testing, irradiation for hardening or nuclear data measurements. The neutron field of different irradiation positions has been characterized by dosimetry techniques and compared to the MCNP full model of the reactor. Preliminary photon propagation calculations are also performed with this model, but up to now, no experimental validation of the results exists. The aim of the newly set collaboration between CEA and CNESTEN is to characterize the gamma field of these positions. The first position investigated is the part of the NB1 tangential channel closest to the core. Among gamma measurements techniques, and according to the constraints arising from using this channel, it was chosen to use thermos- and optically stimulated luminescent detectors. This paper presents the experiments carried out in September 2018 as well as their results. Three detectors types were used: TLD400 (CaF2:Mn), TLD700 (7LiF:Mg,Ti) and OSLD (Al2O3:C). Measurements were performed in several steps: background measurements, transient measurements (divergence phase + SCRAM), and irradiation at steady state. In the end, these measurements will provide a dose as well as a gamma flux value for this position.

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