2010 IGCP 580-Guilin, China

8/12/2019 2010 IGCP 580-Guilin, China

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2010 IGCP 580 Meeting

Applications of Magnetic Susceptibility

on Paleozoic Rocks

Meeting Programme and Abstracts

28thNovember 4

thDecember 2010, Guilin, China


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Locations of Airport, Railway Station and Hotel

Guilin LiangjiangInternational Airport

Guilin Park Hotel

Guilin Park Hotel

Guilin Railway Station


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Co-Chairs

Dr. Prof. Daizhao Chen, Institute of Geology and Geophysics,

Chinese Academy of Sciences, China

E-mail address: [email protected]

Dr. Anne-Christine da Silva, Department of Geological Sciences,

University of Liege, Belgium

E-mail address:[email protected]

Sponsors

-Unesco-IUGS-IGCP Committee

-National Natural Science Foundation of China (NSFC)

-Chinese Academy of Sciences (CAS)

-Institute of Geology and Geophysics, CAS


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MEETING PROGRAMME

9:00-18:00 On-site Registration Guilin Park Hotel

18:30-20:30 Ice Breaker and Dinner Guilin Park Hotel

8:30-8:40

Daizhao Chen

Anne-Christine da Silva Opening remarks

8:40-9:00 Anne-Christine da Silva

Magnetic susceptibility evolution in Devonian Belgian carbonates:

characterisation of magnetic mineralogy and discussion on the origin and

the evolution of the magnetic signal.

9:00-9:20 Jindrich Hladil

Complex pathways of iron uptake in stromatoporoid skeletons: variability

mapped by magnetic susceptibility

9:20-9:40 Shihong Zhang

Magnetic susceptibility variations of the laminated carbonates of the

Ediacaran Doushantuo Formation in South China and their stratigraphic

implications

9:40-10:00 Katarzyna Sobien

Petromagnetic indications of environmental changes in the Devonian

Carboniferous boundary section in Poland (Pomerania region)

10:00-10:30

10:30-10:50 Frdric Boulvain

MS of Frasnian reefs and mounds from Eastern Belgium

Poster: MS of Lower carboniferous sections (Tournaisian, Belgium)

10:50-11:10 Prasannakumar Kaimal

Upper Permian Sedimentary Environments of Indian Gondwana Basins:

Evidences from Magnetic Anisotropy

11:10-11:30 Leona Koptikova

The effect of different acid dissolution methods on magnetic properties of

insoluble residues of limestones

11:30-11:50 Estelle Petitclerc

Rock magnetism, sedimentology, gamma-ray logging, reefal and peri-

reefal fauna in the Mont dHaurs and Fromelennes formations (Late

Givetian) at Cul dHouille section (Flohimont, France)

12:00-13:00

13:30-13:50 Xavier Devleeschouwer

Rock magnetism and sedimentology at the Hanonet/Trois-Fontaines

transition (base of the Givetian, Belgium) in the Fondry des Chiens and

Mont dHaurs sections

13:50-14:10 Jifeng Yu

Recognition of Milankovitch cyclicity in Magnetic Susceptibility Data with

Wavelet Transform

14:10-14:30 Petr Schnabl

Local remagnetization of sedimentary and volcanosedimentary rocks

from Barrandian area (Prague Synform, Bohemian Massif)

14:30-15:00

15:00-15:20 Michael Whalen

Differential geochemical response during the lower and upper Kellwasser

events, western Canada: Implications for global change

15:20-15:40 Ondrej Bbek

Non-magnetic proxies of pedogenesis related to Chinese and

Siberian/Alaskan model of magnetic alteration of loess; examples from

Czech Republic and southern Siberia

15:40-16:00 Daizhao Chen

Multiple isotopic constraints on the vast environmental changes during

the Frasnian-Famennian transition of Late Devonian

16:00-16:10 Jindrich Hladil Statement of next meeting16:10-17:30

18:30-20:30

8:30

18:30

8:00

18:30

8:30

18:30

Tuesday, November 30th

Field excursions

Dinner

Dinner

Convener: Anne-Christine da Silva

Convener: Jindrich Hladil

Tea/Coffee Break and Meeting Photograph

Saturday, November 27th

Sunday, November 28th

Convener: Frdric Boulvain

Dinner

Lunch Break

Tea/Coffee Break

Social dinner

Team work on the field

Convener: Michael Whalen

Poster Session

Monday, November 29th

Field excursions

Wednesday-Saturday, December 1st-4

th


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ABSTRACT VOLUME

Oral and Poster Contributions in presentation order


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Abstract-1

Magnetic susceptibility evolution in Devonian Belgian carbonates:

characterisation of magnetic mineralogy and discussion on the origin

and the evolution of the magnetic signal.

A-C. da Silva1, M J. Dekkers

2, C. Mabilleand

1, F. Boulvain

1

1 Ptrologie sdimentaire, B20, Boulevard du Rectorat, 15, Universit de Lige, 4000

Lige,Belgium ([email protected])

2 Paleomagnetic Laboratory, Fort Hoofddijk, Department of Earth Sciences, Utrecht University,

Budapestlaan 17, 3584 CD Utrecht, Netherlands ([email protected])

The magnetic susceptibility (MS) signal in the Devonian from Belgium shows a strongcorrelation with facies evolution (da Silva and Boulvain, 2006); a clear link between

sedimentary cycles is observed (fourth and third order), each regressive trend

corresponding to a MS peak on the MS evolution curve. Furthermore, a strong

relationship between mean MS values and microfacies occurs, with increasing mean

MS related to proximality. External and biostromal microfacies have mean MS values

around 2x10-8 m/kg, while the lagoonal facies shows mean values around 6.7x10 -8

m/kg. Furthermore a main remagnetization event was recognized in the Devonian of

the Ardennes (Zegers et al., 2003), interpreted to be tied to burial whereby the smectite

to illite conversion, providing the source of the iron for the remagnetized magnetic

minerals. A full understanding of what is driving the magnetic susceptibility signal iscritical to a better understanding of its origin. To further investigate the link between

magnetic parameters, facies and diagenesis an extended rock-magnetic characterization

was performed on a selection of samples; providing an extended magnetic property data

set with hysteresis measurements and IRM (isothermal remanent magnetization)

acquisition curves, both at room temperature, in an attempt to explain the origin of the

magnetic susceptibility signal in these sediments.

Hysteresis curves allow to differenciate the paramagnetic, diamagnetic and

ferromagnetic contributions and it appears that for a majority of the samples the amount

of paramagnetic minerals (probably clays) is either low or magnetically insignificant (in

62% of samples), the signal being only dominated by ferromagnetic and diamagneticminerals (carbonates).

The IRM acquisition curves were analyzed by cumulative log-caussian (CLG) functions,

using the excel workbook developed by Kruiver et al. (2001). Most IRM acquisition

curves are rather similar, dominated by magnetite (between 80 and 100%) with a

relatively limited amount of non saturated minerals (probably hematite, which is the

dominant ferromagnetic component in 3 samples). Evidently, hysteresis curves also

show the dominant influence of magnetite for the ferromagnetic contribution. In many

cases the high-field contribution of the non-staurating part of the IRM acquisition

curves appears to be included in the paramagnetic slope correction procedure making its

detection difficult in hysteresis loops.


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References

da Silva, A.-C. and Boulvain, F., 2006. Upper Devonian Carbonate Platform Correlations and Sea Level

Variations Recorded in Magnetic Susceptibility.Palaeo3, 240, 373388.

Kruiver, P.P., Dekkers, M.J. and Heslop, D., 2001. Quantification of Magnetic Coercivity Components by

the Analysis of Acquisition Curves of Isothermal Remanent Magnetisation.EPSL, 189, 269276.

Zegers, T.E., Dekkers, M.J. and Baily, S. (2003) Late Carboniferous to Permian remagnetization of

Devonian limestones in the Ardennes: Role of temperature, fluids, and deformation. JGR, 108, 5/1 -

5/19.5/1 - 5/19


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Abstract -2

Complex pathways of iron uptake in stromatoporoid skeletons:

variability mapped by magnetic susceptibility

J. Hladil1*, L. Koptikova1, P. Schnabl1, S. Slechta1, A. Galle1, L. Strnad2, V. Drabkova3

1 Institute of Geology AS CR, v.v.i., Rozvojova 269, 165 00 Prague 6, Czech Republic

([email protected])

2 Laboratories of Geological Institutes, Charles University, Albertov 6, 128 43 Prague 2, Czech

Republic

3 c.i., Refugio de San Nicolas de Bujaruelo, 22376 Huesca-Torla, Pyrenees, Spain

Motto:My experience related toPoritesstudied on Barbados in 1974 taught me that

the growth band series on different sides of a large coral head may contain entirely

different sorts of records; not surprisingly, the data are hardly comparable.... (Colin W.

Stearn, renowned guru of stromatoporoid studies pers. comm.., c., May 2007).

Our preceding and continued studies made on early Middle GivetianActinostromafrom

Byci skala in Moravian Karst backreef limestone complex came with the LA-ICP-MS

(and acid digested sample based ICP-MS) evidence that banding-related distribution of

iron in LDLBs and HDDBs (Lisy et al., herein) is far more complicated than simplified

interpretation models usually permit. In these stromatoporoids, three types (A, B and C)

of seasonal banding were recorded, each prevailing in short periods of decadal scale.

According to complete trace element analyses, the system A was introduced as hot,humid, of monsoon type and occurrence of two HDDBs per a year. The structure of the

system B was extremely regular and distinctly unimodal. The short HDDBs showed hot

triggering (low Sr/Ca) . The system C corresponded to periods with wild and strong

atmospheric-ocean circulation patterns. The HDDBs of A and C systems are connected

with high-Sr and high-Ba compositions. According to Fe/Ca ratios, the Fe

concentrations in system A behave quite unpredictably, i.e., with low difference betweenLDLBs and HDDBs, with alternating preferences to one or the other, and in addition, with

occurrence of shorter but also longer than annual rhythms. The system B, with the

lowest contents of iron, is characterized by slight correlation of increased Fe

concentrations with hot-type strangulations. In detail, this relationship also displayssome disturbances and failures. In the system C, the remarkably increased and strongly

fluctuating contents of iron are almost lacking any rhythmic control most of the

patterns on intra- and inter-annual scales are unique. One of the most interesting

findings was that increased Ba/Fe (~Ba/Ca) is almost perfectly marking the HDDBs of

the system C (HDDBs triggered by increased eolian-dust/ river-mud flux, the delivery of

dirt to high-purity reef environments). For the systems A and B, this relationship is not

working, and there was recorded several years with anomalous Ba depletions in HDDBs

(removal associated with biological productivity?). These results have cast much doubt

on the still prevailing concepts of regularity in iron uptake where one of possible

mechanism of control can be dominant for some longer time.

These Moravian studies were recently extended also to early Late Frasnian


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stromatoporids from Mokra Quarry West (Mokra facies assemblage, Moravian Karst

area). Close above the base of the upper rhenanaZ. equivalent, unusually fast growing

and regularly shaped Stromatopora provided a good opportunity to sample, cut and

assess the growth bands. The reasons were two. First, to extend the techniques of

mapping of iron concentrations in skeletons by magnetic susceptibility, and second, to

confirm or refute the suspect differences between the growth bands on the front andback of such heads or boulders; compare the motto. The stromatoporoid heads were

sliced parallel to front-back direction; prisms were cut from central slices, oriented 45 o

upwards, reaching the terminal surface A prism and log = back of colony, B = front. For

preparation of optical log scale we refer to Lisy et al., herein. The records from the last

17 years of one colony (= 2 x 34 sampled zones) exemplify the results of this study.

Although the LDLBs and HDDBs maxima and minima can quite easily be identified and

interconnected (based on smoothing, verified condition that no one is missing), the

major differences in the structure of all coeval intra- and inter-annual patterns are

critical. The evidence of this was provided by means of dynamic time warping

techniques, where DTW failed to find A-B alignments for all bands together; this relatesalso to smoothed and/or low-pass filtered data (e.g. Hamming). Even if partial, e.g. 4-6

yr segments are aligned, step by step, the plausible alignments relate to great loss of

information on input and output; must be rejected. The comparison of averages for

whole LDLBs and HDDBs optical values (D) and whole LDLBs and HDDBs magnetic

susceptibility (MS) shows the following: Certain regularities of D to MS behaviour

exist in 4-6 year segments, but are different for A and B sides. Overall D and MS trends

(and also match or mismatch on coupled positions of D and MS peaks and valleys)

differ in ~80%. By means of correlation of peak and valleyaverage values, the

correlation coefficient are: DADB 0.68, MSAMSB -0.22; DAMSA 0.00, DBMSB

-0.09. MS values [10-9 m3/kg]: A -1.412.4 (1.4); B -0.821.17 (0.09). Theinterpretation outlines are based mainly on two concurrent mechanisms: solutescrystal

lattice, chemical/biochemical, and in-built flux of nano/micro-particles. At least five

other secondary micro-environmental factors are suspect (e.g., light; seawater acidity,

EhpH, redox; direct staining from the surface; pore-cement system in lower

abandoned zones, organomineralization, Corg, EhpH, redox again; late diagenetic

re-concentrations in minute accessory mineral phases....). *Projects: IAAX00130702

and IGCP 580.


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Abstract -3

Petromagnetic indications of environmental changes in the Devonian

Carboniferous boundary section in Poland (Pomerania region)

K. Sobien, H. Matyja , M. Stempien-Salek2, K. Malkowski

3

1 Department of Deep Structures Geological Mapping, Polish Geological Institute-National

Research Institute, 4Rakowiecka Street, 00-975 Warsaw, Poland, e-mail:

[email protected]

2 Institute of Geological Sciences, Polish Academy of Sciences, 51/55 Twarda Street, 00-118

Warsaw, Poland

3 Institute of Palaeobiology, Polish Academy of Sciences, 51/55 Twarda Street, 00-118 Warsaw,

Poland

High resolution biostratigraphic, rock magnetic and carbon, oxygen isotope studies

were performed on the offshore shale and carbonate condensed section from the

uppermost Famennian to the lowermost Tournaisian in the Pomerania region (Chmielno

1 borehole, NW Poland). Some conodont and enomozoid ostracode species as well as

three miospore zones of Streel were recognized, i.e. Retispora

lepidophyta-Indotriradites explanatus (LE), R. lepidophyta-Verrucosisporites nitidus

(LN), Vallatisporites vallatus-Tetusotriletes incohatus (VI). This

transgressive-regressive succession consists of dark clayey deposits and marly

calcarenites, which are equivalent to the multiphase Hangenberg Event.

Measurements of the magnetic susceptibility (MS, Agico KLY-2 Kappabridge) as well

as selected rock magnetic properties such as anhysteretic remanent magnetization

(ARM), isothermal remanent magnetization (IRM) and S parameter have been

performed in the Palaeomagnetic Laboratory of the Polish Geological Institute NRI.

93 samples in a scale of 20 meters section provided detailed picture of environmental

changes. Famennian-Tournaisian boundary interval is characterized by the lowest MS

values (of about 23 *10-6 SI), which partly correspond to some lithological changes and

a presence of regressive carbonates. Rapid MS drop in marly limestones in the upper

part of the Ra local miospore zone (~middle expansa) corresponds to a positive delta 13

C (carbon sedimentary organic matter) excursion and an increase of the delta 18 O value(oxygen isotopic composition of micrite). Significant MS increase in a marly shale

interval on the duplicata/ sandbergiboundary zone is coincident with a decrease of the

delta 13 C and subsequent increase of the delta 18 O.

MS rise and fall event of smaller amplitude is recognized in several miospore zones: VI

and Ma0 (~sulcata/duplicata conodont zones), LE (~lower/middlepraesulcata) as well

as in the lowermost LN (~upperpraesulcata).

The remanent magnetization measurements (ARM, IRM) show quite negative

correlation with the magnetic susceptibility signal, which is strongly influenced by

carbonates. Clear increase of the ARM values points to a considerable higher

concentration of the ferromagnetic minerals, which reflects regressive environment and

terrigenous material supply in the Chmielno 1 D/C boundary section. Variations in the


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ferromagnetic mineral concentrations present in the rocks studied reveal distinct cyclic

pattern, that possibly records fluctuating climate changes.


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Abstract -4

Upper Permian Sedimentary Environments of Indian Gondwana

Basins: Evidences from Magnetic Anisotropy

V. Prasannakumar, P. Pratheesh, R. Reghunath

Department of Geology, University of Kerala, Trivandrum, India 695581,

(mail:[email protected])

Permo-Carboniferous Period, characterized by glaciations, floral abundance, large scale

sedimentation, aridity and massive outpouring of lava, is traceable in Gondwana

fragments that were once part of a supercontinent known as Gondwanaland, and are

presently located in different continents. Permo-Triassic sedimentation and associated

rifting account for the development of a 3- to 5-km thick sequence of heterogeneouscontinental sediments in the Gondwana group of basins in India. Gondwana rocks occur

mainly in trough like depressions along the fault/shear zones, which are parallel to the

ancient structural lineaments, of Peninsular India. Since the basins indicate a

predominantly lacustrine environment with local marine transgressions and the

individual basins show wide variation in depositional pattern, detailed study of these

formations are expected to unravel spatio-temporal variation of the diversified

environment that existed in different Gondwana fragments during the

Palaeozoic-Mesozoic transition.

Raniganj basin, located in the Damodar valley area, Peninsular India, with an aerialcoverage of about 3000km2in a semi-elliptical or elongated shape is a typical example

for the Lower Gondwana sedimentation. The formation consists of fine to medium

grained sandstone, carbonaceous shales, traps and coal seams. Systematic analysis of

core samples, from an approximate depth of 480m, using Anisotropy of Magnetic

Susceptibility (AMS) provided indicative signatures of the sedimentary environment

that prevailed during the Upper Permian Period. Samples of sandstone as well as shale

show an oblate fabric (TAvg = 0.591) with considerable degree of anisotropy (PjAvg..=

1.053). But, the mean susceptibility of sandstone is comparatively low (Km Avg. = 121

E-06 SI), while the shale shows relatively high mean susceptibility (Km Avg. = 293 E-06

SI). Magnetic lineations are sub-horizontal and depict an E-W trend which is inagreement with the trend of the basin as well as the paleocurrent direction deduced from

sedimentological studies. The anisotropy also suggests a lacustrine condition for the

origin of these sediments in terms of strong magnetic foliation (>1) and prolate fabric

condition. Detailed analysis of magnetic fabrics is attempted to derive characteristic

magnetic parameters that can be effectively used to correlate the sequence stratigraphy

in various Gondwana fragments occupying different continents, which in turn can help

in the reconstruction of Gondwanaland. It is also proposed to utilize the magnetic

parameters for the systematic analysis as well as inter- and intra-continental comparison

and correlation of sedimentary environments in Mesozoic and Cenozoic.


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Abstract -5

The effect of different acid dissolution methods on magnetic properties

of insoluble residues of limestones

L. Koptikova*1, 2

, P. Schnabl1, 2

, R. Skala1, F. Vacek

3, S. Slechta

1, 2, V. Bohmov

1& M.

Stastny1

1 Institute of Geology, ASCR, v.v.i., Rozvojova 269, 16500 Prague 6, Czech Republic

([email protected])

2 Charles University in Prague, Faculty of Science, Albertov 6, 12843 Prague 2, Czech

Republic

3 School of Geography, Earth & Environmental Sciences, University of Birmingham, Aston

Webb A Block, Edgbaston, Birmingham B15 2TT, United Kingdom

The kind of acid used for solution of limestone samples has a not negligibleconsequence for the composition and magnetic properties of the residues. The same

applies to acid concentration and other conditions. The studies on mineralogical and

magneto-mineralogical properties of these residues relate to identification of the carriers

of whole-rock magnetism, but there is still a lot of work to do if the comparison

between the parameters of limestones and residues is to be really providing the better

understanding of complexity in MS carriers of rock magnetism.

Several magnetic properties of insoluble residues of the Lower Devonian limestone

(Lochkovian beds of the Pozar 3 section near Praha-Reporyje, Prague Synform) were

assessed after the dissolution in three different acids (acetic, formic and hydrochloric) to

test the influence these acid solution methods on the resulting composition of theseresidues. For characterization of light and heavy fractions of residues, a large array of

methods and techniques was used: e.g., measurements of magnetic susceptibility (MS),

temperature, field and frequency dependance of MS, isothermal remanent magnetization

(IRM), saturated isothermal remanent magnetization (SIRM) or anhysteretic remanent

magnetization (ARM), together with X-ray diffraction (XRD) identification of clay

minerals, or scanning electron microprobe (SEM WDA) analyses of non-carbonate

particles, grains or low carbonated aggregates. The results obtained on residues were

compared with those that were obtained using the whole-rock samples (and also solutes

contained in the fluid phase), to ascertain the control parameters for possible dissolution

of some important magnetic carriers such as Fe-oxides and oxyhydroxides in theseacids.

This study continues the previous work on insoluble residues from the Lochkovian to

Emsian Por 3 section (Koptikova et al. 2010 Geologica Belgica, 13, 4, 407-430), as

well as the first results made on the two sets of insoluble residues, based on solution in

acetic and hydrochloric acid, limestones from the Silurian-Devonian boundary beds

across the Prague Synform (Vacek et al. 2010 - Geologica Carpathica, 61, 4, 257-272).

The continued studies reveal that the hydrochloric acid solution is causing almost

complete dissolution of magnetite and hematite grains. But at the same the SIRM curve

can detect small amounts of these minerals which can be explained by their later

neoformation. The details of these and other parallel comparisons are indicative of close

relationships between the chemistry, lattice defects, inclusions, aggregation or


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characteristics of dielectric surfaces in sutures or interstitial space and degree of

instability. XRD analyses showed that all diffractograms are very similar in general but

slight differences can be identified in spite of the fact that the amounts of identified

mineral phases could be over- or underestimated due to the fact that the detection limit

of this method appears to be very rough (1 to 5% related to identifiable phase), being

also dependent on the coexisting phases and their composition, phase crystallinity or itspreferential arrangement. These problems were eliminated using the SEM EDA and

WDA analyses of individual grains and polished aggregates from each density fraction.

Quartz, feldspars (mostly microcline), clay minerals (illite, kaolinite), micas

(muscovite), pyrite and gypsum were identified as the most common mineral phases.

Phases such as marcasite, grains of pyroxene and amphibole elemental compositions or

rutile were found irregularly, in accessory and fluctuating amounts, but even these small

amounts must be considered. And finally, there is a specific area of problems which

relate to reconcentration of the lattice iron in many paramagnetic or generally low

magnetic phases (e.g. micas, clay minerals, feldspars, phosphates, glauconite and so

forth) where this iron is assembled into complex, more or less crystalline mineralaggregates of nano- to micrometric sizes. The insoluble residues from the acetic acid

show significantly higher variability in the mineral composition (the occurrence of

different clay minerals, variability in the amount of mica) as well as more fluctuating

magnetic properties than the other residues obtained by dissolution in formic and

especially hydrochloric acid.

In all studied samples of these Lochkovian limestones, the non-carbonate impurity

contains a predominant quantity of mineral phases with paramagnetic behaviour. The

MS signal from paramagnetic iron species in the samples represents the major part of

MS stratigraphic variation with smaller than usual contribution by ferromagnetic

components. Projects: P210/10/2351 and IGCP 580.


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Abstract -6

Rock magnetism, sedimentology, gamma-ray logging, reefal and

peri-reefal fauna in the Mont dHaurs and Fromelennes formations

(Late Givetian) at Cul dHouille section (Flohimont, France)

E. Petitclerc1, X. Devleeschouwer

1,4, B.L.M. Hubert

2, E. Pinte

2, S. Maillet

2, C. Crnier

2, A.

Bignon2, S. Spassov

3, A. Prat

4

1 Royal Belgian Institute of Natural Sciences, 13 Rue Jenner, B-1000 Brussels, Belgium.

([email protected]; [email protected])

2 Laboratoire Gosystmes, FRE 3298 CNRS, USTL, UFR des Sciences de la Terre - btiment

SN5, F- 59655 Villeneuve d'Ascq cedex, France.([email protected];

[email protected]; [email protected]: [email protected];

[email protected])3 Royal Meteorological Institute of Belgium, Centre de Physique du Globe, Section du

Magntisme Environnemental, B-5670 Dourbes, Belgium. ([email protected])

4 Department of Earth and Environmental Sciences, Sedimentology and Basin Analysis,

Universit Libre de Bruxelles CP 160/02, 50 av F.D. Roosevelt, B-1050 Brussels, Belgium.

([email protected])

The Cul dHouille section is located near Flohimont (France) in the southern part of

the allochthonous Ardennes fold-and-thrust belt and partly exposes the Mont dHaurs

(MHR) and Fromelennes (FRO) formations. The boundary between MHR and FRO

formations corresponds to the transition from reefal limestones to argillaceouslimestones and siltstones. The successive Flohimont, Moulin-Boreux and Fort Hulobiet

Members of the FRO Fm. consist of discontinuous outcrops due to bad exposure

conditions implying unclear limits between these different members. On the field, 780

samples were collected along 236 meters. The peri- and reefal fauna (stromatoporoids,

tabulate corals, trilobites and ostracods) were studied to estimate biodiversity and

ecological trends. The sedimentological study and the low-field magnetic susceptibity

(XLF) were done for all the samples. Gamma-Ray spectrometry logging was obtained on

the field with a density of one measurement every 25 cm representing more than 700

measurements.

The MHR Fm. shows a high diversity of stromatoporoids and tabulate corals (lamellar,

branching and massive forms).The passage to the Flohimont Mbr. (FRO Fm.) is marked

by a decrease of the diversity (only some lamellar forms and branching like Alveolitids

and Thamnoporids for tabulates and Clathrocoilona for stromatoporoids). The Moulin

Boreux Mbr. registered a low diversity. Reefal fauna is mainly represented by small

branching organisms like Scoliopora and Amphipora. They are considered as

opportunist fauna and are present in unfavourable environments. The trilobite

distribution shows a low diversity. It is mainly represented by the Dechenellagenus in

the middle part of the Flohimont Mbr.

The sedimentological analysis recorded 13 microfacies (using the Givetian standardsequence of Prat & Mamet, 1989) ranging from open-marine to restricted supratidal

environments. The evolution of the microfacies curve allows the recognition of


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numerous regressive intervals in the MHR Fm., of two important transgressive

intervals in the Flohimont and Fort Hulobiet Mbr. and of several small-scale cycles in

the Moulin Boreux Mbr. from deepest to shallowest environments. The general

environment is the one of bioclasic (mainly algae) shoals submitted to an high energy

index. In this context the reefal barrier is limited and systematically destroyed in this

shallow water domain.

XLF evolutions along the lithological column are characteristic for each Fromelennes

member and for the Mont dHaurs Fm. Microfacies and XLF curves are slightly

correlated except for the base of the Flohimont Mbr. where MF and XLF curves are

anti-correlated. Hysteresis parameters calculated from hysteresis curves indicate (1) that

ferromagnetic minerals (essentially the low coercivity phase) mostly controlled the XLF

curve even if the diamagnetic and paramagnetic minerals are participating to the signal

(2) that Flohimont and Fort Hulobiet Mbr. record a higher contribution of ferromagnetic

minerals (3) that a weak contribution of a high coercivity mineral phase (e.g. hematite)

ranging between 1 and 12% is observed throughout the section (4) that magnetite

nanoparticles (close to the SP-SD domains) are significantly more abundant in the

Moulin Boreux and Fort Hulobiet Mbr.


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Abstract -7

Rock magnetism and sedimentology at the Hanonet/Trois-Fontaines

transition (base of the Givetian, Belgium) in the Fondry des Chiens

and Mont dHaurs sections

X. Devleeschouwer1,3

, E. Petitclerc1, S. Spassov

2, A. Prat

3

1 Royal Belgian Institute of Natural Sciences, 13 Rue Jenner, B-1000 Brussels, Belgium.

([email protected]; [email protected])

2 Royal Meteorological Institute of Belgium, Centre de Physique du Globe, Section du

Magntisme Environnemental, B-5670 Dourbes, Belgium. ([email protected])

3 Department of Earth and Environmental Sciences, Sedimentology and Basin Analysis,

Universit Libre de Bruxelles CP 160/02, 50 av F.D. Roosevelt, B-1050 Brussels, Belgium.

([email protected])

The Mont dHaurs (MHR) section (Givet, France) is exposed on the eastern side of the

Meuse river and the Fondry des Chiens (FC) section (Nismes, Belgium) is located

about 22 km SW of Givet. Both outcrops belong to the allochtonous Ardennes

fold-and-thrust belt. The base of the MHR lithological column correspond to the end of

the Hanonet Fm. represented by 11 meters of argillaceous limestones containing

crinoids, solitary rugose corals, stromatoporoids and gastropods. The base of the

Trois-Fontaines Fm. consists of 5 meters of massive limestones with stromatoporoids

and corals corresponding to a large biostromal unit. Ten meters of well-stratified

argillaceous grey limestones are present above the biostrome.

The FC section exposes vertical layers slightly reversed towards the south in a karstic

depression. The upper part of the Hanonet Fm. consists of crinoidal limestones followed

by a 64 m thick biohermal lens composed of stromatoporoid-coral framestones

belonging to the Trois-Fontaines (TRF) Fm. Above the bioherm, 28 meters of thin

bedded algal and sponge limestones are observed. 52 and 113 samples were collected

respectively for MHR and FC sections for sedimentology and magnetic susceptibility

analyses.

During the Lower Givetian, a large carbonate platform developed throughout northern

Europe overlies a mixed silicoclastic-carbonate ramp, which characterises the HanonetFm. The microfacies curve of FC is composed of a succession of 10 carbonate

microfacies. The deepest microfacies (MF1) is an open marine environment at the upper

limit of the storm waves and the dysphotic-euphotic boundary. The shallowest

sediments were partly emerged (lagoonal sediments, MF10). The exposed reefal lens

(rudstones and framestones, MF6-7) and the flanks (grainstones, floastones and

coverstones, MF3-4-5) of two other lenses are preserved. Altough the standard sequence

is not complete as it was in FC (due to the absence of a biohemral lens) the

sedimentological evolution is the same with a pronounced regressive eustatic evolution

from open marine settings to near emerged lagoonal environments with abundant

loferites. The reefal lens (stromatoporoid framestone) is here replaced by a biostromewith stromatoporoid and coralgal floatstones and rudstones. The overlying lagoon is

similar in both sections with the predominance of calcispheres and kamaenids. MF


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curves record the evolution from carbonate middle ramp to inner ramp conditions and

then the change towards an inner restricted carbonate platform in the first lagoonal

limestones of the Trois-Fontaines Fm.

The FC section is subdivided into 5 XLFmagnetic sequences. XLFand MF data seems to

be only well correlated in magnetic sequence 1, 2 and 5. Ferromagnetic susceptibility

(XFerro) and XLF are strongly correlated (R = 0.99) indicating that the magnetic

susceptibility signal is mostly controlled by ferromagnetic minerals (e.g. magnetite).

Increasing values of XFerro and isothermal remanence magnetization at 500 mT

(IRM500mT) are observed in the lagoonal sediments of the Trois-Fontaines Fm. High

normalized magnetic viscosity coefficient (Sd) values (0.053) are present in the

lagoonal part of the Trois-Fontaines Fm. The contributions of a high coercivity phase to

the IRM500mT ranges between 7.3 % and 25% throughout the section and are

anti-correlated with Sd values. Consequently the magnetic nanoparticles present in the

samples are probably related to a low coercivity phase (i.e. magnetite).

The XLF values of the MHR section are globally lower than the FC section andfluctuates along 4 XLF magnetic sequences. A clear correlation between XLF and MF

curves is observed. XFerroand XLFare also strongly correlated (R = 0.98) indicating that

XLF is also mostly controlled by ferromagnetic minerals (e.g. magnetite). XFerro and

IRM500mT are characterized by stronger values in the lagoonal facies of the

Trois-Fontaines Fm. The contributions of high coercivity minerals to the IRM500mTand

Sd values are anti-correlated indicating that nanoparticles are probably related to a low

coercivity phase (i.e. magnetite).

Rock magnetism results confirm thus: (1) the presence of a low (magnetite?) and high

coercivity (hematite/goethite?) phases in the limestones at the base of the Givetian; (2)

that paramagnetic contribution is largely dominant in most of the samples except those

in the lagoonal sediment where a ferromagnetics.l.contribution is observed; (3) that Sd

values are higher for the Trois-Fontaines Fm. than for the Hanonet Fm. indicating the

presence of more ultra-fine grained magnetite nanoparticles in the Trois-Fontaines Fm.;

(4) that these nanomagnetites have a diagenetic origin; (5) the presence of a mixture of

SP-SD magnetite grains.


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Abstract -8

Recognition of Milankovitch cyclicity in Magnetic Susceptibility Data

with Wavelet Transform

J.F. Yu, W.Z. Fu, X.J. Lang

Shandong University of Science and Technology ([email protected])

Magnetic susceptibility (MS), also called the magnetic susceptibility intensity, refers to

magnetizing difficulty degree, and can indicate the subtle changes in rock types of

stratum. MS which depends on the preservation of iron-bearing minerals, has been

proved favorable as a paleoclimatic indicator (Curry et al., 1995; Robinson, 1993), and

thus for correlation purposes as a paleoclimate proxy (Shack-leton, 1999).Milankovitch

theory is proposed aiming at the global climate change, but it can be confirmed by the

sedimentary record periodicity, because the periodic climatic change will be reflected bythe sedimentary texture, the structure and the thickness of the sedimentary formation.

As a paleoclimatic indicator, MS should have relation with orbital forced cycles.

Identification of the cycles in MS of the stratum is helpful for geological studies. The

susceptibility data are non-stationary and conventional tools for analysis such as

autocorrelation, spectral analysis and semivariogram techniques have limited value

(Duncan Cowan, et al., 2003). Wavelet analysis can provide definitive information on

the scaling properties of magnetic susceptibility needed to determine 'formation

response' or facies variation. In Duncans research, continuous wavelet transform(CWT)

using a Morlet wavelet helped to quantify the periodicity of the layering, and discrete

wavelet transform (DWT) using a Haar wavelet provided an effective means of'blocking' the log, but cyclical information was not given. Based on their study, through

the establishment of ideal curve model and masses of experimental studies, we can

calculate the cyclical size only using One-Dimensional Continuous Wavelet Transform

of Morlet wavelet. The position that response the superiority period can be identified,

and the cyclical number that contained in some stratigraphic interval can be calculated.

The vibration amplitude of wavelet coefficient curve responds the significant degree of

cycles that contained in different layers.

In the case study, The MS data is taking from the curve of Early Triassic profile of

Pingding Mountain in Chaohu Anhui(from Guo Gang, Tong Jinnan et al.), in which two

superiority cycles that respectively are 0.9231m and 5.1077m cycles are distinguished.

Ratio of the two cyclical approximately is 1:5.5, which is basically same with that of the

precession and the short eccentricity cycle. It is regarded as the response to the

Milankovitch cyclicity. The criterions that respond two superiority cycles are

respectively 15 and 83. During the stratigraphic interval 0-30m, the 0.9231m cycle

responds well and there are about 32 cycles. However, the 5.1077m cycle responds well

during the stratigraphic interval 20-35m, and there are 3 to 4 cycles. Thus

One-Dimensional Continuous Wavelet Transform is feasible for distinguishing the

Milankovitch cyclicity in MS data. Guo gang, Tong Jinnan(2007) have determined the

superiority cycle by Fast Fourier Transform Algorithm (FFT) and Welch Law, and theresult of them is 0.76m and 3.41m. Which result is more accurate should be researched

in the future.


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Abstract -9

Local remagnetization of sedimentary and volcanosedimentary rocks

from Barrandian area (Prague Synform, Bohemian Massif)

P. Schnabl*1,2

, S. Slechta1,2

, L. Koptikova1,2

, P. Lisy1, P. Cejchan

1, F. Vacek

3, Z. Tasaryova

4,

J. Hladil1, P. Pruner

1

1 Institute of Geology ASCR, v.v.i., Rozvojova 269, 16500 Prague 6, Czech Republic

([email protected])

2 Institute of Geology, Faculty of Science, Albertov 6, 12843 Prague 2, Czech Republic

3 Earth Sciences, University of Birmingham, Aston Webb A Block, Edgbaston, Birmingham

B15 2TT, United Kingdom

4 Czech Geological Survey, Klarov 3, 118 21 Prague 1, Czech Republic

Remagnetization causes problems during interpretation of magnetic susceptibility (MS)

signal. Some of the lower Palaeozoic rocks are slightly remagnetized while rock bodies

around fault and fracture zones are strongly remagnetized. The major newly formed

minerals that increase the rock MS are hematite, superparamagnetic (SP) magnetite and

goethite. Although the effects of superparamagnetic goethite on the total rock MS signal

have rarely been studied in limestones and carbonated sedimentary rocks in detail, the

present study indicates that it is not an insignificant component contributing to the

analyzed MS signal. According to evidence from thin sections and insoluble residues,

goethite represents a quite ubiquitous component in these rocks. In Barrandian

limestones and adjacent strata successions, the hematite enrichment of Variscan origin isquite regularly found at the bigger faults as well as accompanying or separate fracture

zones, where an apparent evidence of this kind of mineral change is the reddish colour

hue of rocks. Increased hematite contents were detected also by means of

magnetomineralogic methods. The remagnetization corresponding to this change in

rocks of Silurian and Devonian ages has a solid evidence base since being dated by the

late Carboniferous to early Permian palaeomagnetic directions. There is also a

possibility that some hematite enrichments of this type are older, formed as early as with

the major eo-Variscan deformation of these limestones during the late Devonian ages,

but the final remagnetization is in most of the cases late Carboniferous/ Permian.

Even minor enrichment by SP magnetite which has several orders higher MS than most

minerals can degrade the MS signal; SP magnetite can be easily proved by frequency

dependent MS. Some of the rocks are enriched during supergenic processes by goethite

because the Barrandian area is affected, on many places, by deeply penetrating

weathering of wild relief. The occurrence and amounts of goethite can be easily proved

by acquisition of isothermal remanent magnetization (IRM). The above mentioned

remagnetization episodes can also be proved by fold, conglomerate and dike tests.

The problems related to populations and neomorphism of magnetite and goethite have

already been studied, and the preliminary results were published (Vacek et al. 2010,

Geol. Carpath.). Here, the authors proved on several localities of SilurianDevonianboundary successions that there are also just opposite situations. There are also large


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rock bodies and spots in the Barrandian area (exactly in the Prague Synform) where the

remagnetization has a negligible importance in sum of these diagenetic and

remagnetization changes. On the other hand remagnetization play very important role in

many cases. It is particularly relevant to the Reporyje Limestone of early Devonian (late

Pragian) age. In Reporyje limestone, great amount of hematite was embedded in

synsedimentary to early diagenetic conditions, being related to precipitates inmicroborings and internal pores of altered bioclasts in general. In spite of this fact, the

major part of this hematite was gradually recrystallized, and in the present state, the

remagnetization overprint with CarboniferousPermian palaeomagnetic directions

strongly prevails.

The contribution for discussion is how to recognise MS depletion, which was according

to our knowledge never studied. One of the newly introduced methods consists in the

measuring of basaltic dykes which intruded into the limestone layers. The basaltic dyke

that intruded into the limestone layers on the site Jelinkuv Mlyn (quarry) shows a strong

MS depletion on the volcanic rock, so that there is also evident potential that also MS of

surrounding limestones was changed. Our preliminary data show, e.g., that average MS

depletion on one set of Silurian basaltic dykes is between 95 and 98 percent, while a

second set is absolutely untouched with the late diagenetic episodes or by weathering.

The palaeomagnetic signal of the emplacement time is usually recorded in the contact

aureole. However, also the diagenetic history and preservation of older magnetic

mineral carriers in these most promising contact objects is diversified so that they do

not need to be an absolutely reliable source of magnetic information in all imaginable

cases.

In summary, the remagnetization studies are necessary for proper interpretations of MS

record, and the almost any kind of MS enrichment is, at least theoretically, detectable. /Projects: P210/10/2351, IAAX00130702 and IGCP 580.


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Abstract -10

Differential geochemical response during the lower and upper

Kellwasser events, western Canada: Implications for global change

M.T. Whalen1, J.H. Payne2, J.E Day3, M.G. Sliwinski1

1 Dept. of Geology and Geophysics, University of Alaska Fairbanks, Fairbanks, Alaska

([email protected])

2 Shell Exploration and Production Co., 150-A North Dairy Ashford, Houston, Texas

3 Department of Geography-Geology, Illinois State University, Normal, Illinois

The Late Devonian Lower and Upper Kellwasser mass extinction events (LKE & UKE)

are linked to episodes of global change and episodic low oxygen conditions. We report

the results of facies, major and trace element analyses, organic carbon and nitrogenstable isotopic analyses and the magnetic susceptibility (MS) of rocks from western

Canada that provide insight into paleoenvironmental change during these events. These

data are evaluated within a sequence stratigraphic framework, which indicates that the

LKE and UKE intervals were both deposited during lowstand and early marine

transgression of Late Devonian sea-level events IId-2 and IIe. They, however, display

markedly different geochemical signatures. Ni, Cu, and Zn, are micronutrients used

by marine primary producers and are at background levels in our study sections except

within the LKE and UKE. Si, Ti, and Zr are useful indicators of terrigenous influx or

dilution and display increasing values during the events. Likewise, the MS signature

displays a significant increase during the Frasnian leading up to the LKE and both theLKE and UKE display positive MS excursions in proximal basinal settings. Mo, U,

and Corg:P are useful redox proxies and all are enriched within the event intervals. The

events are both associated with positive 13Corg excursions (~3-4). The 15Norg

signature covaried with 13Corgand generally increased during the events.

The above proxies display several abrupt fluctuations during the LKE while the UKE

records a single long-term perturbation in most proxies. Generally the LKE records

increasing proxy levels upsection with Ni, Cu, Zn, and Ba indicating heightened

productivity. Elevated levels of Si, Ti, and Zr signify an increase in terrigenous influx

that is mirrored by positive MS excursions. High concentrations of U, Mo, and Corg:P

ratios imply decreasing bottom water oxygen levels. High Corg and positive 13Corg

excursions implying increased carbon burial. 15Norgvaries from lowstand (-2-0) to

transgression (>6) and such positive excursions in 15Norg suggest a change from

nitrogen fixation to denitrification. These patterns are similar to those observed during

recent and Carboniferous interglacial to glacial cycles. A series of interrelated

paleoclimatic, tectonic and sea level events appear to have driven the biotic change

during the LKE and UKE. Late Devonian orogenic uplift in northern Laurasia fostered

increased continental weathering, as did the evolution and expansion of rooted

terrestrial plants. The increased weathering influenced a drawdown of atmospheric CO2

resulting in climatic cooling. We hypothesize that the combination of increased

continental weathering during cooling-related sea-level drawdown and higher wind

stress, due to a greater pole-to-equator temperature gradient, also resulted in an increase


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in eolian dust transport. Increased dust flux and weathering products delivered by

fluvial systems to the oceans during lowstand and early transgression ultimately resulted

in higher productivity fueled by terrigenous nutrient delivery. High productivity

resulted in organic carbon burial and related episodic suboxic conditions. The pattern of

rapid change recorded during the LKE may mark the beginning-of-the-end of the Late

Devonian greenhouse world and the initiation of small-scale continental glaciers. TheUKE appears to represent a long term cooling event leading up to the Carboniferous

icehouse world.


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Abstract -11

Non-magnetic proxies of pedogenesis related to Chinese and

Siberian/Alaskan model of magnetic alteration of loess; examples

from Czech Republic and southern Siberia.

O. Bbek1,2

, J. Chlachula3, T.M. Grygar

4

1 Department of Geology, Palacky University of Olomouc, Olomouc, Czech Republic

([email protected])

2 Department of Geological Sciences, Masaryk University, Kotlsk 2, 61137 Brno, Czech

Republic ([email protected])

3 Laboratory for Palaeoecology, Institute of System Studies, T. Bata University of Zlin, Zlin,

Czech Republic

4 Institute of Inorganic Chemistry, Academy of Science of Czech Republic, Rez, CzechRepublic

We searched for non-magnetic proxies of the intensity of pedogenesis in loess/paleosol

sections from two different climate settings, Doln Vstonice, Central Europe, and

Krasnogorskoye, southern Siberia. The work was performed to overcome the problem

of two opposite scenarios of magnetic susceptibility (MS) patterns in these two profiles,

the "Chinese" model with magnetically enhanced paleosols and the Siberian/Alaskan

model with magnetically depleted paleosols. Age constraints of the Krasnogorskoye

section were inferred from independent correlation with the well-dated Doln Vstonice

section, based on MS and sediment colour (CIE L*), and with the MS log from the LakeBaikal. Pedologic description of the loess/paleosol sections and their correlation

potential was considerably improved by using Vis spectral proxies (CIEL*, reflectance

in the red band) while their weathering intensity can be effectively characterised by

diffuse reflectance spectroscopy (DRS) and geochemical (cation exchange capacity

/CEC/ and Rb/Ca ratio) proxies. While the MS is strongly dependent on the type of soil,

(chernozems vs. brown soils) the geochemical proxies, in particular CEC, proved to be

relatively independent on the soil type. These parameters are less affected by

region-specific conditions than the MS signal. Even the non-magnetic proxies indicate

relatively dissimilar climatic trends for the two sites during the last glacial-interglacial

cycle. A long-distance correlation, based solely on the MS signal, can be adversely

affected by switching between the Chinese and the Siberian/Alaskan magnetic modes,

which was observed at the Krasnogorskoye section. In general, no single universal

proxy of weathering or pedogenesis intensity exists, which would be applicable across

wide regions or across considerable climatic gradients. Palaeoclimatologic

interpretations across wide regions should always be based on a carefully designed,

multi-proxy approach.


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Abstract -12

Multiple isotopic constraints on the vast environmental changes during

the Frasnian-Famennian transition of Late Devonian

D.Z. Chen1, J.G. Wang

1, H.R. Qing

2, G. Racki

3, M.E. Tucker

4

1 Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing

100029, China (E-mail: [email protected])

2 Department of Geology, University of Regina, Regina SK, Canada S4S 0A2

3 Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warszawa,

Poland

4 Department of Earth Sciences, University of Durham, Durham DH1 3LE, UK

Sequence/cycle stratigraphic analysis revealed two third-order depositional sequencesacross the F-F boundary both in deep-water and shallow-water carbonate successions in

South China. An apparent sea-level fall, spanning four eccentricity-driven cycles (~400

kyr), and a subsequent rapid sea-level rise, spanning three precessional cycles (~50 kyr),

were recorded across the F-F boundary, and were temporally coincident with the two

phases of F-F stepwise biotic demise.

Multiple isotopic (13Ccarb-13Corg,

87Sr/86Sr, 34SCAS-34Spy) systematic studies were

carried out to constrain the vast environmental changes across F-F boundary in South

China and Poland. An overall parallel positive excursion of 13Ccarb-

13Corg pairs and87Sr/86Sr ratios, but an opposite trend in 34SCAS-

34Spy variations, are revealed; it

commenced at the onset of the apparent sea level fall through subsequent sea level rise.

During the interval of sea level fall, 13Ccarb-

13Corg pairs started an overall increase,

although with smaller-scale negative perturbations, in contrast, 87Sr/86Sr ratios

decreased or remained low values. The 34SCAS-34Spypairs, however, reached the maxima

at the beginning, which decreased episodically or remained persistent throughout the

interval. During subsequent rapid sea-level rise, concurrent positive excursions occurred

for both 13Ccarb-

13Corgpairs and87Sr/86Sr ratios, but with a delayed maximum in both

13Corg and

87Sr/86Sr ratios compared with the 13Ccarb variations. On the contrary,

parallel negative excursions of 34SCAS-34Spypairs occurred simultaneously and persisted

for about 300 kyr, although a short-term return took place in Poland.

The coincidence of positive excursions of 34SCAS-34Spy pairs (with increased

34S =34SCAS

34Spy) with short-term negative excursions of 13Corg or

13Ccarb values at the

onset of rapid sea level fall suggest a catastrophic oceanic overturn might have occurred

in the restricted stratified marine basins, which was probably induced by catastrophic

gravity flows or slope failure initially triggered by cataclysmic block tilting. The

coincidence of positive excursions of 13Ccarb-

13Corg pairs and87Sr/86Sr ratios with

negative excursions of 34SCAS-34Spy pairs during the subsequent rapid sea level rise

indicates a greatly enhanced primary productivity (or organic burial) and bacterial

sulfate reduction (BSR) in parallel with greatly increased continental nutrient fluxes and

oxidized sulfides (sulfate) supplies into oceans. The greatly enhanced organic burial andBSR, together with iron deficiency, could have produced excessive H2S being released


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into water columns even atmosphere, creating long-lasting extreme photic-zone euxinia.

The temporal coincidences of two main phases of step-down biotic crisis with the

oceanic overturn and subsequent long-lasting photic-zone euxinia, respectively, suggest

a causal link between them. Overturing of anoxic deep waters into the surface waters

could have caused severe suffocation of shallow-water benthons, leading to their

massive decline. Subsequent photic-zone euxinia would result in more fatal strike on the

benthic fauna that were persistently exposed to the toxic H2S gases, and cause a delayed

biotic recovery, probably along with the succeeding severe climatic cooling.


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Abstract -13

Frasnian/Famennian Boundary in Limestone Formations from Xom

NhaSection, Vietnam: using Paleontological and MSEC methods

T. P.L. Luu1, B.E. Brooks

2, H. P. Ta

3, S. Eberhard

4, H.T. Jonathan

5

1 Institute of Geophysics 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam. Phone: 84 48 363

238, Fax: 84 48 364696, E-mail: [email protected];

2 Department of Geology and Geophysics, Louisianna State University, Barton Rouge,

Louisianna 70803, USA, Email:[email protected]

3 Department of Geology, Natural science University, National University Thanh Xuan, Hanoi,

Vietnam;

4 Forschungs-Institut Senckenberg, Senckenberganlage 25, Frankfurt D-60325, Germany;

5 School of Earth, Society, and Environment, University of Illinois, 428 Natural HistoryBuilding, 1301 W. Green Street, Urbana, IL 61801, United States

We have been using magnetostratigraphy susceptibility (MS) for comparisons between

Frasnian-Famennian (F-F) boundary sequences, and here present the results from MS

measurement of 147 samples collected at 5 cm intervals over 7.3 m, in the entrance

room of Xom Nha Cave, Quang Binh, Middle Vietnam, and compare those results with

MS measurements for 92 samples collected at ~ 2 cm intervals through 1.82 m of the

Type Kellwasser locality within the Oker Reservoir area in the Harz Mountains,

Germany. Biostratigraphic control for high-resolution chronocorrelation is provided by

conodont zonation for both sections. MS zonation when compared with thebiostratigraphic zonation for these sites indicates that within the Xom Nha succession,

the first appearance of P. triangularis falls slightly higher (later) in Viet Nam than in

Germany. Given that these are very condensed sections, this difference is quite close

and not surprising. Spectral analysis using a Fourier Transform (FT) method resulted in

identification of Milankovitch cyclicity in the eccentricity (E2; ~100,000), obliquity

(~40,000) and precession (~20,000) bands, for both data sets (obliquity and precession

corrected for the Upper Devonian using the work of Berger et al., Science, 1992).

Graphic comparison between these two F/F boundary sections resulted in an excellent

correlation, with differences resulting from slight relative sediment accumulation rate

variations at each site. Graphic comparison of each MS data set against anobliquity-based MS climate standard zonation produced a striking similarity between

the MS zonation for each site and the climate zonation. Results from these comparisons

indicate that there is a change in the lowest Famennian in sediment accumulation rate at

both the Germany and Vietnamese sites toward slightly lower rates.


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Abstract -14

Wavelets: an alternative tool for MS-stratigraphic correlation

P. Cejchan*, L. Koptikova, J. Hladil

1


([email protected])

Motivation. MS-signal of rocks / dissolution residues may be useful for stratigraphic

correlation [1-2]. Despite the assumed common background magnetic-particle input

process, the MS-signals from different sites are distorted due to variable sedimentation

rate, input of magnetic particles rate, and variation in mineral/chemical composition of

MS-signal carriers. Thus, a problem arises, how to match (align, correlate) the distorted

signals. This problem is common in many areas of discrete signal processing, rangingfrom speech recognition to image registration. The major motivation and objective of

this work is to apply the wavelet correlation analysis in the MS-stratigraphic context.

Currently used methods. Observation of raw signals is still the prevailing method of

matching the MS curves. It is based on subjective recognition of patterns of peaks and

valleys in the signal, and matching corresponding points by hand. Cross-correlation is a

measure of similarity of two waveforms as a function of a time-lag applied to one of

them. It is useful in case when there is no difference in sedimentation rates, and other

conditions, and the signals are only displaced in time [3-4]. Dynamic time warping in

other hand can match two sequences which vary in time, speed, and amplitude.

Similarities can be detected, if there were differences in amplitude and even if therewere accelerations and decelerations during the course of the observatons. In general, it

is a method that allows a computer to find an optimal match between two given

sequences (e.g. time series) with certain restrictions, i.e. the sequences are "warped"

non-linearly to match each other. It was used for correlation of MS-sequences in [5].

Why wavelets? A continuous wavelet transform (CWT) is used to divide a

continuous-time function into wavelets. Unlike Fourier transform, the continuous

wavelet transform possesses the ability to construct a time-frequency representation of a

signal that offers very good time and frequency localization. Scaleogram is a visual

method of displaying a wavelet transform. It has 3 axes: first representing timing of an

event, second its scale, and third its intensity. The third axis is usually visualized by

varying colour or brightness. A scaleogram is an equivalent of a spectrogram for

wavelets. By decomposing a time series into timefrequency space, one is able to

determine both the dominant modes of variability and how those modes vary in time

[6].

Material, methods and results.Two MS logs from two sections across the Emsian -

Eifelian boundary (Devonian, Czechia) developed in limestones, were used for testing

of applicability of the wavelet scaleograms in stratigraphic correlation. Approximately

20-40 g samples of unweathered rock without calcite veins or dissolution seams were

taken in 5 centimetre-spaced rows in a vertical section across the boundary interval. Intotal, 6 to 8 metres were sampled at each section.


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For measurements, a Kappabridge KLY-2 device with a magnetic field intensity of 300

A.m-1, an operating frequency of 920 Hz and a sensitivity for specimen 4.10-8 SI was

used. Raw and normalized mass-specific MS [m3.kg-1] of whole-rock samples were

transformed by the CWT using the 'Mexicat Hat' (degree 2 Derivative of Gaussian)

mother wavelet.

We used the resulting wavelet scaleograms to find similar matching patterns in

frequency and amplitude domain. The results correspond well to those obtained by

classical method in the previous study [7].

[1] Crick, R.E., Ellwood, B.B., Feist R., Hladil, J., 1997. Magnetosusceptibility event and

cyclostratigraphy (MSEC) of the Eifelian-Givetian GSSP and associated boundary sequences in North

Africa and Europe. Episodes 20, 3, 167-175.

[2] Ellwood B.B., Crick R.E., El Hassani A., 1999. The magnetosusceptibility event and cyclostratigraphy

(MSEC) method used in geological correlation of Devonian rocks from Anti-Atlas Morocco. Amer. Assoc.

Petrol. Geol. Bull. 83, 1119-1134.[3] Rudman, A.J., Lankston, R.W, 1973. Stratigraphic Correlation of Well Logs by Computer Techniques.

AAPG Bulletin, 57, 3: 577 - 588.

[4] Smith, T.F., Waterman, M.S., 1980. New Stratigraphic Correlation Techniques. The Journal of

Geology, 88, 4: 451-457.

[5] Hladil, J., Vondra, M., Cejchan, P., Vich, R., Koptikovi, L., Slavik, L. , 2010. The dynamic

time-warping approach to comparison of magnetic susceptibility logs and application to Lower Devonian

calciturbidites (Prague Synform, Bohemian Massif). Geologica Belgica, 13/4: 385-406.

[6] Torrence, C., Compo, G.P., 1998. A Practical Guide to Wavelet Analysis. MS. Program in

Atmospheric and Oceanic Sciences, University of Colorado, Boulder, Colorado.

[7] Koptikova, L. (submitted) Precise position of the Basal Choteevent and evolution of sedimentaryenvironment close above the Lower-Middle Devonian boundary: magnetic susceptibility, gamma-ray

spectrometric, lithological and geochemical record in Prague Synform (Czech Republic). , Palaeogeogr.

Palaeoclimatol. Palaeoecol.

*Projects: IAA300130702 and IGCP 580.


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Abstract -15

Cambrian-Ordovician Petrographic Facies of Walidiala Valley (Eastern

Senegal, West Africa)

M.B. Diouf

Dpartement de Gologie - Facult des Sciences et Techniques - Universit Cheikh Anta DIOP -

Dakar Sngal

The oldest sedimentary outcrops in Senegal are known in the East. There are facies of

upper Proterozoic to lower Paleozoic in the group of Mali, a glacial and postglacial

succession of Madina Kouta basin.

The Paleozoic formations are generally dated from the Cambrian-Ordovician on the basis

of shell fragments and molds of various invertebrates (gastropods, echinoderm spicules,benthic foraminifera, brachiopods). They consist of argillite and siltstone with gradual

silicifications passing obliquely to stratified quartzitic sandstone, microconglomeratic at

the base, less coarser at the top. The grains, moderately worn and relatively poorly sorted,

are caught in a secondary quartz cement replacing an original silty and oxidized matrix.

Above, chemical facies, dolomite and chert, cap the formation. Dolomite is locally silty,

microcrystalline, brecciated, with inclusions of pebbles (diamictic aspect), crossed by

chert veinlets. Dolomite is a dolospar compact brownish mass equigranular with

persistence of some micritic zones. This dolosparite consists of rhombs of

recrystallization associated with chalcedony, locally recrystallized in quartz.

The observed microfacies evidence a gradual evolution from a glacial to periglacial

environment to a fluvio-marine to marine environment. The different steps of this

evolution need to be dated.


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Abstract -16

Frequency dependent magnetic susceptibility as a perspective magnetic

tool: case study from alluvial deposits of River Nile

L. Lisa*, P. Lisy

1, M. Chadima

1, 2, V. Cilek

1, L. Sukova

3


([email protected])

2 Agico, Inc., Jecna 29a, CZ-62100 Brno, Czech Republic

3 Czech Institute of Egyptology, Charles University in Prague

In 2009, the Czech Institute of Egyptology, Charles University in Prague, and the

Institute of Geology, Academy of Sciences of the Czech Republic, carried out a

geoarchaeological research in the area of Sabaloka and the Sixth Nile Cataract in theSudan. The objective of the research was to attain better understanding of the history of

the Nile, climatic changes in the Holocene, and their impact both on the landscape and

the human society. One of the main tasks of the geoarchaeological research was to study

the sedimentological record of the Nile alluvial zone. The area included in the study

covered approximately 25 km of the Nile banks within the Sabaloka gorge and by the

Sixth Cataract. The alluvial plain within the gorge is generally 5 m above the water

level and at some places extends over tens of meters. Three, approximately 5 meters

high sections were cut into the banks of Nile River to be described from the point of

view of sedimentology and sampled for magnetic, geochemical and grain size studies in

the intervals of 10 cm or less according to the changes in lithology. Additional sampleswere taken for micromorphology and dating purposes.

Magnetic susceptibility was measured in two different operating frequencies using an

Agico MFK1-FA Kappabridge and the frequency dependent susceptibility was

calculated. The frequency dependent susceptibility enables to assess the amount of very

fine-grained superparamagnetic grains, which are supposed to be created during

pedogenetic processes. A simple correlation of magnetic susceptibility values with the

amount of frequency dependence is presented to distinguish between

provenance-related magnetic materials versus magnetic particles created subsequently

in-situ by pedogenetic processes. In Quaternary rock magnetic studies, the relatively

increased values of magnetic susceptibility measured in cross sections are

conventionally interpreted as an indicator of pedogenetic processes due to the changes

of climatic conditions. Such interpretations, however, may oversimplify the situation

since the variations in magnetic susceptibility may also reflect the variations in the

provenance of the sedimentary material along the studied cross section. In order to

confirm or rule out the contributions of pedogenetic processes magnetic susceptibility

values were correlated with grain size analyses and micromophological analyses.

The lithological variability of the Nile alluvial record allows us to test the information

value of frequency dependent magnetic susceptibility when combined with other

sedimentological tools. For the interpretations the studied sections have to be dividedinto homogenous parts reflecting the geological background and parts rich in

lithological changes. The frequency dependent magnetic susceptibility measured within


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the lithologically homogenous parts of the studied sections shows some kind of

dependence on the amounts of sand fraction. Sand rich material corresponds to the

relatively low values because of the higher presence of diamagnetic quartz grains. This

fact changes when sandy material is composed of darker heavy minerals concentrations.

The parts of the sections where the lithology alternates frequently show a slightly

different kind of dependence. Extremely high values of magnetic susceptibilitycorrespond to higher amounts of fraction below 0.01 mm which is interpreted according

to the sedimentological and micromorphological descriptions as rich in fine-grained

decomposed organic matter and soil particles. Layers where the organic matter is still

visible show low values of frequency dependent magnetic susceptibility, which should

mean that this material doesnt contain any soil particles rich in superparamagnetic

minerals.

* Projects: The geoarchaeological research in the area of Sabaloka and the Sixth Nile Cataract was

financed from the funds granted by the Grant Agency of the Charles University in Prague (project No.

259 025), by the Czech Academy of Sciences (international co-operation project No. M100130902) and

from the institutional project of the Institute of Geology ASCR, v.v.i. (project NO. Z 3013 0516).


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29

Abstract -17

Stromatoporoid growth-band series: optical logs as a scale for

magnetic susceptibility sampling

P. Lisy1*

, P. Cejchan1, A. Galle

1, J. Filip

1, L. Slavik

1, J. Hladil

1, O. Babek

2


([email protected])

2 Department of Geology, Palacky University, tr. 17. listopadu 12, 771 46 Olomouc, Czech

Republic

Skeleton. The annual increments in skeletons of Devonian stromatoporoids are 1-8

(3-6) mm thick. The primary elements calcified during several days were thin and/or

minute and correspond to immediate CaCO3 accretion rates 0.05-0.12 g/cm2

/yr. Theadditional skeletal (pseudoskeletal) precipitates, formed during c. tens of days,

increase this rate to 0.13-0.30 g/cm2/yr. Such accretion is one order of magnitude less

than for present scleractinians but up to several orders of magnitude more than for

present calcareous sponges. The obviously non-skeletal intraskeletal cements

contributed by 50-90% to the total mass of the end-diagenetic polycrystalline calcite

aggregates. The HMC compositions of primary skeletal elements with material-saving

building plans characterize the stromatoporoid skeletons as diagenetically soft. The

stromatoporoid banding seen in thin sections is characterized as very problematic

combined effects of structures, microstructures, alterations, cements and fills (a

complex mix of factors).

Optical data from polished sections. According to thousands of specimens assessed

worldwide, there are no doubts that more than 90% of backreef Givetian and Frasnian

stromatoporoids display a conspicuously developed seasonal bandings. This banding

seen on the surfaces of polished thick sections is not very dissimilar to that of the

recent scleractinian coralPorites, where the overall lightness variation chiefly relates to

the difference between the zones of rapid growth slow growth. In stromatoporoids, the

slow growth intervals may quite commonly terminate with breaks that are connected

with reduced and then again expanded growth surface (rugged margins of domical or

protracted bulbous str-s). The overall lightness is documented by standard imaging

(diffuse white-light source, reflected light). Automated spectral reflectance mapping is a

promising method to solve above mentioned mix of factors.

Basic processing of the data. The averaging along with any growth surface is

performed by transformation (2D deformation) of 1-3 cm wide segments of annual

increments into rectangular artefacts. The techniques respect also the inner

disproportions. Correction for true thickness is derived using the polished prisms cut

from the stromatoporoid skeletons between the growth nucleus and the terminal surface.

In the next step, the linear (horizontal) averaging of the signal is carried out. These

laterally averaged results calculated from the original reflected light map view are

mostly presented as logs in grey scale, whereas spectrometric are used forcomplementary analyses. For visualization purposes, the grey-tone stripes or curves are

often used.


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Standard relationships to material. The deeper insight into principles of the reflection

light image of the low skeletal density but light coloured bands (LDLBs) and high

skeletal density but dark coloured bands (HDDBs) shows that the refracted/reflected

light intensity has the primary control as follows. LBs: The recrystallized low density

skeletal structures preserve the relicts after the primary skeletal elements as fine

crystalline, pure-calcite, high-reflectance crystalline aggregates with numerousinterconnected crystal defects. Separation between the structure closely around the

skeletal elements and cements in chambers is good. The overall reflectance increases

with degree of this separation when the skeletal elements are narrow, well spaced and

showing a brilliant refraction on crystals. DBs: The skeleton-cement recrystallizates

in HD-DBs replaced the micritic parts of the dense skeleton in more aggressive way.

The large crystals are dark. Seemingly surprising results, but this rule is already

known from e.g. Cenozoic coral bands. The inherited crystal defects show a

considerable degree of healing; reflecting defects are small and dilute dispersed.

Minute Corg-rich inclusions of low reflectance may slightly deepen the overall dull

effect.

Exceptions and their treatment. Of course, there are also some specific differences

which may occasionally modify or change this common parallel between the true

skeletal density and banding as recorded by means of reflected light intensity. These

differences are caused by diagenetic variation in the skeleton-cement systems as well as

late stages of rock recrystallization. Possibly the most different configurations were

found in whitish reef limestones where some stromatoporoids may have a minimum

amount of primary pigments in their HD bands. In this case, the refraction lightness

LB-DB scheme is inverted (!) so that the HD bands are lighter than the LD. However,

all these differences from the standard scheme can be corrected using the functions that

are empirically constructed according to true skeletal density measurements made

manually in the thin-sectioned nodes. Therefore, this does not represent a major

problem for the techniques of calibration.

Boundaries of sampling intervals. The definition of intervals for MS sampling must

consider a sufficient mass of a sample. Thus, the boundaries are standard placed at the

mean value levels within the steeper LB/DB, DB/LB gradients. The saw with small disc

is necessary for cutting of micro slabs from e.g. 1-3 mm thick layers; mass of micro

slabs per a band sample is usually 1-5 g. The increments thinner than LB, DB bands can

be sampled and measured with difficulties (due to predominance of diamagnetic calcite).

*Projects: IAA300130702 and IGCP 580.


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Abstract -18

Stable isotope variations (13

Ccarb, 13

Corg, 15

Norg) during the Late

Devonianpunctata Event in Western Canada Sedimentary Basin

M.G. Sliwinski1, M.T. Whalen

1, J.H. Payne,

1J. Day

2

1 Department of Geology & Geophysics, University of Alaska Fairbanks, Fairbanks, Alaska

99775, U.S.A.

2 Department of Geography-Geology, Illinois State University, Normal, IL 61790-4400, USA

In this contribution we report on stable isotope variations (13Ccarb,

13Corg, 15Norg)

during the Late Devonian (Mid-Frasnian)punctataEvent a prominent, yet short term

perturbation of the global carbon cycle with no associated extinction event. This data

supplements recent work on trace element, TOC and magnetic susceptibility (MS)variations during this time interval in the Western Canada Sedimentary Basin (liwiski

et al., 2010, GEOLOGICA BELGICA, 13/4: 459-482). From a methodological

viewpoint, it is assumed that multiple but independent geochemical proxies of

environmental and biotic changes will converge to produce an internally consistent

account of this event. We documented a ~2 positive 13Ccarbshift in the slope/basin

facies of the Miette carbonate platform, occurring at the transitans-punctata conodont

biozone boundary. This correlates with the initiation of the broader 13C excursion

observed in other basins worldwide. More commonly, the punctataEvent excursion is

reported as a positive (followed by a negative) shift of 4-5, occurring in four distinct

steps. Its magnitude likely related to location within the platform to basin transect, witha maximum 13C enrichment of ~6-7 reported from platform-top facies. Further, pre

excursion and post excursion isotopic baselines vary from basin to basin, indicating

that local and regional carbon cycle effects contribute significantly to the hitherto

generatedpunctataEvent records. A recent comprehensive state of the art reflection on

the current understanding of Late Devonian global events noted that despite a large

number of studies, the refined trends in biogeochemical cycling are poorly known at the

intra-zonal and inter-basinalscales. (Racki, 2005) Studies of the punctata Event have

addressed the first issue and strongly emphasized the need to search for and to

understand short-term global geochemical perturbations (at the intra-zonal level). This

is to better understand the global ecosystem and environmental changes of the Devonian,characterized by many extinction events, including the infamous and much studied

Frasnian-Fammenian biotic crisis (the fifth largest of the Phanerozoic. However, refined

trends at the inter-basinal scale are still lacking, but a increasingly consistent record is

slowly emerging. To date, however, no 13Corg records existed from western Laurussia

(but reported here) for inter-basinal comparisons with the records of Europe and China,

and sedimentary nitrogen isotope records have not been utilized at all in interpreting the

punctataEvent. We note here the existence of what we interpret to be a bioproductivity

event occurring near the transitans-punctata boundary, during which both organic and

inorganic C isotope values shift in tandem and become more 13C-enriched (a +13Corg

shift of ~3.75). At the same stratigraphic horizon, TOC values attain a maximum(up to 2.5 wt.%) and all suites of trace element proxies (detrital input, bioproductivity,


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bottom water redox) show prominent excursions above stratigraphic background levels.

The data was evaluated within 1) a regional sequence stratigraphic perspective

(revealing that trends are to some extent influenced by eustatic sea level and associated

climate change, as most proxies display an initial increase during lowstand and early

transgression of T-R cycle IIc1), and 2) the marine-terrestrial teleconnections model of

Algeo & Sheckler (1998), whereby the rise and expansion of arborescent vascular landplants (the first true forests results in a transient increase in pedogenesis and solute

delivery (hence biolimiting nutrients) to the oceans. The timing of the punctata Event

approximately coincides with the advent of archaeopterid forest expansion and rise to

dominance in the Frasnian-Fammenian age. This evolutionary event is speculated to

have amplified the detrital influx which was likely already elevated by conditions of sea

level lowstand, early transgression, episodes of mountain building and increased

weathering during Frasnian warming. Statistical correlations among proxies suggest that

changes in detrital input were the main driver of a bioproductivity increase. Elevated

organic matter export from the photic zone likely led to the deposition and later

preservation of organic-carbon rich facies under facilitated conditions of bottom wateroxygen depletion. Such a short term eutrophication of the regional environment may

have depleted the photic zone in biolimiting nitrate and phosphate, giving an

ecological advantage to N2 fixing autotrophs that help regulate the steady state of the

marine nitrogen cycle. The biomass of N2fixing microbes has a bulk 15N signature that

is only minimally fractioned relative to atmospheric nitrogen gas (~0 ). The observed

low nitrogen isotope values (-3.5-1) could be a reflection of such a biomass becoming

temporarily a significant/dominant fraction of organic matter exported to the sediment

during thepunctata Event.

Documents

2010 IGCP 580-Guilin, China