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Journal ArticleDOI

Laghi di Monticchio (Southern Italy, Region Basilicata): genesis of sediments—a geochemical study

01 Jul 2008-Journal of Paleolimnology (Springer Netherlands)-Vol. 40, Iss: 1, pp 529-556

Abstract: The sedimentation record of Lago Grande di Monticchio (LGM) is one of the most prominent paleoclimatic archives in the on-glaciated areas of Europe. However, the modern lake system has never been the subject of intense limnological studies. On the basis of hydrochemical water profiles, detailed investigations of sediment short cores and in situ pore water profiles from the littoral to the profundal zone, we elucidate spatial variations of sediment genesis within the lake basin and the importance of various depth sections for the lake's internal nutrient cycling. Sediments from the smaller meromictic Lago Piccolo di Montichio are discussed as a reference. Our study demonstrates: (i) distinctly higher sediment accumulation for the centre of the lake basin by focussing of the settling particle flux; (ii) decline of carbonate from the littoral to the profundal zones; (iii) nonsynchronous change of calcite net-accumulation for various water depths; (iv) exceptionally high cation release from sediments covering the steeply inclining sector of the lake basin; (v) relatively constant dissolved silica concentrations in the pore waters (SiO2 *42 mg/l) independent of water depth and sediment composition; (vi) influx of oxygen-bearing groundwater into the anoxic hypolimnion after heavy rainfall and the associated precipitation of Fe-oxihydroxides; (vii) higher release of NH4 by anaerobic degradation of organic matter at a water depth of 23 m than for sediments at a maximum water depth of 32 m, whereby the latter reflects the importance of seasonal sediment re-oxidation for anaerobic degradation of organic debris; (viii) although seasonal reoxidation of sediments from various water depths is quite different, Oxygen Index values of LGM sediments fall in a small range, which reflects rapid microbial consumption of seasonally re-generated easily bio-degradable organic molecules.
Topics: Profundal zone (57%), Hypolimnion (56%), Sediment (54%), Sedimentation (51%), Dissolved silica (51%)

Summary (3 min read)

Introduction

  • Sediment from Lago Grande di Monticchio (LGM, Fig. 1a–c) represents one of the most prominent European terrestrial paleoenvironmental archives with a continuous 100 kyr record spanning the Eem interglacial to the modern industrial period (Allen et al. 1999).
  • Contributions to local vegetation development as a mirror of paleoclimate change have been given by Watts (1985), Watts et al. (1996a, b, 2000), Huntley et al. (1999) and Allen et al. (2000, 2002).
  • Still missing is a deeper understanding of sediment genesis in LGM, which constrains paleoclimatic interpretation of geochemical and geomagnetic sediment profiles that are partially based on sediment cores from various water depths (see contributions by Creer and Morris 1996; Brandt et al. 1999).
  • The oldest volcanic products of the Monte Vulture are the Foggianello sub-unit deposits of Fara d’Olivo ignimbrite (Crisci et al. 1983).
  • The lake level of LGM shows seasonal fluctuations, with high levels in early spring (pers. comm., local residents 1994).

Sampling

  • On 22 August 1994 and 19 September 1994, temperature profiles of the water column were taken at the deepest part of both lakes.
  • Divers placed dialysis cells along a transect (Fig. 1b) in the surface sediments of LGM at various water depths such that the uppermost dialysis chamber fit with the sediment/water interface (see Schwedhelm et al. 1988 for cell construction).
  • The vertical distance between each chamber was 1 cm with 2 chambers at each depth level.
  • Short gravity cores ( 70 cm) were taken from the centre of lake LPM and along a transect (Fig. 1b) from LGM using a Niemistö gravity corer (Niemistö 1974).
  • The cores were continuously sampled at 3 cm slices by vertical extrusion; sample slices were immediately stored in a refrigerated box.

Water samples

  • The determination of fluoride, chloride, nitrate and sulphate was carried out by ion exchange chromatography (DX 100, Dionex).
  • Soluble Reactive Phosphorus (SRP) and ammonium were determined colorimetrically (FIAS, Perkin Elmer) using the molybdenum-blue method for SRP measurements and spectro-photometry of an indicator solution after separation of NH3 through a Teflon membrane (for details see Müller et al. 1992).
  • Dissolved inorganic carbon (DIC) of lake water samples was measured coulometrically.
  • Dissolved silica and cations were measured sequentially by ICP-AES (ARL 35000).
  • Temperature profiles of the lakes were taken by means of a water-tight single channel logger with an integrated thermistor temperature sensor (XL-100) manufactured by Richard Brancker Research, Canada.

Sediment samples

  • Sediment samples were frozen on return to the laboratory (1–2 days after sampling) and later freeze-dried.
  • The total carbon and nitrogen were determined after thermal decomposition at 1,350°C in an oxygen-gas-flow by IR-spectrometry and heat-conductivity detection, respectively (CNS 2000, LECO).
  • Elemental sulphur was determined after methanol-extraction (reflux, 7 min) by reversed phase liquid chromatography (eluent: 80% methanol, column: C-18, UV-detection 254 nm, DX 100, Dionex, see Möckel 1984).
  • Lead-214 was typically measured at count rates between 200 and 800.
  • Detector efficiency calibration for 46.539 keV was based on αspectrometric measurements using a 208Po recovery spike.

Lake water characteristics

  • In the summer of 1994, LGM was characterized by high turbidity (Secchi-depth <30 cm) and elevated pH in the surface water (pH = 8.35, 18 September 1994, 18:30), whereas the epilimnion of LPM had clear water with high Secchi-depths (pH = 7.86, 19 September 1994, 10:00).
  • Increase of Ca and DIC in the hypolimnion of LGM towards the lake bottom reflects post-depositional dissolution of autochthonous carbonate.
  • LGM and LPM show unusually high Sr concentrations and low Ca/Sr and Na/Sr ratios (Sr: 0.6 mg/l, Ca/Sr: 75, Na/Sr: 60, Fig. 2e, i).
  • During summer stratification, the SO4 concentration had significantly decreased in the anoxic deep water, but increased again by the inflow of groundwater (Fig. 3i).
  • The LGM lake water is moderately mineralized, so the authors could not obtain hints for subsurface inflow of highly saline waters that could trigger development of meromictic conditions.

Radiometric data

  • Unsupported 210Pb in the upper 15 cm of the LPM core and in the LGM core from 4 m depth shows similar high activity values and a distinct decline in the upper sections of these cores (Fig. 4a–d, Table 1).
  • The 137Cs profiles confirm that sediment accumulation at the 23 m site distinctly exceeds that of the profundal LPM sediments and that of LGM sediments from the shallow water (Fig. 4e–h).
  • The initial unsupported 210Pb activity of 760 mBq/g calculated on the basis of CIC assumptions probably exceeds that of earlier sedimentation periods.
  • The geochemical signatures of deeper sediments at the 8 m depth, showing distinctly lower Al contents (Fig. 5g), could reflect the presence of minerogenic debris with a geochemical composition that completely differs from those of the other LGM cores.
  • They may also reflect in situ sulphide precipitation within discrete sulphate reduction zones and the diffusive flux of Fe dissolved in pore water towards these zones.

Pore water chemistry

  • Pore water profiles can be used to assess microbial activity within sediments and the diffusive exchange between sediments and the overlying water.
  • The pore water profile of the 12 m site is characterized by overall higher Ca and DIC concentrations and shows a distinct decline of the concentration gradients between 35 cm and the sediment water interface.
  • The NH4 pore water profile recovered from the 12 m depth shows a different pattern with a maximum at 42 cm and a concentration gradient towards the sediment/water boundary.
  • The SRP pore water profile reflects well the different phosphorus release at various depth levels.
  • Sediments of the smaller LPM show higher TOC/N values than LGM sediments (Fig. 5a).

Synopsis

  • (1) Sediments of LGM document gradually increasing contributions from dead planktonic matter in the course of the recent sedimentation history and show clear variations in their geochemical composition depending on water depth.
  • Autochthonous calcite is characterized by a distinctly higher Ca/Sr ratio than the coexisting lake water.
  • Relatively higher accumulation of macrophytic organic remnants and littoral CaCO3 does not counterbalance focussing of the particle flux towards the centre of the lake basin.
  • Re-precipitation of pore water dissolved Fe as Fe-oxihydroxide is accompanied by substantial co-precipitation of U and Mo. Enhanced chemical alteration in the steeply inclining sector of LGM is documented in pore water profiles from the 12 m site that show distinctly elevated Na, K, Mg, Ca, Mn and DIC concentrations with strong gradients towards the sediment/water interface.
  • (5) Silica pore water concentrations, which should largely originate from the post-depositional dissolution of biogenic opal, have a uniform value of ca. 42 mg/l SiO2 in LGM sediments.

Figures

  • The basis of assumed values for porosity (ϕ) and density of the solid sediment (ρs).
  • The depth estimate for the year 1963 in core 6 m (b) was calculated on the basis of CRS assumptions minerogenic sediment constituent on CaCO3-free base for an assumed Al2O3 content of 15.6 wt% of the bulk siliciclastic sediment fraction (Al2O3 value for mean continental crust composition after Taylor (1964), see (g) for Al concentration data).
  • (h–l) Profiles of selected element ratios, characterizing the siliciclastic sediment fraction: LaN/TmN, ratio of Chondrite-normalized REE concentrations (used data for normalization from Taylor and McLennan (1985)).
  • Distinctly enhanced Fe/Al, U/Al and Mo/Al values in the profiles from the 8 m sampling site reflect intense chemical alteration and re-distribution of Fe, U and Mo. Increase of Fe/Al and Mo/Al in the LPM sediments coinciding with Stotal increase, (n) indicates sulphide-precipitation of Fe and Mo in the modern LPM, (m) excess.
  • Fe balanced for an assumed Fe/Al mass ratio of 0.9 for the minerogenic debris.

58.5 0.85 2.0 – −13 – 54

  • APorosity and density of solid sediments considered for lead-210 dating, given activity data related to 1 September 1994.

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Laghi di Monticchio (Southern Italy, Region Basilicata):
genesis of sediments-a geochemical study
Georg Schettler, Patrick Albéric
To cite this version:
Georg Schettler, Patrick Albéric. Laghi di Monticchio (Southern Italy, Region Basilicata): genesis of
sediments-a geochemical study. Journal of Paleolimnology, Springer Verlag, 2008, 40 (1), pp.529-556.
�10.1007/s10933-007-9180-4�. �insu-00252989�

Laghi di Monticchio (Southern Italy, Region Basilicata): genesis
of sediments—a geochemical study
Georg Schettler
1
and Patrick Albéric
2
(1) GeoForschungsZentrum Potsdam, Section Climate Dynamics and Sediments,
Telegrafenberg C328, 14473 Potsdam, Germany
(2) Institut des Sciences de la Terre d’Orléans (ISTO), UMR 6113 CNRS-Université
d’Orléans, Bâtiment Géosciences, BP 6759, Rue de St Amand, 45067 Orléans Cedex 2,
France
Abstract The sedimentation record of Lago Grande di Monticchio (LGM) is one of the most
prominent paleoclimatic archives in the non-glaciated areas of Europe. However, the modern
lake system has never been the subject of intense limnological studies. On the basis of
hydrochemical water profiles, detailed investigations of sediment short cores and in situ pore
water profiles from the littoral to the profundal zone, we elucidate spatial variations of
sediment genesis within the lake basin and the importance of various depth sections for the
lake’s internal nutrient cycling. Sediments from the smaller meromictic Lago Piccolo di
Montichio are discussed as a reference. Our study demonstrates: (i) distinctly higher sediment
accumulation for the centre of the lake basin by focussing of the settling particle flux; (ii)
decline of carbonate from the littoral to the profundal zones; (iii) non-synchronous change of
calcite net-accumulation for various water depths; (iv) exceptionally high cation release from
sediments covering the steeply inclining sector of the lake basin; (v) relatively constant
dissolved silica concentrations in the pore waters (SiO
2
~42 mg/l) independent of water depth
and sediment composition; (vi) influx of oxygen-bearing groundwater into the anoxic
hypolimnion after heavy rainfall and the associated precipitation of Fe-oxihydroxides; (vii)
higher release of NH
4
by anaerobic degradation of organic matter at a water depth of 23 m
than for sediments at a maximum water depth of 32 m, whereby the latter reflects the
importance of seasonal sediment re-oxidation for anaerobic degradation of organic debris;
(viii) although seasonal re-oxidation of sediments from various water depths is quite different,
Oxygen Index values of LGM sediments fall in a small range, which reflects rapid microbial
consumption of seasonally re-generated easily bio-degradable organic molecules.
Keywords Lacustrine sediments - Geochemistry - Genesis
Introduction
Sediment from Lago Grande di Monticchio (LGM, Fig. 1a–c) represents one of the most
prominent European terrestrial paleoenvironmental archives with a continuous 100 kyr record
spanning the Eem interglacial to the modern industrial period (Allen et al. 1999). During the
last decade, a reliable chronology for the LGM sedimentation record has been developed
based on varve counting, AMS
14
C-dating, and tephrochronostratigraphy (Newton and
Dugmore 1993; Zolitschka and Negendank 1993, 1996; Narcisi 1996; Huntley et al. 1999;
Wulf et al. 2004). Contributions to local vegetation development as a mirror of paleoclimate
change have been given by Watts (1985), Watts et al. (1996a, b, 2000), Huntley et al. (1999)
and Allen et al. (2000, 2002). Diatom assemblages in LGM sediments as a proxy for
paleoenvironmental change were investigated by Nimmergut et al. (1999). A pioneering
geochemical study of a 50 m sedimentation record from LGM was done by Robinson (1994).
Further geochemical sediment profiles were published by Creer and Morris (1996), Ramrath

et al. (1999) and Brauer et al. (2000). Still missing is a deeper understanding of sediment
genesis in LGM, which constrains paleoclimatic interpretation of geochemical and
geomagnetic sediment profiles that are partially based on sediment cores from various water
depths (see contributions by Creer and Morris 1996; Brandt et al. 1999).
Here, a study of the modern LGM, based on snapshots of thermal and chemical lake
stratification, in situ pore water profiles and investigation of short sediment cores taken along
a transect from the littoral zone to the centre of the lake during summer stratification, is
presented. The study was carried out to assess: (1) principal differences in sediment
characteristics at various water depths, (2) differences in sediment accumulation between the
shallow water area and the centre of the lake basin, (3) geochemical implications for
groundwater inflow, (4) post-depositional redistribution of chemical elements and (5) the
importance of various depth sections for the nutrient and sulphur cycle in LGM.
Geological setting and hydrological conditions
The Laghi Grande and Piccolo di Monticchio are maar lakes embedded in a collapsed
structure on the southwestern slopes of the Monte Vulture volcanic complex (Fig. 1c). The
suite of the local volcanic rocks is divided into two major units: the older Monte Vulture
complex and the younger Monticchio unit. The oldest volcanic products of the Monte Vulture
are the Foggianello sub-unit deposits of Fara d’Olivo ignimbrite (Crisci et al. 1983). The Fara
d’Olivo trachytic ignimbrite exhibits an age of 742 ± 11 kyr after Villa (1988). Buettner et al.
(2006) suggested an age of 740 ± 7 kyr for the lower and <740 kyr for the upper Fara d’Olivo
unit. The largest local volcanic rocks by volume are primary and epiclastic deposits of the
Barile unit. Volcanic products of this unit were ejected between ca. 673 and 610 kyr BP (see
Table 7-2 in Buettner et al. 2006 and references therein).
After a period of quiescence, the Monte Vulture volcano became dismembered by faulting
(Valle dei Greggi-Fosso del Corbo fault system). Volcanism resumed with volumetrically
subordinate eruptions assigned to the Monticchio unit (Laghi di Monticchio unit:
132 ± 12 kyr, Brocchini et al. 1994; 141 ± 11 kyr suggested by Buettner et al. 2006). Faulting
caused subsidence of the southern half of the Vulture complex and collapse of its
southwestern part. Eruptive activity of the Monticchio unit scattered along the active fault
systems and was dominantly linked to diametric structures, two of which are located under the
Monticchio Lakes (Giannandrea et al. 2006).
The igneous rocks of the Vulture complex comprise phonolites, tephri-phonolites, phonolitic-
foidites, and foidites (Principe et al. 2006 and references therein). Enhanced sulphur contents
associated with the occurrence of hauyne (Na,Ca)
4–8
[Al
6
Si
6
O
24
](SO
4
,S)
1–2
are peculiarities of
these rocks. High SO
4
contents of Vulture lavas are thought to be caused by magma
interaction with sedimentary SO
4
-rich brines from the basement of the volcano covering
Cretaceous to Pliocene sediments (La Volpe et al. 1984; De Fino et al. 1986). Substantial
hydrothermal calcite, gypsum, and anhydrite vein deposits were detected during explorations
in the hydrothermal fields of Tuscany and Latinum; Triassic marine evaporites are seen as the
major SO
4
source of these mineralizations (Marini and Chiodini 1994 and references therein)
and may also represent a major SO
4
source for hauyne-rich Vulture volcanites (see Table 1 in
De Fino et al. 1986 for hauyne contents). This interpretation is supported by relatively
positive δ
34
S values of metasomatic hauyne phenocrysts (+6.1, +6.6‰) from the Vulture
volcano (Cavarretta and Lombardi 1990). According to an alternative explanation, the
sulphate is primarily of magmatic origin: reduced sulphur became oxidized in the magma with

a high oxygen fugacity to SO
2
/SO
3
, and the escape of gaseous SO
2
/SO
3
left heavy
34
S behind
(see for detailed discussion Cavarretta and Lombardi 1990). The Laghi di Monticchio unit,
which is exposed in the western surroundings of LGM, involves a carbonatite-melilitite tuff
sequence abundant in mantle xenoliths (Stoppa and Principe 1998; Jones et al. 2000; Downes
et al. 2002). Formation of the maar lakes is associated with phreatomagmatic eruptions during
the final stage of volcanic activity.
The modern Lago Piccolo di Monticchio (LPM) has a maximum water depth of 38 m, a
surface area of 1.6 × 10
5
m
2
, and a water volume of 3.9 × 10
6
m
3
and receives sub-surface
inflow from a catchment area of 1.05 × 10
6
m
2
(Zolitschka and Negendank 1996). Lago
Piccolo di Monticchio is meromictic with a chemocline at about 13 m (Chiodini et al. 1997
and references therein). Monimolimnion waters in LPM are anoxic with high CO
2
content and
show a temperature increase with depth. Salinity increases to 1.8 g/l in the deepest part of the
lake basin (monitoring data 1995: Chiodini et al. 1997). The lake level of LPM is held
artificially 1 m above the lake level of LGM (~656 m asl).
The surface area of the dimictic LGM is 4.05 × 10
5
m
2
, and its water volume is 3.5 × 10
6
m
3
(Zolitschka and Negendank 1996). The lake receives sub-surface drainage from a catchment
of 3.04 × 10
6
m
2
, including that of LPM, and has one outlet. The morphology of the LGM
basin has been characterized by sonar measurements (Hansen 1993). Lago Grande di
Monticchio has an extended shallow area (Fig. 1b) with abundant submerged vegetation
(Ceratophyllum demersum) and a littoral fringe rich in Nympha alba and Polygonum
amphibum.
Mean annual precipitation (815 mm) is relatively high due to the elevation of the site (e.g.
Monte Vulture: 1,262 m asl), although a pronounced dry period commonly occurs in the
summer. The hillside is densely forested and dominated by Beech (Fagus sylvatica) and
Turkey Oak (Quercus cerris) (Watts et al. 1996b). A high percentage of precipitation does not
drain but undergoes evapotranspiration. For an assumed evapotranspiration of 80% in the
catchment, the above hydrological data suggest a water residence time of ~7 years for LGM.
Loosely deposited pyroclastics in the catchment of LGM favour the seepage of precipitation.
Drainage by surface runoff into the lakes, however, may occur during the melting of snow
when the top-soils are frozen.
The lake level of LGM shows seasonal fluctuations, with high levels in early spring (pers.
comm., local residents 1994). During late spring and summer, the lake level commonly
decreases by one to two metres. Water level increase is limited by a canal built by monks of
the monastery San Ippolito that was founded within the Piano Comune tuff ring depression in
AD 1059 and discharges Lago Grande waters into the river Ofanto. During the winter of
1993/1994, both lakes were ice-covered. A clearly visible terrace, ca. 5 m above the modern
lake level, indicates that the lake level was higher in the past. The lands surrounding Monte
Vulture are cultivated, especially for cereals.
Sampling
On 22 August 1994 and 19 September 1994, temperature profiles of the water column were
taken at the deepest part of both lakes. Divers placed dialysis cells along a transect (Fig. 1b) in
the surface sediments of LGM at various water depths such that the uppermost dialysis
chamber fit with the sediment/water interface (see Schwedhelm et al. 1988 for cell
construction). The vertical distance between each chamber was 1 cm with 2 chambers at each

depth level. At each cell site, water samples were taken approximately 0.5 m above the
surface sediment. To determine the amount of cations, an aliquot of the water sample was
membrane-filtered (0.45 μm) and stabilized with nitric acid. Upon removal by divers on 19
September 1994, the single dialysis chambers were immediately sampled with syringes in
7 ml polypropylene tubes with a screw closure, manufactured by Sarstedt (Germany). One
sample from each depth was stabilized by addition of 20 μl HNO
3
.
Short gravity cores (70 cm) were taken from the centre of lake LPM and along a transect
(Fig. 1b) from LGM using a Niemistö gravity corer (Niemistö 1974). The cores were
continuously sampled at 3 cm slices by vertical extrusion; sample slices were immediately
stored in a refrigerated box. Sediments from the deepest part of LGM had very high gas
contents (methane), precluding taking a core from the deepest part of LGM.
Analytical methods
Water samples
The determination of fluoride, chloride, nitrate and sulphate was carried out by ion exchange
chromatography (DX 100, Dionex). Soluble Reactive Phosphorus (SRP) and ammonium were
determined colorimetrically (FIAS, Perkin Elmer) using the molybdenum-blue method for
SRP measurements and spectro-photometry of an indicator solution after separation of NH
3
through a Teflon membrane (for details see Müller et al. 1992). Dissolved inorganic carbon
(DIC) of lake water samples was measured coulometrically. The DIC of pore water samples
was determined by a commercial laboratory (ANTEUM, Berlin) by adding a small sample
volume to phosphoric acid and performing IR-spectrometry of the released carbon dioxide
(TOC 5000, Shimadzu). Dissolved silica and cations were measured sequentially by ICP-AES
(ARL 35000). Temperature profiles of the lakes were taken by means of a water-tight single
channel logger with an integrated thermistor temperature sensor (XL-100) manufactured by
Richard Brancker Research, Canada.
Sediment samples
Sediment samples were frozen on return to the laboratory (1–2 days after sampling) and later
freeze-dried. The <185 μm fraction was separated from the freeze-dried material by sieving. It
comprised almost 100% of the total sample. After a HNO
3
/HClO
4
/HF/HCl-decomposition of
0.25 g solid sample, the determination of major and minor elements, including phosphorus
and sulphur, was carried out by sequential ICP-AES (ARL 35000) and external calibration.
Selected trace elements were measured by ICP-MS using a VG Plasma Quad PQ2+.
Beryllium-9,
115
In and
187
Re were used for internal standardization. The total analytical errors
for ICP-MS measurements were below ±10%. Inorganic carbon was measured
coulometrically after decomposition with hot phosphorus acid (Coulomat 702, Ströhlein). The
total carbon and nitrogen were determined after thermal decomposition at 1,350°C in an
oxygen-gas-flow by IR-spectrometry and heat-conductivity detection, respectively (CNS
2000, LECO). Organic carbon was calculated by difference using the total and inorganic
carbon results. Elemental sulphur was determined after methanol-extraction (reflux, 7 min) by
reversed phase liquid chromatography (eluent: 80% methanol, column: C-18, UV-detection
254 nm, DX 100, Dionex, see Möckel 1984). The chromatographic method enables the
detection of polysulphides and sulphur of various chain- and ring-size, respectively.
Octagonal ring-sized sulphur (S
8
) was the dominant sulphur modification in the examined
methanol-extracts. Only its peak area was considered for quantitative analyses of total
elemental sulphur.

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Journal ArticleDOI
Jacopo Cabassi1, Franco Tassi1, Orlando Vaselli1, Jens Fiebig2  +4 moreInstitutions (3)
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30 citations


Journal ArticleDOI
Abstract: . Sedimentation processes occurring in the most recent maar lake of the French Massif Central (Lake Pavin) are documented for the first time based on high resolution seismic reflection and multibeam bathymetric surveys and by piston coring and radiocarbon dating on a sediment depocentre developed on a narrow sub aquatic plateau. This new data set confirms the mid Holocene age of maar lake Pavin formation at 6970±60 yrs cal BP and highlights a wide range of gravity reworking phenomena affecting the basin. In particular, a slump deposit dated between AD 580–640 remoulded both mid-Holocene lacustrine sediments, terrestrial plant debris and some volcanic material from the northern crater inner walls. Between AD 1200 and AD 1300, a large slide scar mapped at 50 m depth also affected the southern edge of the sub aquatic plateau, suggesting that these gas-rich biogenic sediments (laminated diatomite) are poorly stable. Although several triggering mechanisms can be proposed for these prehistoric sub-aquatic mass wasting deposits in Lake Pavin, we argue that such large remobilisation of gas-rich sediments may affect the gas stability in deep waters of meromictic maar lakes. This study highlights the need to further document mass wasting processes in maar lakes and their impacts on the generation of waves, favouring the development of dangerous (and potentially deadly) limnic eruptions.

29 citations


Cites background from "Laghi di Monticchio (Southern Italy..."

  • ...For comparison, in the deepest part of the lake basin where focusing of settling particle fluxes may occur (Schettler and Alb́eric, 2008), the chronology established by Schettler et al. (2007) based on varve counting (cf. Fig....

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  • ...…et al., 1994; Siffedine et al., 1996; Oldfield, 1996; Brauer et al., 2008), but if some limnological studies describe the genesis of sediments (Schettler and Alb́eric, 2008), little is known in these volcanic environments about the triggering factors of gravity reworking phenomena and related…...

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Journal ArticleDOI
TL;DR: Analysis of δ18O of lake water and invertebrate remains, including head capsules of chironomid larvae and resting eggs of planktonic Cladocera, in surface sediments from 31 large, deep, and stratified lakes along a latitudinal transect through Europe found a systematic offset between the absolute δ 18O values of ch ironomids and cladocerans.
Abstract: An understanding of modern relationships between the stable oxygen isotope composition (δ18O) of lake water and aquatic invertebrates is essential for the interpretation of paleoclimate records based on δ18O of organic remains of these organisms. We analyzed δ18O of lake water and invertebrate remains, including head capsules of chironomid larvae and resting eggs (ephippia) of planktonic Cladocera, in surface sediments from 31 large, deep, and stratified lakes along a latitudinal transect through Europe. The δ18O values measured for both lake water and aquatic invertebrate remains were compared to estimated δ18O in precipitation. A strong linear relationship between mean annual air temperature and δ18O of precipitation was observed along the north–south transect (r = 0.97), whereas the relationship between precipitation δ18O and lake-water δ18O was weaker (r = 0.80). A strong positive correlation was observed between δ18O in lake water and aquatic invertebrates (r = 0.95 and 0.94 for chironomids and cladocerans, respectively). Although slopes of linear regressions between lake-water δ18O and δ18O of both aquatic invertebrate groups are similar, a systematic offset between the absolute δ18O values of chironomids and cladocerans was observed; chironomids were on average 2.4‰ heavier than Cladocera. We attribute this offset to differences in ecology, metabolism, and/or behavior between benthic chironomid larvae and planktonic Cladocera. δ18O records based on subfossil chironomid and cladoceran remains have the potential to quantitatively characterize past lake-water δ18O and, indirectly, past climatic changes.

20 citations


DOI
01 Jan 2009-
Abstract: iii

11 citations


Cites background from "Laghi di Monticchio (Southern Italy..."

  • ...Compared to other stratified lakes (e.g., Davison 1993; Schettler and Albéric 2008; Talling 1966; Talling and Talling 1965), Fe concentrations in the anoxic hypolimnion of Lake Challa (in August 2007) are relatively low....

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References
More filters

01 Jan 1985-
Abstract: This book describes the composition of the present upper crust, and deals with possible compositions for the total crust and the inferred composition of the lower crust. The question of the uniformity of crustal composition throughout geological time is discussed. It describes the Archean crust and models for crustal evolution in Archean and Post-Archean time. The rate of growth of the crust through time is assessed, and the effects of the extraction of the crust on mantle compositions. The question of early pre-geological crusts on the Earth is discussed and comparisons are given with crusts on the Moon, Mercury, Mars, Venus and the Galilean Satellites.

11,940 citations


"Laghi di Monticchio (Southern Italy..." refers methods in this paper

  • ...(h–l) Profiles of selected element ratios, characterizing the siliciclastic sediment fraction: LaN/TmN, ratio of Chondrite-normalized REE concentrations (used data for normalization from Taylor and McLennan (1985))....

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Journal ArticleDOI
Stuart Ross Taylor1Institutions (1)
Abstract: The rare earth pattern in sedimentary rocks is nearly constant and is considered to represent the relative abundances of these elements in the continental crust. This pattern is derived principally from mixing of basic and acidic igneous rock patterns. Preliminary calculations indicate that approximately equal contributions of basic and acid patterns are required to give the observed rare earth abundance pattern in sedimentary rocks. A table of element abundances in the continental crust, calculated on the basis of a 1:1 mixture of granite and basalt abundances, is presented. Attention is drawn to differences from previous estimates.

2,222 citations


Book ChapterDOI
Peter G. Appleby1Institutions (1)
01 Jan 2002-

1,378 citations


"Laghi di Monticchio (Southern Italy..." refers methods in this paper

  • ...The mean mass accumulation for the upper 37.5 cm of the 4 m core, calculated on the basis of CIC model assumptions (Appleby 2001 and references therein) and assumed data for porosity and mean density of the solid sediment (Table 1), accounts for 0.081 g/cm2 yr....

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Journal ArticleDOI
Eric Lafargue1, F. Marquis1, Daniel Pillot1Institutions (1)
Abstract: Successful petroleum exploration relies on detailed analysis of the petroleum system in a given area. Identification of potential source rocks, their maturity and kinetic parameters, and their regional distribution are best accomplished by rapid screening of rock samples (cores and/or cuttings) using the Rock-Eval apparatus. The technique has been routinely used for about fifteen years and has become a standard tool for hydrocarbon exploration. This paper describes how the new functions of the latest version of Rock-Eval (Rock-Eval 6) have expanded applications of the method in petroleum geoscience. Examples of new applications are illustrated for source rock characterization, reservoir geochemistry, and environmental studies, including quantification.

806 citations


"Laghi di Monticchio (Southern Italy..." refers methods in this paper

  • ...Basic RE parameters [Total Organic Carbon (TOC), Hydrogen Index (HI) and Oxygen Index (OI)] were calculated according to Espitalié et al. (1985) and Lafargue et al. (1998)....

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Journal ArticleDOI
Jean Espitalie1, G. Deroo1, F. Marquis1Institutions (1)
Abstract: Concue pour repondre aux besoins de l'exploration petroliere, la methode de pyrolyse Rock-Eval est maintenant largement utilisee. Elle fournit, en effet, et d'une facon rapide, differentes informations sur le contenu organique des roches, telles que le potentiel petrolier des series rencontrees, la nature des kerogenes, leur etat de maturation. En ce qui concerne le materiel, deux nouvelles versions ont ete mises au point a l'Institut Francais du Petrole (IFP) depuis l'apparition en 1977 des premiers appareils Rock-Eval : un Rock-Eval II completement automatise grâce a un microprocesseur et dote, en option, d'un module de dosage du carbone organique; un Rock-Eval III (Oil Show Analyzer) qui se distingue du precedent par le fait qu'il analyse separement le gaz et l'huile et qu'il effectue le dosage du carbone organique a la place du pic S3. En ce qui concerne l'interpretation de la methode, l'experience acquise tant par les applications aux bassins sedimentaires que par les etudes experimentales menees en laboratoire a permis de mieux connaitre les parametres utilises (pics S1, S2, S3, temperature de pyrolyse Tmax) a travers leurs variations et, de la, de mieux discerner les limites d'application de la methode. En ce qui concerne l'application de la methode, la representation verticale des resultats sous forme de logs geochimiques conduit a une interpretation a la fois efficace et pratique. Des abaques et des diagrammes de reference permettent de caracteriser les roches meres (potentiels petroliers, types de matiere organique, degre d'evolution, alterations. . . ) ainsi que les phenomenes de migration. L'etablissement de cartes geochimiques a l'echelle du bassin devient alors possible. Enfin la methode est sortie du domaine de l'exploration petroliere proprement dite pour trouver des applications a l'etude des charbons, des roches bitumineuses, des sediments recents et meme aux techniques du raffinage et de la recuperation secondaire des bruts.

723 citations


"Laghi di Monticchio (Southern Italy..." refers methods in this paper

  • ...Basic RE parameters [Total Organic Carbon (TOC), Hydrogen Index (HI) and Oxygen Index (OI)] were calculated according to Espitalié et al. (1985) and Lafargue et al. (1998)....

    [...]


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