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  • Elsevier  (20)
  • AGU (American Geophysical Union)  (10)
  • 2015-2019  (20)
  • 2005-2009  (10)
  • 1
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    Cryptotephra from Lipari Volcano in the eastern Gulf of Taranto (Italy) as a time marker for paleoclimatic studies (2018)
    Elsevier
    In:  Quaternary Research, 89 (2). pp. 520-532.
    Details
    Publication Date: 2021-02-08
    Description: We present the first tephroanalysis based on geochemical fingerprinting of volcanic glass shards from eastern Apulian shelf sediments in the Gulf of Taranto (Italy). High sedimentation rates in the gulf are ideal for high-resolution paleoclimate studies, which rely on accurate age models. Cryptotephrostratigraphy is a novel tool for the age assessment of marine sediment cores in the absence of discrete tephra layers. High-resolution quantitative analysis of glass shard abundance in the uppermost 45 cm of a gravity core identified two cryptotephras. Microprobe analysis of glass shards supported by an accelerator mass spectrometry 14C-based age model identified the pronounced primary cryptotephra at 36 cm bsf (below sea floor) as the felsic AD 776 Monte Pilato Eruption on the island of Lipari, whereas the thinner, mafic tephra layer at 1.5 cm bsf is associated with the AD 1944 eruption of Somma-Vesuvius. Identifying these tephra layers provides an additional, 14C-independent, stratigraphic framework for further paleoclimatic studies allowing us to link Mediterranean climate and hydrology to orbital variation and large-scale atmospheric processes. Our results underline the importance of qualitative tephrostratigraphy in a highly geodynamic region, where solely quantitative approaches have demonstrated to bear a high potential for false correlations between tephra layers and eruptions.
    Type: Article , PeerReviewed
    Format: text
    Format: other
    Format: other
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    DOI: 10.1017/qua.2018.2
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  • 2
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    Climate ultrastructure and aquatic community response to Heinrich Stadials (HS5a-HS1) in the continental northern Neotropics (2018)
    Elsevier
    In:  Quaternary Science Reviews, 197 . pp. 75-91.
    Details
    Publication Date: 2021-02-08
    Description: Highlights • Evaluation of environmental variability induced by Heinrich Stadials (HS5a-HS1) in continental northern Neotropical region. • Multiproxy evidence reveals mild temperature decreases and drastic fluctuations in precipitation during HSs. • Ultrastructure of HSs suggests individual environmental response of each Stadial making them contrasting from each other. • Most drastic climate changes induced by HSs exerted positive effects on diversity of aquatic communities. Abstract We reconstruct environmental conditions of the period 53-14 kyr BP in the continental northern Neotropical region. We evaluate in detail the magnitude of climatic fluctuations and their effects on aquatic communities during six Heinrich Stadials (HS1-HS5a), using sediments from Lake Petén Itzá, Guatemala, and a multiproxy approach. In Lake Petén Itzá typical Heinrich Stadials (HSs) are recorded in sediments as alternations of gypsum and clay, and abrupt changes in magnetic susceptibility, CaCO3 and biological compositions. This suggests that HSs were periods of hydrological unbalance, characterized by dry spells, punctuating the predominant humid conditions characterizing the period 53-14 kyr BP. The ultrastructure of HSs allows us to identify four different types of climatic conditions associated to HSs: 1) prevailing dry conditions but changing to humid (HS5, HS3); 2) predominantly humid conditions but changing to arid (HS2); 3) fluctuating humid-dry-humid (HS4, HS1); and 4) arid with high lake water conductivity (HS5a). The continuous presence of tropical ostracode species during HSs suggests that lake water temperatures were not drastically lowered. Ostracode-based transfer functions indicate that during HSs, epilimnetic water temperatures decreased by 1–3 °C compared to mean modern temperatures. Lake solute composition and conductivity were strongly affected by HSs. During HS5a and HS1 we estimate conductivity values 〉 800 μS cm−1. Diversity indices show significant differences (F5,70 = 3.74, p = 0.004) of ostracode species composition among HSs. Highest diversities occurred during HS5a, HS4 and HS1, which display greater climatic alterations than the other HSs. Fluctuating climates seem to have exerted positive effects on diversity of aquatic communities by producing an increase in habitat heterogeneity.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.quascirev.2018.07.015
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  • 3
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    Understanding Himalayan erosion and the significance of the Nicobar Fan (2017)
    Elsevier
    In:  Earth and Planetary Science Letters, 475 . pp. 134-142.
    Details
    Publication Date: 2020-12-23
    Description: Highlights • Sediment accumulation rates in Nicobar Fan abruptly increase 9.5 Ma. • Increased sediment flux to eastern Indian Ocean and restructuring of sediment routing. • Nicobar Fan holds significant record of Indian Ocean sedimentation in late Neogene. • Shillong Plateau and Indo–Burmese wedge uplift drive sediment south in late Miocene. A holistic view of the Bengal–Nicobar Fan system requires sampling the full sedimentary section of the Nicobar Fan, which was achieved for the first time by International Ocean Discovery Program (IODP) Expedition 362 west of North Sumatra. We identified a distinct rise in sediment accumulation rate (SAR) beginning ∼9.5 Ma and reaching 250–350 m/Myr in the 9.5–2 Ma interval, which equal or far exceed rates on the Bengal Fan at similar latitudes. This marked rise in SAR and a constant Himalayan-derived provenance necessitates a major restructuring of sediment routing in the Bengal–Nicobar submarine fan. This coincides with the inversion of the Eastern Himalayan Shillong Plateau and encroachment of the west-propagating Indo–Burmese wedge, which reduced continental accommodation space and increased sediment supply directly to the fan. Our results challenge a commonly held view that changes in sediment flux seen in the Bengal–Nicobar submarine fan were caused by discrete tectonic or climatic events acting on the Himalayan–Tibetan Plateau. Instead, an interplay of tectonic and climatic processes caused the fan system to develop by punctuated changes rather than gradual progradation.
    Type: Article , PeerReviewed
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    DOI: 10.1016/j.epsl.2017.07.019
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  • 4
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    Tephrostratigraphy and Provenance From IODP Expedition 352, Izu-Bonin arc: Tracing Tephra Sources and Volumes From the Oligocene to the Recent (2018)
    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 19 (1). pp. 150-174.
    Details
    Publication Date: 2021-03-19
    Description: Provenance studies of widely distributed tephras, integrated within a well-defined temporal framework, are important to deduce systematic changes in the source, scale, distribution and changes in regional explosive volcanism. Here, we establish a robust tephro-chronostratigraphy for a total of 157 marine tephra layers collected during IODP Expedition 352. We infer at least three major phases of highly explosive volcanism during Oligocene to Pleistocene time. Provenance analysis based on glass composition assigns 56 of the tephras to a Japan source, including correlations with 12 major and widespread tephra layers resulting from individual eruptions in Kyushu, Central Japan and North Japan between 115 ka and 3.5 Ma. The remaining 101 tephras are assigned to four source regions along the Izu-Bonin arc. One, of exclusively Oligocene age, is proximal to the Bonin Ridge islands; two reflect eruptions within the volcanic front and back-arc of the central Izu-Bonin arc, and a fourth region corresponds to the Northern Izu-Bonin arc source. First-order volume estimates imply eruptive magnitudes ranging from 6.3 to 7.6 for Japan-related eruptions and between 5.5 and 6.5 for IBM eruptions. Our results suggest tephras between 30 and 22 Ma that show a subtly different Izu-Bonin chemical signature compared to the recent arc. After a ∼11 m.y. gap in eruption, tephra supply from the Izu-Bonin arc predominates from 15 to 5 Ma, and finally a subequal mixture of tephra sources from the (palaeo)Honshu and Izu-Bonin arcs occurs within the last ∼5 Ma.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2017GC007100
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  • 5
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    The Malpaisillo Formation: A sequence of explosive eruptions in the mid to late Pleistocene (Nicaragua, Central America) (2018)
    Elsevier
    In:  Journal of Volcanology and Geothermal Research, 359 . pp. 47-67.
    Details
    Publication Date: 2021-02-08
    Description: The subduction-related volcanic front in Nicaragua consists of the Tertiary “Coyol” member in the eastern highlands and the Quaternary to recent volcanic arc within the Nicaraguan depression. Although the Holocene to recent explosive volcanism has been studied extensively no detailed work has been done on the products of explosive volcanism from Quaternary volcanic complexes comprising also the Malpaisillo and Monte Galán Calderas, the focus of this study. The 11 km-wide Malpaisillo Caldera and ~3.5 km-wide Monte Galán Caldera, located ~50 km northwest of Managua, are surrounded by tens of meters of rhyolitic tephras. These pyroclastic flow and fall deposits extend proximally at least 11 km to the southeast and 23 km to the southwest, with observed depositional thicknesses of 〉16 m for a single ignimbrite unit (or 〉25 m for the entire section). Distal deposits are found as far as 350 km offshore in the Pacific. At least twelve highly explosive large-volume eruptive phases with corresponding tephra deposits (LPT = La Paz Centro Tephra, PPT = Punta de Plancha Tephra, LCbT = Lower Chibola Tephra, GT = Guacucal Tephra, UCbT = Upper Chibola Tephra, FeT = La Fuente Tephra, ST = Sabanettas Tephra, MgT = Miralago Tephra, ToT = Tolapa Tephra, LMT, MMT, UMT = Lower, Middle, and Upper Maderas Negras Tephras) are distinguished based on geochemical correlations and similar depositional characteristics. Radiometric 40Ar/39Ar ages indicate that most activity related to the large Malpaisillo Caldera occurred between ~570 and ~420 ka. The large Pleistocene Malpaisillo and Monte Galán Calderas are characterized by a long-lived history and, if evolved, a distinctly alkaline (K2O = 2.3–3.8 wt%; Na2O = 4.0–4.9 wt%) geochemical signature compared to the other Nicaraguan tephra deposits. As a result, the previously defined Malpaisillo Formation has been considerably extended and revised. Our findings contribute to fill a considerable gap in the long-term eruptive history of Nicaraguan volcanoes, with prominent implications for volcanic hazard evaluation for Nicaragua.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.jvolgeores.2018.06.015
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  • 6
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    Application of a handheld X-ray fluorescence spectrometer for real-time, high-density quantitative analysis of drilled igneous rocks and sediments during IODP Expedition 352 (2017)
    Elsevier
    In:  Chemical Geology, 451 . pp. 55-66.
    Details
    Publication Date: 2020-02-06
    Description: Handheld energy dispersive portable X-ray spectrometers (pXRF) are generally designed and used for qualitative survey applications. We developed shipboard quantitative analysis protocols for pXRF and employed the instrument to make over 2000 individual abundance measurements for a selection of major and trace elements on over 1200 m of recovered core during the eight weeks of the International Ocean Discovery Program (IODP) Expedition 352 to the Izu-Bonin forearc. pXRF analytical performance, accuracy and precision were found to be the same on powdered rock samples and on freshly cut rock surfaces, and sample results were similar within error to measurements made via shipboard ICP-OES analysis save at low abundance levels for a few elements. Instrument performance was optimal for elements between Z = 19 and Z = 40, and the system yielded reproducible data for K, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Rb, Sr, and Zr on both powdered samples and rock surfaces. Working curves developed via pXRF measurement of a suite of geologic standard reference materials and well-characterized lavas permitted accurate quantitative measurements for many of the examined elements on both sample powders and rock surfaces. Although pXRF has been sporadically employed on previous cruises, Expedition 352 is the first time a detailed, high-density chemostratigraphy of recovered core samples was collected using pXRF measurements of rock core surfaces. These high-resolution data allowed the recognition of chemically distinct eruptive units in near real-time. The rapid identification of geochemical trends vastly improved our selection of samples for shipboard and shore-based analysis, permitted a more comprehensive interpretation of our Expedition results, and provided key decision-making information for drilling operations.
    Type: Article , PeerReviewed
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    DOI: 10.1016/j.chemgeo.2017.01.007
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  • 7
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    Evolution of magma chambers generating the phonolitic Cão Grande Formation on Santo Antão, Cape Verde Archipelago (2016)
    Elsevier
    In:  Journal of Volcanology and Geothermal Research, 327 . pp. 436-448.
    Details
    Publication Date: 2019-02-01
    Description: Highlights • Individual evolution of temporal and spatial co-existing magma suites • Determination of pre-eruptive magma chamber conditions of the Cão Grande Formation magma chambers • Cão Grande Formation phonolite magmas typically reach H2O-saturation prior to the eruption. Abstract The Cão Grande Formation (CGF) on the western plateau of Santo Antão is a sequence of four phonolitic tephras (Canudo Tephra, Cão Grande I Tephra, Cão Grande II Tephra and Furninha Tephra) produced by highly explosive eruptions that alternatingly originated from a basanitic - phonolitic and a nephelinitic - phonolitic magmatic system. Detailed stratigraphy and petrological investigations of each unit are used to demonstrate the unusual situation that two distinct highly evolved magmas differentiated contemporaneously in separate magmatic systems. Chemical thermobarometry suggests that both magmatic systems not only temporally co-existed, but also that their magma chambers resided close to each other at 7 to 16 km depth, beneath the western plateau of Santo Antão. However, the distinct melt and magma compositions indicate that both systems evolved independently. The only interaction between both magmatic systems was an injection of magma from the nephelinitic - phonolitic magmatic system into the Cão Grande II Tephra (CG II) phonolitic reservoir, which is associated to the basanitic - phonolitic magmatic system. Compositional zonations in the tephra deposits indicate that the eruptions of the CGF tapped stratified magma reservoirs that mainly resulted from crystal accumulation generating downward increasing magma density. However, the CG II tephras also show a significant gradient in melt (glass) compositions. Magmas of the Canudo Tephra (CT) and the Cão Grande I Tephra (CG I) were H2O-saturated and their eruptions were probably triggered by fluid overpressure in the magma chamber. On the other hand, the CG II magma was H2O-undersaturated; we therefore assume that the injection of the hot nephelinitic - phonolitic magma system-type melt/magma triggered the eruption. The zoned deposit of the Furninha Tephra (FT) indicates mafic magma replenishment into a phonolitic reservoir directly prior to the eruption, thus providing a probable triggering mechanism. The new magma chamber models and thermobarometric results for the four CGF units provide constraints for hazard assessments, because similar events may occur in the future considering the longevity of the CGF magma systems.
    Type: Article , PeerReviewed
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    DOI: 10.1016/j.jvolgeores.2016.09.016
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  • 8
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    South Asian monsoon history over the past 60 kyr recorded by radiogenic isotopes and clay mineral assemblages in the Andaman Sea (2015)
    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 16 (2). pp. 505-521.
    Details
    Publication Date: 2019-09-24
    Description: The Late Quaternary variability of the South Asian (or Indian) monsoon has been linked with glacial-interglacial and millennial scale climatic changes but past rainfall intensity in the river catchments draining into the Andaman Sea remains poorly constrained. Here we use radiogenic Sr, Nd, and Pb isotope compositions of the detrital clay-size fraction and clay mineral assemblages obtained from sediment core NGHP Site 17 in the Andaman Sea to reconstruct the variability of the South Asian monsoon during the past 60 kyr. Over this time interval eNd values changed little, generally oscillating between 27.3 and 25.3 and the Pb isotope signatures are essentially invariable, which is in contrast to a record located further northeast in the Andaman Sea. This indicates that the source of the detrital clays did not change significantly during the last glacial and deglaciation suggesting the monsoon was spatially stable. The most likely source region is the Irrawaddy river catchment including the Indo-Burman Ranges with a possible minor contribution from the Andaman Islands. High smectite/(illite1chlorite) ratios (up to 14), as well as low 87Sr/86Sr ratios (0.711) for the Holocene period indicate enhanced chemical weathering and a stronger South Asian monsoon compared to marine oxygen isotope stages 2 and 3. Short, smectite-poor intervals exhibit markedly radiogenic Sr isotope compositions and document weakening of the South Asian monsoon, which may have been linked to short-term northern Atlantic climate variability on millennial time scales.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2014GC005586
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  • 9
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    A 400-ka tephrochronological framework for Central America from Lake Petén Itzá (Guatemala) sediments (2016)
    Elsevier
    In:  Quaternary Science Reviews, 150 . pp. 200-220.
    Details
    Publication Date: 2019-02-01
    Description: Highlights • Dating 400 ka paleoclimate record of Neotropics. • Revision and new eruptive volumes for large Central American eruptions. • Age models for Petén Itzá sediments. • Linking lacustrine ash inventory to eruptions from Central America and Mexico. Abstract Lake Petén Itzá, northern Guatemala, lies within a hydrologically closed basin in the south-central area of the Yucatán Peninsula, and was drilled under the auspices of the International Continental Scientific Drilling Program (ICDP) in 2006. At 16°55′N latitude, the lake is ideally located for study of past climate and environmental conditions in the Neotropical lowlands. Because of its great depth (〉160 m), Lake Petén Itzá has a record of continuous sediment accumulation that extends well into the late Pleistocene. A key obstacle to obtaining long climate records from the region is the difficulty of establishing a robust chronology beyond ∼40 ka, the limit of 14C dating. Tephra layers within the Lake Petén Itzá sediments, however, enable development of age/depth relations beyond 40 ka. Ash beds from large-magnitude, Pleistocene-to-Holocene silicic eruptions of caldera volcanoes along the Central American Volcanic Arc (CAVA) were found throughout drill cores collected from Lake Petén Itzá. These ash beds were used to establish a robust chronology extending back 400 ka. We used major- and trace-element glass composition to establish 12 well-constrained correlations between the lacustrine tephra layers in Lake Petén Itzá sediments and dated deposits at the CAVA source volcanoes, and with their marine equivalents in eastern Pacific Ocean sediments. The data also enabled revision of eight previous determinations of erupted volumes and masses, and initial estimates for another four eruptions, as well as the designation of source areas for 14 previously unknown eruptions. The new and revised sedimentation rates for the older sediment successions identify the interglacial of MIS5a between 84 and 72 ka, followed by a stadial between 72 and 59 ka that corresponds to MIS4. We modified the age models for the Lake Petén Itzá sediment sequences, extended the paleoclimate and paleoecological record for this Neotropical region to ∼400 ka, and determined the magnitude and timing of CAVA eruptions.
    Type: Article , PeerReviewed
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    DOI: 10.1016/j.quascirev.2016.08.023
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  • 10
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    Late Cenozoic tephrostratigraphy offshore the southern Central American Volcanic Arc: 1. Tephra ages and provenance (2016)
    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 17 (11). pp. 4641-4668.
    Details
    Publication Date: 2019-02-01
    Description: We studied the tephra inventory of 18 deep sea drill sites from six DSDP/ODP legs (Legs 84, 138, 170, 202, 205, 206) and two IODP legs (Legs 334 and 344) offshore the southern Central American Volcanic Arc (CAVA). Eight drill sites are located on the incoming Cocos plate and ten drill sites on the continental slope of the Caribbean plate. In total we examined ∼840 ash-bearing horizons and identified ∼650 of these as primary ash beds of which 430 originated from the CAVA. Correlations of ash beds were established between marine cores and with terrestrial tephra deposits, using major and trace element glass compositions with respect to relative stratigraphic order. As a prerequisite for marine-terrestrial correlations we present a new geochemical data set for significant Neogene and Quaternary Costa Rican tephras. Moreover, new Ar/Ar ages for marine tephras have been determined and marine ash beds are also dated using the pelagic sedimentation rates. The resulting correlations and provenance analyses build a tephrochronostratigraphic framework for Costa Rica and Nicaragua that covers the last 〉8 Myr. We define 39 correlations of marine ash beds to specific tephra formations in Costa Rica and Nicaragua; from the 4.15 Ma Lower Sandillal Ignimbrite to the 3.5 ka Rincón de la Vieja Tephra from Costa Rica, as well as another 32 widely distributed tephra layers for which their specific region of origin along Costa Rica and Nicaragua can be constrained.
    Type: Article , PeerReviewed
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    DOI: 10.1002/2016GC006503
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