Helmut Brückner

Effects of Feldspar Contamination on Equivalent dose and the Shape of Growth Curve for OSL of Silt-Sized Quartz Extracted from Chinese Loess

Effects of Feldspar Contamination on Equivalent dose and the Shape of Growth Curve for OSL of Silt-Sized Quartz Extracted from Chinese Loess This study examines the effects of feldspar contamination of different extent (by fluorosilicic acid etching for different time periods and mixing pure quartz with different percentage of unetched grains) on blue-light stimulated luminescence (BLSL) of quartz (38-63 μm) for Chinese loess. In particular, the De values and the shape of growth curves will be examined. The results show that: (1) The De determined using feldspar in Chinese loess is obviously underestimated, and infra-red stimulated luminescence (IRSL) has a greater underestimation than BLSL. For aliquots with no fluorosilicic acid etching, an IRSL De underestimation of ∼30% is observed for a sample with an expected age of ∼22 ka, ∼19% underestimation for BLSL, and ∼10% for post-IR BLSL. For quartz BLSL, the contamination of feldspar, which has not dissolved by fluorosilicic acid etching, will inevitably lead to age underestimation. We suggest that the IR-checking should be performed for every single aliquot. An aliquot should be excluded from the final De calculation if obvious IRSL signal was observed. (2) For the sample under examination blue LED stimulation can reset both IRSL and BLSL signals of feldspars, while IR stimulation cannot reset the BLSL of feldspars. (3) For multiple-mineral aliquot the growth curve shape of the post-IR BLSL is different from that of the IRSL, and within 25 Gy it is identical to that of the pure quartz BLSL. The contamination of feldspars in quartz will change the shape of a growth curve for quartz BLSL.

Late Quaternary Shorelines in India

Littoral lowlands in India were examined to find indicators for higher sea levels, date the sediments (with the 14C, 230Th/234U and Electron Spin Resonance dating techniques) and reconstruct the geomorphologic and tectonic evolution during the late Quaternary. — On Kathiawar Peninsula the miliolite problem (marine versus eolian genesis) could be solved. The inland occurrences of these organogenic grainstones are of eolian origin. In the coastal belt miliolites up to +4 m above mean sea level were deposited by the sea during the last interglacial transgression. This is confirmed by the dating of other marine accumulation terraces up to this altitude which are also of stage 5e of the oxygenisotope record (c. 125 ka). The Holocene transgression reached its maximum around 5,000–6,000 BP when sea level was c. 1 m higher (14C-dated marshy soils and marine sands). The Konkan Coast between Bombay and Goa is a ria-type coast. So far no Pleistocene marine deposits have been detected. Cross-sections of the lower river courses and creeks also indicate subsidence. Here, the Holocene transgression reached its maximum c. 2,000–2,800 BP, was at most 1 m higher and deposited beach ridges. On the Tamilnadu side of southern India, between Cape Comorin and Rameswaram, the 125 ka-strandline is found occurring not higher than 4 m above present sea level, which indicates subsidence or stability of the coast rather than emergence. The Holocene transgression reached up to +1 m. The Kerala side is devoid of Pleistocene marine deposits above present sea level, and even the Holocene ones are drowned. — It is worth noting that in Peninsular India Pleistocene marine deposits older than stage 5 are missing. It seems that for geologically old continents other sea level fluctuation curves than those generally published for the Quaternary are valid.

Beachrock-type calcarenitic tsunamites along the shores of the eastern Ionian Sea (western Greece) – case studies from Akarnania, the Ionian Islands and the western Peloponnese

Th is paper presents geo-scientifi c evidence of beachrock-type calcarenitic tsunamites from three study areas in western Greece, namely from the Bays of Aghios Nikolaos (Akarnania), Langadakia (Cefalonia Island) and Aghios Andreas (Peloponnese). Geomorphological, sedimentological, micromorphological and geochemical studies were conducted to clarify depositional processes and the post-sedimentary evolution. Calcarenitic and locally conglomeratic carbonate crusts were studied in natural outcrops along the seafront and in vibracores. High-resolution topographic surveys and 3D-visualisation were carried out by diff erential GPS and LIDAR measurements. Tsunami impact was dated by a combined approach of radiocarbon, OSL and archaeological age determination and compared to local tsunami and earthquake chronologies. We found sedimentary structures such as basal unconformities, rip-up and intra-clasts, evidence of fi ning upward, thinning landward and upward increase in sorting as well as bi-to multimodal deposits and injection structures all of which are described as features typical of recent or historic tsunami deposits. Typically non-littoral sedimentary features such as load casts and convolute bedding further indicate gravity driven processes in water-saturated sheets of allochthonous deposits and are well known from, for example, turbidites. Moreover, thin section analyses revealed highenergy shockand impact-borne cracking and shearing eff ects. Our results show that cementation of tsunami deposits may occur by post-depositional pedogenetic decalcifi cation of higher sections and subsequent secondary carbonate precipitation in lower sections of tsunami deposits provided that they were deposited above sea level. Th e calcarenitic tsunamites encountered in the three study areas match the defi nition of beachrock sensu stricto. Th is is thus the fi rst paper giving examples of beachrock sequences that are interpreted as partially cemented tsunami deposits. Consequently, beachrock is recommended not to be used as sea level indicator in future studies unless a tsunamigenic formation can be defi nitely excluded. Dating results brought to light young, mostly Holocene ages of tsunami sediments. In the Bay of Aghios Andreas, western Peloponnese, we found spectacular traces that Olympia’s ancient harbour site Pheia was destroyed by tsunami impact in the 6th cent. AD and covered by a rapidly cemented, up to 3 m-thick beachrock-type tsunami deposit.

Delta Evolution and Culture — Aspects of Geoarchaeological Research in Miletos and Priene

During the last 5500 or so years, the Latmian Gulf has been silted up by the progradation of the Buyuk Menderes (Maiandros) delta. Thus, the ancient sea port cities Miletos and Priene became landlocked. Based on the interpretation of drill cores this paper presents evidence that the area of Miletos consisted of islands when the first settlers arrived ca. 3500-3000 b.c. During the Roman era, strong siltation processes can be proven. When Priene was founded anew around 350 b.c., the eastern embayment at the foot of its promontory had already turned into a lake, whereas the western embayment was more suitable for a harbour site.

Holocene palaeogeographies of the central Acheloos River delta (NW Greece) in the vicinity of the ancient seaport Oiniadai

The shipsheds of the ancient seaport Oiniadai (5th-3rd cent. BC), today located in the central Acheloos River delta on top of the Trikardo hills 9 km inland, document considerable coastal changes. This paper deals with the reconstruction of coastal palaeogeographies in that area since the mid-Holocene. Sediments encountered in 51 vibracores were used to detect the distribution pattern of facies. Facies discrimination was based on sedimentological and micro- and macrofaunal analyses. Palaeobotanical, micromorphological and geophysical studies were accomplished to rebuild palaeoenvironmental settings. A geochronology was set up by means of 50 14C-AMS-dates which also helped to establish a relative sea level curve. At 6000 cal BC, delta progradation started from the north and, by 4500 cal BC, closed off a large lagoon north of Trikardo. At 5400-3100 cal BC, a southern delta arm approached and, by 1350-1000 cal BC, surrounded Trikardo by two distributaries. At 600-200 cal BC, a river channel flowed into the Lagoon of Oiniadai. Thereafter, at 200 cal BC, the delta front switched to the southeast. Delta progradation in todays direction started during Byzantine times. Essential geoarchaeological results are that (i) an Early Helladic harbour, unknown until now, existed southeast of Trikardo on a lagoonal shore and that (ii) Oiniadais shipsheds were, in Classical Hellenistic times, accessible from the sea via a lagoon.

Holocene sea levels along the Andaman Sea coast of Thailand

For the Malay-Thai Peninsula several sea-level curves for the younger Holocene, based on field evidence as well as on hydro-isostatic modelling of a far-field site, have been published. The general assumption is a rapid rise to a mid-Holocene maximum up to +5 m above present sea level, followed by a constant or oscillating regression. However, from the Andaman Sea coast of Thailand, which was affected by the 2004 tsunami, only isolated observations are available regarding Holocene sea levels. Thus, the timing and magnitude of the Holocene highstand as well as the course of the regression remain to be defined. As several palaeotsunamis could be detected in the meantime it is important to know the related sea levels as exactly as possible to judge the energy, inundation width and potential wave height of these events. Therefore, fixed biological indicators from the rocky coasts of the Phang-nga Bay and Phuket, as well as morphological indicators from beach-ridge and swale sequences along the exposed west coast (Ko Phra Thong) were studied, to gain information about the Holocene sea-level development in this region. While oyster and coral data from the Phang-nga Bay and Phuket document a Holocene maximum of +2.6 m at 5700 cal. BP, the ridge crests and swale bases in the northwest of the study area point to maximum heights of +1.5–2.0 m above the present level around 5300 years ago. During the last 3000 years, to when the largest part of the Holocene palaeotsunami deposits from Thailand was dated, relative sea levels (RSL) in both areas did not exceed +1.5 m.

Problems encountered with absolute dating (U-series, ESR) of Spanish calcretes

Abstract U-series and ESR dating techniques were applied to calcretes sampled at locations with a chronostratigraphic framework in Spain. ESR dating considering the organic signal at g = 2.0045 leads to an age overestimation up to 200 ka. The percentage of error decreases, however, with increasing age, so that this method may be more suitable to the dating of early Pleistocene samples. Despite the unique limitations of the ESR method to the dating of calcretes, only a differentiation of early, middle, and late Pleistocene calcretes is reasonable.

The Gyra washover fan in the Lefkada Lagoon, NW Greece—possible evidence of the 365 AD Crete earthquake and tsunami

Coastal geomorphological and geological archives store valuable information about the geodynamic evolution of coastal areas and the contributing geomorphodynamic processes. The coastal geomorphology of the Lefkada– Preveza coastal zone, NW Greece, holds evidence for the influence of both gradual, low-energy and episodic, high-energy coastal processes. Situated close to the Hellenic Arc and the Cefalonia transform fault, the area belongs to one of the seismically most active regions in the Mediterranean. Thus, tsunami events are assumed to have contributed to the coastal evolution in the study area according to tsunami catalogues and field evidence from previous investigations. The northern part of the Lefkada Lagoon, separated from the Ionian Sea by an extensive barrier beach system, is characterized by a number of fan-like washover structures, formed by different washover generations. In this paper, we present detailed geomorphological, sedimentological, geochemical and foraminiferal investigations on the most prominent fan structure, the Gyra fan, based on terrestrial and lagoonal sediment cores. The Gyra fan consists of a coarse-grained sequence of fully marine origin on top of lagoonal mud and a palaeosol, respectively. The sequence shows numerous characteristics of extreme wave deposits. Due to the dimension and morphology of the fan, the existence of up to four consistent and correlative stratigraphic subunits, their landward thinning and their comparable sedimentary characteristics, we argue that a tsunami event induced the formation of the Gyra fan, comprising at least four major inundation impulses. According to radiocarbon dates, this geomorphological structure was most likely formed by teletsunami effects triggered by the 365 AD earthquake off western Crete.

A comparison of different TL-techniques on loess samples from rheindahlen (F.R.G.)

Abstract 9 TL samples of the loess profile Rheindahlen (Lower Rhine Area, Germany), covering the time span of the last 300 ka, were studied. Systematic investigation was carried out using different filters and preheating procedures. ED determinations were done by the additive dose and the regeneration method. The annual dose was determined by AAS, alpha counting, NAA and gamma spectrometry in the laboratory and in the field. The results show that the Weichselian loess is datable whereas no TL age differentiation between loesses of Stage 6 and Stage 8 is possible. If the accumulated dose (ED) is in the ‘600 Gy region’, every apparent TL age between 100 and 300 ka can be obtained. This leads to the conclusion that in Rheindahlen no reliable TL ages are available for loess deposits underneath the Eemian soil (Stage 5e).

Sediment Transport and Hydrodynamic Parameters of Tsunami Waves Recorded in Onshore Geoarchives

ABSTRACT Brill, D.; Pint, A.; Jankaew, K.; Frenzel, P.; Schwarzer, K.; Vött, A., and Brückner, H., 2014. Sediment transport and hydrodynamic parameters of tsunami waves recorded in onshore geoarchives. In regions with a short historical tsunami record, the assessment of long-term tsunami risk strongly depends on geological evidence of prehistoric events. Whereas dating tsunami deposits is already well established, magnitude assessment based on remaining sedimentary structures is still a major challenge. In this study, two approaches were applied to deduce transport processes and hydrodynamic parameters of tsunami events from onshore deposits found in the coastal plain of Ban Bang Sak, SW Thailand: (1) The maximum offshore sediment source was determined using granulometry, geochemistry, mineralogy and foraminifera of the tsunamites, and reference samples from various marine and terrestrial environments, and (2) the onshore flow velocities and flow depths of associated tsunami waves were estimated by means of sedimentation modelling. In the case of the Indian Ocean tsunami (IOT) of 2004, modelled flow velocities of 3.7 to 4.9 m/s, modelled onshore flow depths of up to 5.5 m, and a sediment source from offshore areas shallower than a 45-m water depth—including littoral sediments transported as bedload and suspended load from the shallow subtidal zone—are in agreement with quotations based on survivor videos and posttsunami surveys. For a 500- to 700-year-old predecessor, comparable flow velocities and flow depths of 4.1 to 5.9 m/s and 4.0 to 7.5 m, respectively, were modelled, indicating a similar magnitude as the IOT 2004. Comparable values of maximum transport distance and depth of wave erosion were also found. In the case of three older tsunami candidates, dated to 1180 to 2000 cal BP, the deposits indicate partly similar source areas with water depths of less than 45 m and partly shallower source areas restricted solely to the beach. Whereas the former tsunamis are interpreted as events similar to 2004, the latter are more likely storms or tsunamis of a lower magnitude.