| 1. |
- Preusser, Frank, et al.
(author)
-
Direct dating of Quaternary phreatic maar eruptions by luminescence methods
- 2011
-
In: Geology. - 0091-7613 .- 1943-2682. ; 39:12, s. 1135-1138
-
Journal article (peer-reviewed)abstract
- The suitability of quartz optically stimulated luminescence (OSL) and feldspar infrared stimulated luminescence (IRSL) for the direct dating of phreatic eruptions was tested on examples from the Eifel Volcanic Field, Germany. The mean IRSL age of 11.6 +/- 0.5 ka for Ulmener Maar Tephra is in excellent agreement with the independent age control (11 +/- 0.1 ka), but the mean OSL age of 14.2 +/- 0.6 ka overestimates the known age by 3 ka. For Meerfelder Maar Tephra, consistent IRSL (mean 74.9 +/- 5.0 ka) and OSL ages (74.9 +/- 5.5 ka) have been observed. The consistent results from Meerfelder Maar imply that the overestimation observed for Ulmener Maar quartz OSL might not be relative to the eruption age, but rather represents a small absolute offset. In samples taken from deposits of the eruption of Laacher See Volcano, no resetting of the OSL signal and highly scattered IRSL estimates were found. This implies that phreatomagmatic eruptions are less well suited for this dating approach compared to pure phreatic maar eruptions, where the effect of high-pressure shock waves probably dominates the process of resetting the luminescence signal.
|
|
| 2. |
- Rufer, Daniel, et al.
(author)
-
Late Quaternary history of the Vakinankaratra volcanic field (central Madagascar) : insights from luminescence dating of phreatomagmatic eruption deposits
- 2014
-
In: Bulletin of Volcanology. - : Springer Science and Business Media LLC. - 0258-8900 .- 1432-0819. ; 76:5, s. 817-
-
Journal article (peer-reviewed)abstract
- The Quaternary Vakinankaratra volcanic field in the central Madagascar highlands consists of scoria cones, lava flows, tuff rings, and maars. These volcanic landforms are the result of processes triggered by intracontinental rifting and overlie Precambrian basement orNeogene volcanic rocks. Infrared-stimulated luminescence (IRSL) dating was applied to 13 samples taken from phreatomagmatic eruption deposits in the Antsirabe-Betafo region with the aim of constraining the chronology of the volcanic activity. Establishing such a chronology is important for evaluating volcanic hazards in this densely populated area. Stratigraphic correlations of eruption deposits and IRSL ages suggest at least five phreatomagmatic eruption events in Late Pleistocene times. In the Lake Andraikiba region, two such eruption layers can be clearly distinguished. The older one yields ages between 109 +/- 15 and 90 +/- 11 ka and is possibly related to an eruption at the Amboniloha volcanic complex to the north. The younger one gives ages between 58 +/- 4 and 47 +/- 7 ka and is clearly related to the phreatomagmatic eruption that formed Lake Andraikiba. IRSL ages of a similar eruption deposit directly overlying basement laterite in the vicinity of the Fizinana and Ampasamihaiky volcanic complexes yield coherent ages of 68 +/- 7 and 65 +/- 8 ka. These ages provide the upper age limit for the subsequently developed Iavoko, Antsifotra, and Fizinana scoria cones and their associated lava flows. Two phreatomagmatic deposits, identified near Lake Tritrivakely, yield the youngest IRSL ages in the region, with respective ages of 32 +/- 3 and 19 +/- 2 ka. The reported K-feldspar IRSL ages are the first recorded numerical ages of phreatomagmatic eruption deposits in Madagascar, and our results confirm the huge potential of this dating approach for reconstructing the volcanic activity of Late Pleistocene to Holocene volcanic provinces.
|
|
| 3. |
- Rufer, Daniel, et al.
(author)
-
Proposing new approaches for dating young volcanic eruptions by luminescence methods
- 2012
-
In: Geochronometria. - : Walter de Gruyter GmbH. - 1733-8387 .- 1897-1695. ; 39:1, s. 48-56
-
Journal article (peer-reviewed)abstract
- The application of luminescence dating to young volcanic sediments has been first investigated over three decades ago, but it was only with the technical innovations of the last decade that such analyses became viable. While current analytical procedures show promise for dating late Quaternary volcanic events, most efforts have been aimed at unconsolidated volcanic tephra. Investigations into direct dating of lava flows or of non-heated volcanoclastics like phreatic explosion layers, however, remain scarce. These volcanic deposits are of common occurrence and represent important chrono- and volcanostratigraphic markers. Their age determination is therefore of great importance in volcanologic, tectonic, geomorphological and climate studies. In this article, we propose the use of phreatic explosion deposits and xenolithic inclusions in lava flows as target materials for luminescence dating applications. The main focus is on the crucial criterion whether it is probable that such materials experience complete luminescence signal resetting during the volcanic event to be dated. This is argued based on the findings from existing literature, model calculations and laboratory tests.
|
|
| 4. |
|
|
| 5. |
- Schreurs, Guido, et al.
(author)
-
Benchmarking analogue models of brittle thrust wedges
- 2016
-
In: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 92, s. 116-139
-
Journal article (peer-reviewed)abstract
- We performed a quantitative comparison of brittle thrust wedge experiments to evaluate the variability among analogue models and to appraise the reproducibility and limits of model interpretation. Fifteen analogue modeling laboratories participated in this benchmark initiative. Each laboratory received a shipment of the same type of quartz and corundum sand and all laboratories adhered to a stringent model building protocol and used the same type of foil to cover base and sidewalls of the sandbox. Sieve structure, sifting height, filling rate, and details on off-scraping of excess sand followed prescribed procedures. Our analogue benchmark shows that even for simple plane-strain experiments with prescribed stringent model construction techniques, quantitative model results show variability, most notably for surface slope, thrust spacing and number of forward and backthrusts. One of the sources of the variability in model results is related to slight variations in how sand is deposited in the sandbox. Small changes in sifting height, sifting rate, and scraping will result in slightly heterogeneous material bulk densities, which will affect the mechanical properties of the sand, and will result in lateral and vertical differences in peak and boundary friction angles, as well as cohesion values once the model is constructed. Initial variations in basal friction are inferred to play the most important role in causing model variability. Our comparison shows that the human factor plays a decisive role, and even when one modeler repeats the same experiment, quantitative model results still show variability. Our observations highlight the limits of up-scaling quantitative analogue model results to nature or for making comparisons with numerical models. The frictional behavior of sand is highly sensitive to small variations in material state or experimental set-up, and hence, it will remain difficult to scale quantitative results such as number of thrusts, thrust spacing, and pop-up width from model to nature.
|
|
