scholarly journals Million-year-scale alternation of warm–humid and semi-arid periods as a mid-latitude climate mode in the Early Jurassic (late Sinemurian, Laurasian Seaway)

2021 ◽  
Vol 17 (4) ◽  
pp. 1547-1566
Author(s):  
Thomas Munier ◽  
Jean-François Deconinck ◽  
Pierre Pellenard ◽  
Stephen P. Hesselbo ◽  
James B. Riding ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Clay Mineral ◽  
Hydrological Cycle ◽  
Lower Jurassic ◽  
Climatic Conditions ◽  
Paris Basin ◽  
Burial Diagenesis ◽  
The North ◽  
Carbon Isotope Excursion ◽  
Semi Arid

Abstract. Clay mineral and stable isotope (C, O) data are reported from the upper Sinemurian (Lower Jurassic) of the Cardigan Bay Basin (Llanbedr–Mochras Farm borehole, northwestern Wales) and the Paris Basin (Montcornet borehole, northern France) to highlight the prevailing environmental and climatic conditions. In both basins, located at similar palaeolatitudes of 30–35∘ N, the clay mineral assemblages comprise chlorite, illite, illite–smectite mixed layers (R1 I-S), smectite, and kaolinite in various proportions. Because the influence of burial diagenesis and authigenesis is negligible in both boreholes, the clay minerals are interpreted to be derived from the erosion of the Caledonian and Variscan massifs, including their basement and pedogenic cover. In the Cardigan Bay Basin, the variations in the proportions of smectite and kaolinite are inversely related to each other through the entire upper Sinemurian. As in the succeeding Pliensbachian, the upper Sinemurian stratigraphic distribution reveals an alternation of kaolinite-rich intervals reflecting strong hydrolysing conditions and smectite-rich intervals indicating a semi-arid climate. Kaolinite is particularly abundant in the upper part of the obtusum zone and in the oxynotum zone, suggesting more intense hydrolysing conditions likely coeval with warm conditions responsible for an acceleration of the hydrological cycle. In the north of the Paris Basin, the succession is less continuous compared to the Cardigan Bay Basin site, as the oxynotum zone and the upper raricostatum zone are either absent or highly condensed. The clay assemblages are dominantly composed of illite and kaolinite without significant stratigraphic trends, but a smectite-rich interval identified in the obtusum zone is interpreted as a consequence of the emersion of the London–Brabant Massif following a lowering of sea level. Following a slight negative carbon isotope excursion at the obtusum–oxynotum zone transition, a long-term decrease in δ13Corg from the late oxynotum–early raricostatum zones is recorded in the two sites and may precede or partly include the negative carbon isotope excursion of the Sinemurian–Pliensbachian Boundary Event, which is recognised in most basins worldwide and interpreted to signify a late pulse of the Central Atlantic Magmatic Province volcanism.

scholarly journals Million-year-scale alternation of warm-humid and semi-arid periods as a mid-latitude climate mode in the Early Jurassic (Late Sinemurian, Laurasian Seaway)

2020 ◽  
Author(s):  
Thomas Munier ◽  
Jean-François Deconinck ◽  
Pierre Pellenard ◽  
Stephen P. Hesselbo ◽  
James B. Riding ◽  
...  
Keyword(s):  
Clay Mineral ◽  
Hydrological Cycle ◽  
Lower Jurassic ◽  
Climatic Conditions ◽  
Paris Basin ◽  
Burial Diagenesis ◽  
The North ◽  
Central Atlantic Magmatic Province ◽  
Central Atlantic ◽  
Semi Arid

Abstract. High resolution clay mineral and stable isotope (C, O) data are reported from the upper Sinemurian (Lower Jurassic) of the Cardigan Bay Basin (Llanbedr [Mochras Farm] borehole, northwest Wales) and the Paris Basin (Montcornet borehole, northern France) to highlight the prevailing environmental and climatic conditions. In both basins, located at similar palaeolatitudes of 30–35° N, the clay mineral assemblages comprise chlorite, illite, illite-smectite mixed-layers (R1 I-S), smectite and kaolinite in various proportions. Because the influence of burial diagenesis and authigenesis is negligible in both boreholes, the clay minerals are interpreted to be derived from the erosion of the Caledonian and Variscan massifs, including their basement and pedogenic cover. In the Cardigan Bay Basin, the variations in the proportions of smectite and kaolinite are inversely related to each other over the entire upper Sinemurian succession. As in the Pliensbachian, the stratigraphical distribution reveals an alternation of kaolinite-rich intervals reflecting strong hydrolysing conditions, and smectite-rich intervals indicating a semi-arid climate. Kaolinite is particularly abundant in the upper part of the obtusum Zone and in the oxynotum Zone, suggesting more intense hydrolysing conditions likely coeval with warm conditions responsible for an acceleration of the hydrological cycle. This interval is also marked by a negative excursion of δ13Ccarb and δ18Ocarb, which may confirm a warmer palaeoclimate, although these excursions may be exaggerated or overprinted by the carbonate diagenesis. In the north of the Paris Basin, the stratigraphical succession is much thinner compared to the Cardigan Bay Basin site, and the oxynotum Zone is either absent or highly condensed. The clay assemblages are dominantly composed of illite and kaolinite without significant stratigraphical trends, but a smectite-rich interval identified in the obtusum Zone is interpreted as a consequence of the emersion of the London-Brabant Massif following a lowering of sea-level. A long-term decrease of δ13Corg from the late oxynotum/early raricostatum zones is also recorded in the two sites and may precede or partly include the negative carbon-isotope excursion of the Sinemurian/Pliensbachian Boundary Event, recognised in most basins worldwide, and interpreted as a late pulse of the Central Atlantic Magmatic Province volcanism.

scholarly journals Carbon isotope (δ<sup>13</sup>C) excursions suggest times of major methane release during the last 14 kyr in Fram Strait, the deep-water gateway to the Arctic

2015 ◽  
Vol 11 (4) ◽  
pp. 669-685 ◽  
Author(s):  
C. Consolaro ◽  
T. L. Rasmussen ◽  
G. Panieri ◽  
J. Mienert ◽  
S. Bünz ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Carbon Isotope ◽  
Deep Water ◽  
Planktonic Foraminifera ◽  
Sediment Supply ◽  
The Arctic ◽  
Fram Strait ◽  
The North ◽  
Carbon Isotope Excursion

Abstract. We present results from a sediment core collected from a pockmark field on the Vestnesa Ridge (~ 80° N) in the eastern Fram Strait. This is the only deep-water gateway to the Arctic, and one of the northernmost marine gas hydrate provinces in the world. Eight 14C AMS dates reveal a detailed chronology for the last 14 ka BP. The δ 13C record measured on the benthonic foraminiferal species Cassidulina neoteretis shows two distinct intervals with negative values termed carbon isotope excursion (CIE I and CIE II, respectively). The values were as low as −4.37‰ in CIE I, correlating with the Bølling–Allerød interstadials, and as low as −3.41‰ in CIE II, correlating with the early Holocene. In the Bølling–Allerød interstadials, the planktonic foraminifera also show negative values, probably indicating secondary methane-derived authigenic precipitation affecting the foraminiferal shells. After a cleaning procedure designed to remove authigenic carbonate coatings on benthonic foraminiferal tests from this event, the 13C values are still negative (as low as −2.75‰). The CIE I and CIE II occurred during periods of ocean warming, sea-level rise and increased concentrations of methane (CH4) in the atmosphere. CIEs with similar timing have been reported from other areas in the North Atlantic, suggesting a regional event. The trigger mechanisms for such regional events remain to be determined. We speculate that sea-level rise and seabed loading due to high sediment supply in combination with increased seismic activity as a result of rapid deglaciation may have triggered the escape of significant amounts of methane to the seafloor and the water column above.

Where should the Global Stratotype Section and Point (GSSP) for the Paleocene/Eocene boundary be located?

2000 ◽  
Vol 171 (4) ◽  
pp. 461-476 ◽  
Author(s):  
Marie-Pierre Aubry
Keyword(s):  
Carbon Isotope ◽  
Critical Points ◽  
Working Group ◽  
Historical Review ◽  
International Commission ◽  
Paris Basin ◽  
Carbon Isotope Excursion ◽  
Stratotype Section ◽  
Definition Of ◽  
Selection Of

Abstract The Working Group (WG) on the Paleocene/Eocene (P/E) boundary will soon have to submit a formal proposal regarding the selection of a GSSP for the boundary. Before it proceeds, a number of critical points must be considered. First, there has been dual definition of the Paleocene/Eocene boundary so that even today the boundary is placed at two different lithostratigraphic horizons by marine and vertebrate paleontologists. The former use the base of the Ypresian Stage = Mont Heribu Member in the Belgium Basin whereas the latter use the Conglomerat de Meudon believed until recently to lie at the base of the Sparnacian Argile plastique of the Paris Basin. A historical review of the definitions of the terms that have become accepted as standard chronostratigraphic units help to explain how this dual definition arose and to show that the definition accepted by most vertebrate paleontologists is spurious. The current placement of the Paleocene/Eocene boundary, i.e., defined by the base of Ypresian Stage (Ieper Clay), conforms to the definition of the Paleocene by Schimper in 1874. Second, the WG must determine whose basic chronostratigraphic procedures to follow. There has been in recent years a profound shift in chronostratigraphic procedures so that the fundamental principles recognized by the International Subcommission on Stratigraphic classification [ISSC, Hedberg, Ed, 1976; Salvador, Ed., 1994] are difficult to reconcile with the rules published by the International Commission on Stratigraphy (ICS) in recent years, based on the precept that "correlation precedes definition". For this reason the WG finds itself in a dilemma, and must weigh the risks associated with the attractive solution that would consist in defining the P/E boundary by a lithostratigraphic level where the late Paleocene carbon isotope excursion (CIE) is recorded. Four possible options that may satisfy Hedberg's principle of chronostratigraphy and/or the need for recognizing globally the Paleocene/Eocene boundary are presented. Whichever option is followed, it is important to remember that chronostratigraphy must remain objective and as arbitrary as possible, and thus independent of any aspect of Earth history, either paleobiologic, tectonic or climatic. In addition, in making a proposal for the definition of the P/E boundary, the WG must ensure that its choice will not contribute to a destabilisation of the current chronostratigraphic framework.

Expression of the Early Toarcian negative carbon-isotope excursion in separated carbonate microfractions (Jurassic, Paris Basin)

2009 ◽  
Vol 277 (1-2) ◽  
pp. 194-203 ◽  
Author(s):  
Michaël Hermoso ◽  
Laurence Le Callonnec ◽  
Fabrice Minoletti ◽  
Maurice Renard ◽  
Stephen P. Hesselbo
Keyword(s):  
Carbon Isotope ◽  
Paris Basin ◽  
Carbon Isotope Excursion

scholarly journals New Chronostratigraphic Constraints on the Lower Jurassic Pliensbachian–Toarcian Boundary at Chacay Melehue (Neuquén Basin, Argentina)

2021 ◽  
Author(s):  
Aisha H. Al-Suwaidi ◽  
Micha Ruhl ◽  
Hugh C. Jenkyns ◽  
Susana E. Damborenea ◽  
Miguel O. Manceñido ◽  
...  
Keyword(s):  
High Resolution ◽  
Carbon Isotope ◽  
Volcanic Ash ◽  
Lower Jurassic ◽  
Zircon Geochronology ◽  
Organic Carbon Isotope ◽  
Carbon Isotope Excursion ◽  
Isotope Record ◽  
Age Model ◽  
Zonal Boundary

Abstract The Pliensbachian–Toarcian boundary interval is characterized by a ~3‰ negative carbon-isotope excursion (CIE) in organic and inorganic marine and terrestrial archives from sections in Europe, such as Peniche (Portugal) and Hawsker Bottoms, Yorkshire (UK). A new high-resolution organic-carbon isotope record, illustrating the same chemostratigraphic feature, is presented from the Southern Hemisphere Arroyo Chacay Melehue section, Chos Malal, Argentina, corroborating the global significance of this disturbance to the carbon cycle. The negative carbon-isotope excursion, mercury and organic-matter enrichment is accompanied by high-resolution ammonite and nannofossil biostratigraphy together with U-Pb CA-ID-TIMS geochronology derived from intercalated volcanic ash beds. A new age of ~183.71 ± 0.40/-0.51 Ma for the Pliensbachian–Toarcian boundary, and 182.77 +0.11/-0.21 for the tenuicostatum–serpentinum zonal boundary, is assigned based on high-precision U-Pb zircon geochronology and a Bayesian Markov chain Monte Carlo (MCMC) stratigraphic age model.

scholarly journals Late Cretaceous (late Campanian–Maastrichtian) sea-surface temperature record of the Boreal Chalk Sea

2016 ◽  
Vol 12 (2) ◽  
pp. 429-438 ◽  
Author(s):  
Nicolas Thibault ◽  
Rikke Harlou ◽  
Niels H. Schovsbo ◽  
Lars Stemmerik ◽  
Finn Surlyk
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Carbon Isotope ◽  
Sea Surface ◽  
Temperature Record ◽  
Climatic Fluctuations ◽  
The North ◽  
Carbon Isotope Excursion ◽  
First Time

Abstract. The last 8 Myr of the Cretaceous greenhouse interval were characterized by a progressive global cooling with superimposed cool/warm fluctuations. The mechanisms responsible for these climatic fluctuations remain a source of debate that can only be resolved through multi-disciplinary studies and better time constraints. For the first time, we present a record of very high-resolution (ca. 4.5 kyr) sea-surface temperature (SST) changes from the Boreal epicontinental Chalk Sea (Stevns-1 core, Denmark), tied to an astronomical timescale of the late Campanian–Maastrichtian (74 to 66 Ma). Well-preserved bulk stable isotope trends and calcareous nannofossil palaeoecological patterns from the fully cored Stevns-1 borehole show marked changes in SSTs. These variations correlate with deep-water records of climate change from the tropical South Atlantic and Pacific oceans but differ greatly from the climate variations of the North Atlantic. We demonstrate that the onset and end of the early Maastrichtian cooling and of the large negative Campanian–Maastrichtian boundary carbon isotope excursion are coincident in the Chalk Sea. The direct link between SSTs and δ13C variations in the Chalk Sea reassesses long-term glacio-eustasy as the potential driver of carbon isotope and climatic variations in the Maastrichtian.

Diagenetic chlorite formation in some Mesozoic shales from the Sleipner area of the North Sea

Clay Minerals ◽  
1985 ◽  
Vol 20 (1) ◽  
pp. 69-79 ◽  
Author(s):  
A. Hurst
Keyword(s):  
Clay Mineral ◽  
North Sea ◽  
Clay Mineralogy ◽  
Reliable Indicator ◽  
Burial Diagenesis ◽  
The North ◽  
The North Sea ◽  
Temperature Controlled ◽  
Mineral Transformations

AbstractDiagenetic chlorite is forming as a result of temperature-controlled burial diagenesis in shales from the Sleipner area of the North Sea. Accompanying chlorite diagenesis, kaolinite and illite-smectite decrease in abundance, and illite increases in abundance. These clay mineral transformations occur between 122–126°C at temperatures higher than normally expected for chlorite diagenesis. Kaolinite and ordered illite-smectite are largely unaffected by diagenesis below 100°C. It is proposed that chlorite diagenesis is thus delayed due to the absence of a source of ions resulting from smectite decomposition. Clay mineralogy is of no lithostratigraphic use in the Jurassic sediments of the Sleipner area. However, the zone of chlorite diagenesis is a reliable indicator of maximum burial temperature.

scholarly journals Spatiotemporal Changes of Reference Evapotranspiration in Mongolia during 1980–2006

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
Wenjun Yu ◽  
Tonghua Wu ◽  
Weizhen Wang ◽  
Ren Li ◽  
Tianye Wang ◽  
...  
Keyword(s):  
Hydrological Cycle ◽  
Reference Evapotranspiration ◽  
Kendall Test ◽  
Climatic Conditions ◽  
Meteorological Variables ◽  
The South ◽  
Sparse Vegetation ◽  
The North ◽  
The Mean ◽  
Aridity Indices

Reference evapotranspiration (RET) plays an important role in the terrestrial hydrological cycle. Applying the Penman-Monteith method, the RET over Mongolia was estimated from 1980 to 2006. The changing trends and magnitude of RET were detected by the Mann-Kendall test and Theil-Sen’s slope methods. Meanwhile, aridity indices were estimated using two different indices. The impacts of meteorological variables on RET were assessed through sensitive analysis by comparing the resulting RETs from artificially disturbed meteorological variables. The results indicated that the RET for 16 stations in Mongolia showed an increasing trend, particularly in the center and south. The calculated RET was higher than precipitation, which means severe droughts in Mongolia. The spatial patterns of RET are significantly influenced by climatic conditions as well as characteristics of the underlying surface (e.g., elevation and vegetation). The mean annual RET decreased from the south to the north, owing to sparse vegetation in the south of Mongolia. The sensitivity analysis revealed that the changes of RET were strongly affected by air temperature and relative humidity.

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