Henrik Blanchard - Profile on Academia.edu (original) (raw)

Papers by Henrik Blanchard

Can temperature assisted hydrostatic pressure reset the ambient TL of rocks? - A note on the TL of partially heated country rock from volcanic eruptions

ABSTRACT In the West Eifel Vocanic field of Germany, extensive fine grained tephra beds exist. Th... more ABSTRACT In the West Eifel Vocanic field of Germany, extensive fine grained tephra beds exist. These are derived from fragmentation of Lower Devonian siltstone. Analysis of fine grain TL and the IRSL of fine-grained tephra beds from independently dated tephra layers of 11 ka and ca. 20 ka suggested that their geological luminescence was reduced to near zero residual value during the eruption. This was despite the absence of any field evidence of heating above 400°C. We examined possible resetting mechanisms and suggest that thermally assisted hydrostatic pressure can reset the latent geological TL of country rock fragments during phreato-magmatic maar eruptions. We also provide first evidence of the suitability for TL dating of such material. As anomalous fading experiments have not been completed so far, we cannot give definitive TL ages here, but as the apparent ages are underestimated as compared to the control ages, complete zeroing is inferred. However a fortuitous combination of incomplete resetting and anomalous fading, that yields the expected De, though unlikely in view of long De plateaus arguing for complete resetting, cannot be entirely ruled out.

The Middle-Pleistocene (~300 ka) Rodderberg maar-scoria cone volcanic complex (Bonn, Germany): eruptive history, geochemistry, and thermoluminescence dating

International Journal of Earth Sciences, 2008

The Rodderberg volcanic complex (RVC) is located within the city limits of Bonn (Germany) approxi... more The Rodderberg volcanic complex (RVC) is located within the city limits of Bonn (Germany) approximately 20 km to the north of the Quaternary East Eifel Volcanic Field (EEVF). It is the product of intense phreatomagmatic volcanism forming a 90 m deep maar crater and strombolian eruptions. Deposit features indicate that the location of the vent(s) shifted from N to S during the

The effect of titanium on the partitioning behavior of high-field strength elements between silicates, oxides and lunar basaltic melts with applications to the origin of mare basalts

Chemical Geology, 2016

A specific feature of some basaltic lunar rocks is that their TiO2 contents can reach concentrati... more A specific feature of some basaltic lunar rocks is that their TiO2 contents can reach concentrations as high as 16 wt.%. The high-field strength elements (HFSE) group, which includes Ti, may provide valuable information of the processes that occurred in the lunar mantle to generate high-Ti mare basalts. To assess the effect of such high TiO2 concentrations on the partitioning of Zr, Hf, Nb, Ta, U, Th, Mo and W between major silicate and oxide phases and silicate melts, we present results from experiments at one atmosphere and 1100 °C–1305 °C, under controlled oxygen fugacity. With the exception of Nb, all DHFSEcpx/melt show a strong negative correlation with the TiO2 content of the silicate melt. Olivine/Silicate melt partition coefficients for Zr, Hf, Nb, Ta and Th decrease slightly from 0 to ca. 5 wt.% TiO2, above which they remain constant up to ca. 20 wt.% TiO2 in the silicate glass. In addition, redox sensitive elements, i.e. U, Mo, and W show clearly distinct DMsilicates/melt at different fO2, implying that these elements are relatively more compatible at reduced (ca. IW − 1.8) than at oxidized (FMQ and air) environments. Iron-rich and Mg-rich armalcolite show contrasting patterns of DMcrystal/melt, with the latter exhibiting slightly higher values of partition coefficient for all analyzed elements, except Th, which is equally incompatible in both end-members. Finally, the new dataset of DHFSEcrystal/melt was used to perform simple melting models of the lunar mantle cumulates. Results indicate that to reproduce the fractionation of W from the HFSE, as well as U and Th observed in lunar mare basalts, metal saturation and the presence of Fe–Ti oxides in the mantle sources is required.

Can temperature assisted hydrostatic pressure reset the ambient TL of rocks? - A note on the TL of partially heated country rock from volcanic eruptions

ABSTRACT In the West Eifel Vocanic field of Germany, extensive fine grained tephra beds exist. Th... more ABSTRACT In the West Eifel Vocanic field of Germany, extensive fine grained tephra beds exist. These are derived from fragmentation of Lower Devonian siltstone. Analysis of fine grain TL and the IRSL of fine-grained tephra beds from independently dated tephra layers of 11 ka and ca. 20 ka suggested that their geological luminescence was reduced to near zero residual value during the eruption. This was despite the absence of any field evidence of heating above 400°C. We examined possible resetting mechanisms and suggest that thermally assisted hydrostatic pressure can reset the latent geological TL of country rock fragments during phreato-magmatic maar eruptions. We also provide first evidence of the suitability for TL dating of such material. As anomalous fading experiments have not been completed so far, we cannot give definitive TL ages here, but as the apparent ages are underestimated as compared to the control ages, complete zeroing is inferred. However a fortuitous combination of incomplete resetting and anomalous fading, that yields the expected De, though unlikely in view of long De plateaus arguing for complete resetting, cannot be entirely ruled out.

Quaternary Geochronology, 2012

In the north of the island of Lanzarote (Canary Islands, Spain), two palaeosols from different si... more In the north of the island of Lanzarote (Canary Islands, Spain), two palaeosols from different sites were baked by overlying lava flows. Using red thermoluminescence (RTL) dating, late Middle Pleistocene ages were obtained, both varying around 170 ka thus indicating the simultaneity of the volcanic events. Blue thermoluminescence dating using different measuring techniques of the same sample material from one site (the Mála dune) yields somewhat lower ages, varying around 125 ka. However, this result is not in contradiction with the RTL age since anomalous fading was detected, expected to cause a significant underestimation of blue thermoluminescence results. Electron spin resonance dating from land snails overlying the lava flow yielded ages between 204 and 123 ka. Although this dispersion is rather large for material originating from the same stratigraphic horizon, it has to be taken into account that the amount of sample material and thus signal intensity was very low. Furthermore, small measured sample quantities are very vulnerable to dosimetric inhomogenities in the surrounding material, being a further source of uncertainty. Thus, these ESR ages bracketing the RTL age are a further support for a late Middle Pleistocene age of the lava flow. The Middle Pleistocene RTL ages of about 170 ka fill a conspicuous gap in the volcanic chronostratigraphy of Lanzarote, demonstrating that post-erosional volcanism on Lanzarote was obviously more continuous during the Middle and Late Quaternary than known before. Thus, these results demonstrate the potential of RTL and ESR dating to improve the timing of the Quaternary volcanism of the Canary Islands.

Earth and Planetary Science Letters, 2014

The timing of core formation is essential for understanding the early differentiation history of ... more The timing of core formation is essential for understanding the early differentiation history of the Earth and the Moon. Because Hf is lithophile and W is siderophile during metal-silicate segregation, the decay of 182 Hf to 182 W (half-life of 9 Ma) has proven to be a useful chronometer of core-mantle differentiation events. A key parameter for the interpretation of 182 Hf/ 182 W data is the Hf/W ratio of the primitive (i.e. undepleted) mantle. Since W is incompatible during mantle melting, its ratio relative to U and other similarly incompatible elements in basalts (e.g. Th, La) may be used as proxies for their mantle sources. However, the assumption that W and U are equally incompatible may be flawed for petrological systems that equilibrated over a large range of oxygen fugacity ( f O 2 ). Although W is typically perceived as being homovalent, evidence suggests that U is heterovalent over the range of f O 2 inferred for the silicate mantles of the Earth and the Moon. Here we report new partitioning data for W, U, high-field-strength elements (HFSE), and Th between clinopyroxene, orthopyroxene, olivine, plagioclase and silicate melt. In agreement with previous studies, we show that these elements behave as homovalent elements at f O 2 characteristic of Earth's upper mantle. However, both W and U become more compatible at low f O 2 , indicating a change in their redox state, with W becoming more compatible at progressively lower f O 2 . This result for W is particularly unexpected, because this element was thought to be hexavalent even at very low f O 2 . The much higher compatibility of W 4+ (the species inferred here at low f O 2 ) relative to W 6+ means that even a small fraction of W 4+ will have a significant effect on the overall compatibility of W. Our results imply that over the range of reducing conditions in which lunar differentiation is thought to have taken place (i.e. ∼IW-2 to IW-0.5), W is likely to become fractionated from U. When our partitioning data are applied to model the fractional crystallization of a lunar magma ocean, lunar trends for U/W, Hf/W and Th/W are well reproduced. The result of this model carries with it the implication that the Hf/W of the bulk silicate fractions that comprise the Earth and the Moon are virtually identical.

Quaternary Science Reviews, 2004

We would like to thank Carracedo et al. for their response to our earlier article, and shall do o... more We would like to thank Carracedo et al. for their response to our earlier article, and shall do our best to respond to both their queries and the various other communications we have received. We would like to commence by stating that we maintain our earlier stance concerning various as-yet unexplored inconsistencies in current interpretations of Lanzarote's Quaternary geological profile and occupational history. This paper is structured to address Carracedo et al.'s specific comments; however, we would firstly like to clarify some issues that appear to have been misunderstood by the authors.

Quaternary International, 2014

We present several approaches to directly date the prehistoric human activity of lighting a fire ... more We present several approaches to directly date the prehistoric human activity of lighting a fire at the Early Gravettian infant burial site of Krems-Wachtberg (Austria) by thermoluminescence (TL) methods. Blue thermoluminescence (B-TL) from polymineral fine grain and orange-red thermoluminescence (R-TL) from fine-grained quartz separates, both extracted from the baked loess immediately underlying the hearth were employed. The B-TL dating followed the "classic" multiple aliquot-additive dose (MAAD) protocol. For R-TL dating, the multiple aliquot-regenerative (MAR) and a shortened single-aliquotregeneration (SAR) protocol were tested. All thermoluminescence ages obtained agree within 1-s uncertainties and assign a weighted mean age of 33.9 AE 2.3 ka to the last use of the hearth and by inference to the infant burial. Anomalous fading is precluded due to the agreement of results from all luminescence protocols as well as with independent dating methods. The TL ages are consistent with calibrated radiocarbon ages on associated charcoal, OSL dating of the sediment deposition and with age estimates obtained by two magnetic dating approaches.

E&G Quaternary Science Journal, 2011

Kurzfassung Der mittelpleistozäne Vulkankomplex des Rodderbergs südlich von Bonn birgt vermutlich... more Kurzfassung Der mittelpleistozäne Vulkankomplex des Rodderbergs südlich von Bonn birgt vermutlich ein höchst wertvolles Klimaarchiv von regionaler und überregionaler Bedeutung. Er sitzt der aus dem älteren Mittelpleistozän stammenden "jüngeren Hauptterrasse" des Rheins auf. Sein zentraler Krater stellt eine bis heute geschlossene Hohlform dar, die noch fast vollständig von einem Wall aus Schlacken und Tephren umgeben ist. Eine im Jahre 2000 im Krater durchgeführte 55 m tiefe Kernbohrung (Rodderberg 1) förderte fast durchgängig feinkörnige Sedimente zutage, die im oberen Teil als Lösse und Lössderivate, im unteren Teil als Seesedimente angesprochen werden. Eine vom Leibniz-Institut für Angewandte Geophysik (LIAG) im Jahre 2008 niedergebrachte 69 m tiefe Schneckenbohrung erreichte in ca. 65 m Tiefe interglaziale Torfe. Festgestein wurde bisher nicht erreicht. Eine weitere Forschungsbohrung des LIAG ist für 2011 geplant. Der vorliegende Beitrag resümiert die bisherigen Ergebnisse zur Eruptionsgeschichte des Rodderberges und zu den Untersuchungen am Kerninhalt der Bohrung Rodderberg 1, zeigt bestehende Probleme auf und versucht, Anregungen für die weiteren Untersuchungen an der geplanten neuen Forschungsbohrung sowie in ihrem Umfeld zu geben.

Der Rodderberg-Krater bei Bonn

EG Quaternary Science Journal, 2011

Geochemical Perspectives Letters

We appreciate the comments by Yang et al. (2018) to our recent proposal (Ballhaus et al., 2017) t... more We appreciate the comments by Yang et al. (2018) to our recent proposal (Ballhaus et al., 2017) that high pressure and ultra-reduced minerals in ophiolites may form by lightning strikes. We have carried out additional experiments to address the issues raised by Yang et al. (2018). We maintain that the ultra-reduced phases in ophiolites are best explained as plasma precipitates generated by lightning strikes.

The luminescence dating laboratory at the University of Bonn: equipment and procedures

Page 1. Ancient TL Vol. 20 No 2 2002 53 The luminescence dating laboratory at the University of B... more Page 1. Ancient TL Vol. 20 No 2 2002 53 The luminescence dating laboratory at the University of Bonn: equipment and procedures B. Mauz*, T. Bode, E. Mainz, H. Blanchard, W. Hilger, R. Dikau and L. Zöller Geographisches ...

Middle Pleistocene volcanic activity dated by red thermoluminescence (RTL) - a case study from Lanzarote (Canary Islands)

On Lanzarote (Canary Islands) soils were baked by Quaternary lava flows. This offers the possibil... more On Lanzarote (Canary Islands) soils were baked by Quaternary lava flows. This offers the possibility to date phases of eruptive activity by red thermoluminescence (RTL). We dated soil material baked by two different lava flows originating from the "Las Calderetas de Guatiza" volcanic chain in the northeast of the island by RTL. Furthermore, three samples of Helicidae-mollusk shells overlying one of the lava flows (site Mála) were dated using electron spin resonance (ESR). RTL datings were carried out using quartz grains 63-200 µm from baked material that were originally brought by eolian transport from the nearby Saharan desert. It appears that in spite of a baking temperature < 550°C the RTL-signal was sufficiently annealed and thus dating by RTL was possible. RTL ages of ca. 170 ka show good agreement with each other, however, ESR ages are up to 40 % higher than the corresponding RTL age of the lava flow in Mála. Despite this disagreement these results demonstrate that eruptive activity of the volcanic chain occurred during the Middle Pleistocene rather than during the Early Holocene/Late Pleistocene as supposed based on geomorphologic features. Furthermore, they show that 14C-ages of mollusk shells originating from Mála are underestimating volcanic activity up to a factor of 10, a problem often recorded in arid areas. These results demonstrate the value of luminescence and ESR datings on the semi arid Eastern Canary Islands. The successful dating of lava-baked soils on Lanzarote by RTL thus offers the possibility to further investigate the yet fragmentary Middle and Late Quaternary eruptive history of these islands.

EG Quaternary Science Journal, 2009

Abstract. Middle and Upper Quaternary volcanic events are often difficult to date, in particular ... more Abstract. Middle and Upper Quaternary volcanic events are often difficult to date, in particular when minerals suitable for 40Ar/39Ar-dating are missing. Here, we present first tests of a newly developed technique to use the thermoluminescence (TL) of maar tephra and crustal xenoliths for dating the eruption event. We take into consideration that resetting of the latent geological TL of country rock fragments during eruption may be incomplete. We therefore develop the “partial heat – longest plateau” (PHLP) technique to approach the inherited TL signal at eruption. This technique can overcome TL age overestimates due to incomplete zeroing, as is demonstrated for some eruptions in the Quaternary Eifel Volcanic Field, Germany, in the time range from 11 to 300 ka old. Although we avoid the often observed strong anomalous fading of volcanic feldspars and other volcanic minerals by using heated country rock xenoliths, we still face the problem of longer-term anomalous fading which may be...

Geochemical Perspectives Letters, Nov 1, 2017

Since ultra-high pressure (UHP) minerals have been discovered in ophiolites from Tibet and the Po... more Since ultra-high pressure (UHP) minerals have been discovered in ophiolites from Tibet and the Polar Urals, it is speculated that the mantle sections of ophiolites may originate deep within the mantle. The UHP minerals are frequently found together with ultra-reduced silicides, carbides, and nitrides. Consequently, it is argued that the deep mantle, or at least domains within it, must be highly reduced, so reduced that practically all transition elements at depth are present in the metallic state. We find it problematic to rewrite the history of ophiolite complexes based on these observations and suggest we should search for alternative and more realistic modes of origin. Electric discharge experiments at >6000 K reported here show that the UHP and highly reduced phase assemblages may precipitate from plasmas. We argue that the mineral assemblages may originate by lightning strikes. As such, they may not record the origin and emplacement history of the mantle lithologies within which they occur.

Can temperature assisted hydrostatic pressure reset the ambient TL of rocks? - A note on the TL of partially heated country rock from volcanic eruptions

ABSTRACT In the West Eifel Vocanic field of Germany, extensive fine grained tephra beds exist. Th... more ABSTRACT In the West Eifel Vocanic field of Germany, extensive fine grained tephra beds exist. These are derived from fragmentation of Lower Devonian siltstone. Analysis of fine grain TL and the IRSL of fine-grained tephra beds from independently dated tephra layers of 11 ka and ca. 20 ka suggested that their geological luminescence was reduced to near zero residual value during the eruption. This was despite the absence of any field evidence of heating above 400°C. We examined possible resetting mechanisms and suggest that thermally assisted hydrostatic pressure can reset the latent geological TL of country rock fragments during phreato-magmatic maar eruptions. We also provide first evidence of the suitability for TL dating of such material. As anomalous fading experiments have not been completed so far, we cannot give definitive TL ages here, but as the apparent ages are underestimated as compared to the control ages, complete zeroing is inferred. However a fortuitous combination of incomplete resetting and anomalous fading, that yields the expected De, though unlikely in view of long De plateaus arguing for complete resetting, cannot be entirely ruled out.

The Middle-Pleistocene (~300 ka) Rodderberg maar-scoria cone volcanic complex (Bonn, Germany): eruptive history, geochemistry, and thermoluminescence dating

International Journal of Earth Sciences, 2008

The Rodderberg volcanic complex (RVC) is located within the city limits of Bonn (Germany) approxi... more The Rodderberg volcanic complex (RVC) is located within the city limits of Bonn (Germany) approximately 20 km to the north of the Quaternary East Eifel Volcanic Field (EEVF). It is the product of intense phreatomagmatic volcanism forming a 90 m deep maar crater and strombolian eruptions. Deposit features indicate that the location of the vent(s) shifted from N to S during the

The effect of titanium on the partitioning behavior of high-field strength elements between silicates, oxides and lunar basaltic melts with applications to the origin of mare basalts

Chemical Geology, 2016

A specific feature of some basaltic lunar rocks is that their TiO2 contents can reach concentrati... more A specific feature of some basaltic lunar rocks is that their TiO2 contents can reach concentrations as high as 16 wt.%. The high-field strength elements (HFSE) group, which includes Ti, may provide valuable information of the processes that occurred in the lunar mantle to generate high-Ti mare basalts. To assess the effect of such high TiO2 concentrations on the partitioning of Zr, Hf, Nb, Ta, U, Th, Mo and W between major silicate and oxide phases and silicate melts, we present results from experiments at one atmosphere and 1100 °C–1305 °C, under controlled oxygen fugacity. With the exception of Nb, all DHFSEcpx/melt show a strong negative correlation with the TiO2 content of the silicate melt. Olivine/Silicate melt partition coefficients for Zr, Hf, Nb, Ta and Th decrease slightly from 0 to ca. 5 wt.% TiO2, above which they remain constant up to ca. 20 wt.% TiO2 in the silicate glass. In addition, redox sensitive elements, i.e. U, Mo, and W show clearly distinct DMsilicates/melt at different fO2, implying that these elements are relatively more compatible at reduced (ca. IW − 1.8) than at oxidized (FMQ and air) environments. Iron-rich and Mg-rich armalcolite show contrasting patterns of DMcrystal/melt, with the latter exhibiting slightly higher values of partition coefficient for all analyzed elements, except Th, which is equally incompatible in both end-members. Finally, the new dataset of DHFSEcrystal/melt was used to perform simple melting models of the lunar mantle cumulates. Results indicate that to reproduce the fractionation of W from the HFSE, as well as U and Th observed in lunar mare basalts, metal saturation and the presence of Fe–Ti oxides in the mantle sources is required.

Can temperature assisted hydrostatic pressure reset the ambient TL of rocks? - A note on the TL of partially heated country rock from volcanic eruptions

ABSTRACT In the West Eifel Vocanic field of Germany, extensive fine grained tephra beds exist. Th... more ABSTRACT In the West Eifel Vocanic field of Germany, extensive fine grained tephra beds exist. These are derived from fragmentation of Lower Devonian siltstone. Analysis of fine grain TL and the IRSL of fine-grained tephra beds from independently dated tephra layers of 11 ka and ca. 20 ka suggested that their geological luminescence was reduced to near zero residual value during the eruption. This was despite the absence of any field evidence of heating above 400°C. We examined possible resetting mechanisms and suggest that thermally assisted hydrostatic pressure can reset the latent geological TL of country rock fragments during phreato-magmatic maar eruptions. We also provide first evidence of the suitability for TL dating of such material. As anomalous fading experiments have not been completed so far, we cannot give definitive TL ages here, but as the apparent ages are underestimated as compared to the control ages, complete zeroing is inferred. However a fortuitous combination of incomplete resetting and anomalous fading, that yields the expected De, though unlikely in view of long De plateaus arguing for complete resetting, cannot be entirely ruled out.

Quaternary Geochronology, 2012

In the north of the island of Lanzarote (Canary Islands, Spain), two palaeosols from different si... more In the north of the island of Lanzarote (Canary Islands, Spain), two palaeosols from different sites were baked by overlying lava flows. Using red thermoluminescence (RTL) dating, late Middle Pleistocene ages were obtained, both varying around 170 ka thus indicating the simultaneity of the volcanic events. Blue thermoluminescence dating using different measuring techniques of the same sample material from one site (the Mála dune) yields somewhat lower ages, varying around 125 ka. However, this result is not in contradiction with the RTL age since anomalous fading was detected, expected to cause a significant underestimation of blue thermoluminescence results. Electron spin resonance dating from land snails overlying the lava flow yielded ages between 204 and 123 ka. Although this dispersion is rather large for material originating from the same stratigraphic horizon, it has to be taken into account that the amount of sample material and thus signal intensity was very low. Furthermore, small measured sample quantities are very vulnerable to dosimetric inhomogenities in the surrounding material, being a further source of uncertainty. Thus, these ESR ages bracketing the RTL age are a further support for a late Middle Pleistocene age of the lava flow. The Middle Pleistocene RTL ages of about 170 ka fill a conspicuous gap in the volcanic chronostratigraphy of Lanzarote, demonstrating that post-erosional volcanism on Lanzarote was obviously more continuous during the Middle and Late Quaternary than known before. Thus, these results demonstrate the potential of RTL and ESR dating to improve the timing of the Quaternary volcanism of the Canary Islands.

Earth and Planetary Science Letters, 2014

The timing of core formation is essential for understanding the early differentiation history of ... more The timing of core formation is essential for understanding the early differentiation history of the Earth and the Moon. Because Hf is lithophile and W is siderophile during metal-silicate segregation, the decay of 182 Hf to 182 W (half-life of 9 Ma) has proven to be a useful chronometer of core-mantle differentiation events. A key parameter for the interpretation of 182 Hf/ 182 W data is the Hf/W ratio of the primitive (i.e. undepleted) mantle. Since W is incompatible during mantle melting, its ratio relative to U and other similarly incompatible elements in basalts (e.g. Th, La) may be used as proxies for their mantle sources. However, the assumption that W and U are equally incompatible may be flawed for petrological systems that equilibrated over a large range of oxygen fugacity ( f O 2 ). Although W is typically perceived as being homovalent, evidence suggests that U is heterovalent over the range of f O 2 inferred for the silicate mantles of the Earth and the Moon. Here we report new partitioning data for W, U, high-field-strength elements (HFSE), and Th between clinopyroxene, orthopyroxene, olivine, plagioclase and silicate melt. In agreement with previous studies, we show that these elements behave as homovalent elements at f O 2 characteristic of Earth's upper mantle. However, both W and U become more compatible at low f O 2 , indicating a change in their redox state, with W becoming more compatible at progressively lower f O 2 . This result for W is particularly unexpected, because this element was thought to be hexavalent even at very low f O 2 . The much higher compatibility of W 4+ (the species inferred here at low f O 2 ) relative to W 6+ means that even a small fraction of W 4+ will have a significant effect on the overall compatibility of W. Our results imply that over the range of reducing conditions in which lunar differentiation is thought to have taken place (i.e. ∼IW-2 to IW-0.5), W is likely to become fractionated from U. When our partitioning data are applied to model the fractional crystallization of a lunar magma ocean, lunar trends for U/W, Hf/W and Th/W are well reproduced. The result of this model carries with it the implication that the Hf/W of the bulk silicate fractions that comprise the Earth and the Moon are virtually identical.

Quaternary Science Reviews, 2004

We would like to thank Carracedo et al. for their response to our earlier article, and shall do o... more We would like to thank Carracedo et al. for their response to our earlier article, and shall do our best to respond to both their queries and the various other communications we have received. We would like to commence by stating that we maintain our earlier stance concerning various as-yet unexplored inconsistencies in current interpretations of Lanzarote's Quaternary geological profile and occupational history. This paper is structured to address Carracedo et al.'s specific comments; however, we would firstly like to clarify some issues that appear to have been misunderstood by the authors.

Quaternary International, 2014

We present several approaches to directly date the prehistoric human activity of lighting a fire ... more We present several approaches to directly date the prehistoric human activity of lighting a fire at the Early Gravettian infant burial site of Krems-Wachtberg (Austria) by thermoluminescence (TL) methods. Blue thermoluminescence (B-TL) from polymineral fine grain and orange-red thermoluminescence (R-TL) from fine-grained quartz separates, both extracted from the baked loess immediately underlying the hearth were employed. The B-TL dating followed the "classic" multiple aliquot-additive dose (MAAD) protocol. For R-TL dating, the multiple aliquot-regenerative (MAR) and a shortened single-aliquotregeneration (SAR) protocol were tested. All thermoluminescence ages obtained agree within 1-s uncertainties and assign a weighted mean age of 33.9 AE 2.3 ka to the last use of the hearth and by inference to the infant burial. Anomalous fading is precluded due to the agreement of results from all luminescence protocols as well as with independent dating methods. The TL ages are consistent with calibrated radiocarbon ages on associated charcoal, OSL dating of the sediment deposition and with age estimates obtained by two magnetic dating approaches.

E&G Quaternary Science Journal, 2011

Kurzfassung Der mittelpleistozäne Vulkankomplex des Rodderbergs südlich von Bonn birgt vermutlich... more Kurzfassung Der mittelpleistozäne Vulkankomplex des Rodderbergs südlich von Bonn birgt vermutlich ein höchst wertvolles Klimaarchiv von regionaler und überregionaler Bedeutung. Er sitzt der aus dem älteren Mittelpleistozän stammenden "jüngeren Hauptterrasse" des Rheins auf. Sein zentraler Krater stellt eine bis heute geschlossene Hohlform dar, die noch fast vollständig von einem Wall aus Schlacken und Tephren umgeben ist. Eine im Jahre 2000 im Krater durchgeführte 55 m tiefe Kernbohrung (Rodderberg 1) förderte fast durchgängig feinkörnige Sedimente zutage, die im oberen Teil als Lösse und Lössderivate, im unteren Teil als Seesedimente angesprochen werden. Eine vom Leibniz-Institut für Angewandte Geophysik (LIAG) im Jahre 2008 niedergebrachte 69 m tiefe Schneckenbohrung erreichte in ca. 65 m Tiefe interglaziale Torfe. Festgestein wurde bisher nicht erreicht. Eine weitere Forschungsbohrung des LIAG ist für 2011 geplant. Der vorliegende Beitrag resümiert die bisherigen Ergebnisse zur Eruptionsgeschichte des Rodderberges und zu den Untersuchungen am Kerninhalt der Bohrung Rodderberg 1, zeigt bestehende Probleme auf und versucht, Anregungen für die weiteren Untersuchungen an der geplanten neuen Forschungsbohrung sowie in ihrem Umfeld zu geben.

Der Rodderberg-Krater bei Bonn

EG Quaternary Science Journal, 2011

Geochemical Perspectives Letters

We appreciate the comments by Yang et al. (2018) to our recent proposal (Ballhaus et al., 2017) t... more We appreciate the comments by Yang et al. (2018) to our recent proposal (Ballhaus et al., 2017) that high pressure and ultra-reduced minerals in ophiolites may form by lightning strikes. We have carried out additional experiments to address the issues raised by Yang et al. (2018). We maintain that the ultra-reduced phases in ophiolites are best explained as plasma precipitates generated by lightning strikes.

The luminescence dating laboratory at the University of Bonn: equipment and procedures

Page 1. Ancient TL Vol. 20 No 2 2002 53 The luminescence dating laboratory at the University of B... more Page 1. Ancient TL Vol. 20 No 2 2002 53 The luminescence dating laboratory at the University of Bonn: equipment and procedures B. Mauz*, T. Bode, E. Mainz, H. Blanchard, W. Hilger, R. Dikau and L. Zöller Geographisches ...

Middle Pleistocene volcanic activity dated by red thermoluminescence (RTL) - a case study from Lanzarote (Canary Islands)

On Lanzarote (Canary Islands) soils were baked by Quaternary lava flows. This offers the possibil... more On Lanzarote (Canary Islands) soils were baked by Quaternary lava flows. This offers the possibility to date phases of eruptive activity by red thermoluminescence (RTL). We dated soil material baked by two different lava flows originating from the "Las Calderetas de Guatiza" volcanic chain in the northeast of the island by RTL. Furthermore, three samples of Helicidae-mollusk shells overlying one of the lava flows (site Mála) were dated using electron spin resonance (ESR). RTL datings were carried out using quartz grains 63-200 µm from baked material that were originally brought by eolian transport from the nearby Saharan desert. It appears that in spite of a baking temperature < 550°C the RTL-signal was sufficiently annealed and thus dating by RTL was possible. RTL ages of ca. 170 ka show good agreement with each other, however, ESR ages are up to 40 % higher than the corresponding RTL age of the lava flow in Mála. Despite this disagreement these results demonstrate that eruptive activity of the volcanic chain occurred during the Middle Pleistocene rather than during the Early Holocene/Late Pleistocene as supposed based on geomorphologic features. Furthermore, they show that 14C-ages of mollusk shells originating from Mála are underestimating volcanic activity up to a factor of 10, a problem often recorded in arid areas. These results demonstrate the value of luminescence and ESR datings on the semi arid Eastern Canary Islands. The successful dating of lava-baked soils on Lanzarote by RTL thus offers the possibility to further investigate the yet fragmentary Middle and Late Quaternary eruptive history of these islands.

EG Quaternary Science Journal, 2009

Abstract. Middle and Upper Quaternary volcanic events are often difficult to date, in particular ... more Abstract. Middle and Upper Quaternary volcanic events are often difficult to date, in particular when minerals suitable for 40Ar/39Ar-dating are missing. Here, we present first tests of a newly developed technique to use the thermoluminescence (TL) of maar tephra and crustal xenoliths for dating the eruption event. We take into consideration that resetting of the latent geological TL of country rock fragments during eruption may be incomplete. We therefore develop the “partial heat – longest plateau” (PHLP) technique to approach the inherited TL signal at eruption. This technique can overcome TL age overestimates due to incomplete zeroing, as is demonstrated for some eruptions in the Quaternary Eifel Volcanic Field, Germany, in the time range from 11 to 300 ka old. Although we avoid the often observed strong anomalous fading of volcanic feldspars and other volcanic minerals by using heated country rock xenoliths, we still face the problem of longer-term anomalous fading which may be...

Geochemical Perspectives Letters, Nov 1, 2017

Since ultra-high pressure (UHP) minerals have been discovered in ophiolites from Tibet and the Po... more Since ultra-high pressure (UHP) minerals have been discovered in ophiolites from Tibet and the Polar Urals, it is speculated that the mantle sections of ophiolites may originate deep within the mantle. The UHP minerals are frequently found together with ultra-reduced silicides, carbides, and nitrides. Consequently, it is argued that the deep mantle, or at least domains within it, must be highly reduced, so reduced that practically all transition elements at depth are present in the metallic state. We find it problematic to rewrite the history of ophiolite complexes based on these observations and suggest we should search for alternative and more realistic modes of origin. Electric discharge experiments at >6000 K reported here show that the UHP and highly reduced phase assemblages may precipitate from plasmas. We argue that the mineral assemblages may originate by lightning strikes. As such, they may not record the origin and emplacement history of the mantle lithologies within which they occur.