Manuel Dominguez-Rodrigo, Enrique Baquedano, Abel Moclan
et al.
The role of megafaunal exploitation in early human evolution remains debated. Occasional use of large carcasses by early hominins has been considered by some as opportunistic, possibly a fallback dietary strategy, and for others a more important survival strategy. At Olduvai Gorge, evidence for megafaunal butchery is scarce in the Oldowan of Bed I but becomes more frequent and widespread after 1.8 Ma in Bed II, coinciding with the emergence of Acheulean technologies, but not functionally related to the main Acheulian tool types. Here, we present the earliest direct evidence of proboscidean butchery, including a newly documented elephant butchery site (EAK). This shift in behavior is accompanied by larger, more complex occupation sites, signaling a profound ecological and technological transformation. Rather than opportunistic scavenging, these findings suggest a strategic adaptation to megafaunal resources, with implications for early human subsistence and social organization. The ability to systematically exploit large prey represents a unique evolutionary trajectory, with no direct modern analogue, since modern foragers do so only episodically.
Guillermo Rodríguez-Gómez, M. Patrocinio Espigares, Bienvenido Martínez-Navarro
et al.
The Early Pleistocene sites of Orce in southeastern Spain, including Fuente Nueva-3 (FN3), Barranco León (BL) and Venta Micena (VM), provide important insights into the earliest hominin populations and Late Villafranchian large mammal communities. Dated to approximately 1.4 million years ago, FN3 and BL preserve abundant Oldowan tools, cut marks and a human primary tooth, indicating hominin activity. VM, approximately 1.6 million years old, is an outstanding site because it preserves an exceptionally rich assemblage of large mammals and predates the presence of hominins, providing a context for pre-human conditions in the region. Research suggests that both hominins and giant hyenas were essential to the accumulation of skeletal remains at FN3 and BL, with secondary access to meat resources exploited by saber-toothed felids. This aim of this study aims to correlate the relative abundance of large herbivores at these sites with their estimates of Carrying Capacity (CC) and Total Available Biomass (TAB) using the PSEco model, which incorporates survival and mortality profiles to estimate these parameters in paleoecosystems. Our results show: (i) similarities between quarries VM3 and VM4 and (ii) similarities of these quarries with BL-D (level D), suggesting a similar formation process; (iii) that the role of humans would be secondary in BL-D and FN3-LAL (Lower Archaeological Level), although with a greater human influence in FN3-LAL due to the greater presence of horses and small species; and (iv) that FN3-UAL (Upper Archaeological Level) shows similarities with the expected CC values for FN3/BL, consistent with a natural trap of quicksand scenario, where the large mammal species were trapped according to their abundance and body mass, as there is a greater presence of rhinos and mammoths due to the greater weight per unit area exerted by their legs. Given the usefulness of this approach, we propose to apply it first to sites that have been proposed to function as natural traps.
Abstract The Clydach Valley Subgroup (Courceyan) records a dip section through an Early Carboniferous shallow marine, carbonate shelf and consists of three oolitic formations separated by paludal/peritidal units with abundant evidence of subaerial exposure in proximal areas. The lower part correlates with the Kinderhookian–Osagean Boundary Excursion, with allochem data indicating a minimum δ13C value for marine carbonate of +4.5‰, with associated δ18O of −4.6‰. Marine carbonate δ13C and δ18O values of +2‰ and −2‰, respectively, were estimated for the younger part. Allochem isotopic data yield a well‐defined mixing line consistent with stabilisation in meteoric water at varied water: rock ratios, the degree of stabilisation increasing up‐dip and up‐stratigraphy. Two distinct diagenetic styles closely correlate with evidence for the presence (Diagenetic Regime 1) or absence (Diagenetic Regime 2) of subaerial exposure, non‐ferroan and ferroan calcite cement dominating respectively. Five cement zones (Zones 2–6) defined by iron content occur in Diagenetic Regime 1, irrespective of formation, indicating a similar sequence of palaeohydrological changes affected repeated depositional cycles. Zones 3–5 are considered meteoric based on their isotopic composition (δ18O: −5.8 to −11.1‰ and δ13C: −3.7 to −6.2‰) and form distinct clusters dependent on zone, age and location. Pedogenic carbonates and meteoric cements record a long term increase in meteoric δ18O values: −7.8‰ during the Kinderhookian–Osagean Boundary Excursion, −6.9‰ during diagenesis of the upper part of the subgroup and −6.3‰ associated with initial deposition of the overlying Llanelly Formation. This is consistent with global sea water trends, but an element of climate change cannot be ruled out. Increases in cement δ18O values as meteoric systems become established (Zone 3–4) indicate repeated short term variation in rainwater composition probably driven by climate change, but also suggests a link between climate and the depositional cycle.
Paleo-oxbow lake sediments can provide archives to reconstruct paleo-channel evolution and flooding history of the river. Multi-proxy approaches including detailed sediment stratigraphy, sedimentology and geochemistry have been implemented in a high-resolution sedimentary section of paleo-oxbow lake of the Yellow River within the Zoige Basin on the NE Tibetan Plateau, to reconstruct regional environmental changes and extreme overbank flooding history. Our results suggest that not only traditional sedimentological proxies, but also chemical elements can be applied in defining sequences with different genetic types, especially the paleoflood deposits in the paleo-oxbow profile. Two units of late-Holocence extreme overbank flooding deposits (OFDs) are identified in terms of the significantly higher proportions of sand, high contents of SiO2, Na2O, Ba, low contents of Al2O3, Fe2O3, MgO, K2O, Ti, Rb and high values of Zr/Fe, Zr/Rb ratios. These extraordinary flood events within the Zoige Basin were dated back to 2,960 ± 240–2,870 ± 270 a and 1840 ± 200–1700 ± 160 a, in response to the mid-Holocene climatic optimum to the late Holocene and the Dark Age Cold Period (DACP). And the strong rainfall caused by the abnormal atmospheric circulation during the period of climate transition and abrupt change may led to the frequent occurrence of extreme flood events in the source region of the Yellow River. These findings are important for understanding the response of regional fluvial system to high climatic instability and provide a new perspective for us to analyze the risk of flood disasters on the Tibetan Plateau under the background of climate change.
Lucas M. Fennell, Federico Exequiel Martos, Nicolás A. Peluffo
et al.
The Aconcagua region constitutes a classical site to study the growth of the Andes, being host of the highest mountain of South America and focus of numerous investigations since its first description by Charles Darwin almost 200 years ago. The last detailed works in this area characterized it as a typical thin-skinned fold-thrust belt with a basal detachment located in the lower evaporitic units of the Mesozoic sequences. Previous authors in this area correlated the different thrust sheets on the basis of their marine fossils, sedimentological characteristics and structural relations. Although these criteria were useful for the identification of the marine and evaporitic units, the resemblance between the nonmarine red beds and among the different volcanic units has difficulted their unequivocal assignment. Moreover, the inaccessibility of the outcrops and the lack of an adequate geochronological control has led to underestimate the importance of the Aconcagua fold-thrust belt in the last couple of years, being characterized as a secondary feature in Andean orogenesis. A series of new field observations, sedimentological studies and geochronological analyses were performed to update the geological map of this area and build a schematic cross section along the Río Cuevas at 32°50’S in west-central Argentina. These studies allowed the identification of important variations on the thickness of the Upper Jurassic nonmarine sequences associated with the activity of normal faults and the development of structural highs. Many of these normal faults are presently inverted, which suggests that tectonic inversion played an important role in the structuration of this region, leading to a deformational style that varies from a thick-skinned inner domain towards a thin-skinned frontal sector. A series of sedimentological profiles aided by four new U-Pb detrital zircon analyses and its integration with new geochronological databases allowed the documentation of previously unrecognized Paleogene deposits, the age reassignation of several volcanic and sedimentary units and the modification of the stratigraphy. Finally, at least three contractional events with different structural mechanisms were identified along this transect, revealing a dynamic tectonic evolution that underscores the role of structural inheritance and the relevance of the Aconcagua fold-thrust belt in the Andean orogeny.
Abstract Macrofossils with unambiguous biogenic origin and predating the one-billion-year-old multicellular fossils Bangiomorpha and Proterocladus interpreted as crown-group eukaryotes are quite rare. Horodyskia is one of these few macrofossils, and it extends from the early Mesoproterozoic Era to the terminal Ediacaran Period. The biological interpretation of this enigmatic fossil, however, has been a matter of controversy since its discovery in 1982, largely because there was no evidence for the preservation of organic walls. Here we report new carbonaceous compressions of Horodyskia from the Tonian successions (~950–720 Ma) in North China. The macrofossils herein with bona fide organic walls reinforce the biogenicity of Horodyskia. Aided by the new material, we reconstruct Horodyskia as a colonial organism composed of a chain of organic-walled vesicles that likely represent multinucleated (coenocytic) cells of early eukaryotes. Two species of Horodyskia are differentiated on the basis of vesicle sizes, and their co-existence in the Tonian assemblage provides a link between the Mesoproterozoic (H. moniliformis) and the Ediacaran (H. minor) species. Our study thus provides evidence that eukaryotes have acquired macroscopic size through the combination of coenocytism and colonial multicellularity at least ~1.48 Ga, and highlights an exceptionally long range and morphological stasis of this Proterozoic macrofossils.
James Hill, Stuart Black, Alejandro Araujo-Murakami
et al.
Phytolith analysis is a well-established archaeobotanical tool, having provided important insights into pre-Columbian crop cultivation and domestication across Amazonia through the Holocene. Yet, its use as a palaeoecological tool is in its infancy in Amazonia and its effectiveness for reconstructing pre-Columbian land-use beyond archaeological sites (i.e., ‘off-site’) has so far received little critical attention. This paper examines both new and previously published soil phytolith data from SW Amazonia to assess the robustness of this proxy for reconstructing pre-Columbian land-use. We conducted the study via off-site soil pits radiating 7.5 km beyond a geoglyph in Acre state, Brazil, and 50 km beyond a ring-ditch in northern Bolivia, spanning the expected gradients in historical land-use intensity. We found that the spatio-temporal patterns in palm phytolith data across our soil-pit transects support the hypothesis that pre-Columbian peoples enriched their forests with palms over several millennia, although phytoliths are limited in their ability to capture small-scale crop cultivation and deforestation. Despite these drawbacks, we conclude that off-site soil phytolith analysis can provide novel insights into pre-Columbian land use, provided it is effectively integrated with other land-use (e.g., charcoal) and archaeological data.
<p>We present a high-resolution airborne radar data set (EGRIP-NOR-2018) for the onset region of the Northeast Greenland Ice Stream (NEGIS). The radar data were acquired in May 2018 with the Alfred Wegener Institute's multichannel ultra-wideband (UWB) radar mounted on the Polar 6 aircraft. Radar profiles cover an area of <span class="inline-formula">∼24</span> 000 km<span class="inline-formula"><sup>2</sup></span> and extend over the well-defined shear margins of the NEGIS. The survey area is centered at the location of the drill site of the East Greenland Ice-Core Project (EastGRIP), and several radar lines intersect at this location. The survey layout was designed to (i) map the stratigraphic signature of the shear margins with radar profiles aligned perpendicular to ice flow, (ii) trace the radar stratigraphy along several flow lines, and (iii) provide spatial coverage of ice thickness and basal properties. While we are able to resolve radar reflections in the deep stratigraphy, we cannot fully resolve the steeply inclined reflections at the tightly folded shear margins in the lower part of the ice column. The NEGIS is causing the most significant discrepancies between numerically modeled and observed ice surface velocities. Given the high likelihood of future climate and ocean warming, this extensive data set of new high-resolution radar data in combination with the EastGRIP ice core will be a key contribution to understand the past and future dynamics of the NEGIS. The EGRIP-NOR-2018 radar data products can be obtained from the PANGAEA data publisher (<span class="uri">https://doi.pangaea.de/10.1594/PANGAEA.928569</span>; <span class="cit" id="xref_altparen.1"><a href="#bib1.bibx21">Franke et al.</a>, <a href="#bib1.bibx21">2021</a><a href="#bib1.bibx21">a</a></span>).</p>
Successful peatland restoration requires a knowledge of peatland stratigraphy in order to understand the hydrological and ecological conditions under which peat formation occurred and to identify realistic objectives and measures for the specific site. So far, the ability to accurately identify peat deposits and lake sediments has been largely restricted to experts. To facilitate identification by others, we provide an identification key for common peatland deposits in Germany and introduce standardised portraits of 17 peat and six gyttja types with extensive descriptions and supporting photographs. We also provide information on the indicative value of the peatland deposits in terms of site conditions at the time of deposition.
We assessed sediment coring, data acquisition, and publications from
the North Pacific (north of 30° N) from 1951 to 2016. There
are 2134 sediment cores collected by American, French, Japanese,
Russian, and international research vessels across the North Pacific
(including the Pacific subarctic gyre, Alaskan gyre, Japan margin,
and California margin; 1391 cores), the Sea of Okhotsk (271 cores),
the Bering Sea (123 cores), and the Sea of Japan (349 cores) reported
here. All existing metadata associated with these sediment cores are
documented here, including coring date, location, core number,
cruise number, water depth, vessel metadata, and coring technology.
North Pacific sediment core age models are built with isotope
stratigraphy, radiocarbon dating, magnetostratigraphy,
biostratigraphy, tephrochronology, % opal, color, and
lithological proxies. Here, we evaluate the iterative generation of
each published age model and provide comprehensive documentation of
the dating techniques used, along with sedimentation rates and age
ranges. We categorized cores according to the availability of
a variety of proxy evidence, including biological (e.g., benthic and
planktonic foraminifera assemblages), geochemical (e.g., major trace
element concentrations), isotopic (e.g., bulk sediment nitrogen,
oxygen, and carbon isotopes), and stratigraphic (e.g., preserved
laminations) proxies. This database is a unique resource to the
paleoceanographic and paleoclimate communities and provides
cohesive accessibility to sedimentary sequences, age model
development, and proxies. The data set is publicly available through
PANGAEA at <a href="https://doi.org/10.1594/PANGAEA.875998" target="_blank">https://doi.org/10.1594/PANGAEA.875998</a>.
We present obspyDMT, a free, open-source software toolbox for the
query, retrieval, processing and management of seismological data sets,
including very large, heterogeneous and/or dynamically growing ones. ObspyDMT
simplifies and speeds up user interaction with data centers, in more
versatile ways than existing tools. The user is shielded from the
complexities of interacting with different data centers and data exchange
protocols and is provided with powerful diagnostic and plotting tools to
check the retrieved data and metadata. While primarily a productivity tool
for research seismologists and observatories, easy-to-use syntax and plotting
functionality also make obspyDMT an effective teaching aid. Written in the
Python programming language, it can be used as a stand-alone command-line
tool (requiring no knowledge of Python) or can be integrated as a module with
other Python codes. It facilitates data archiving, preprocessing, instrument
correction and quality control – routine but nontrivial tasks that can
consume much user time. We describe obspyDMT's functionality, design and
technical implementation, accompanied by an overview of its use cases. As an
example of a typical problem encountered in seismogram preprocessing, we show
how to check for inconsistencies in response files of two example stations.
We also demonstrate the fully automated request, remote computation and
retrieval of synthetic seismograms from the Synthetics
Engine (Syngine) web service of the Data Management Center (DMC) at the Incorporated Research
Institutions for Seismology (IRIS).
Instrumenti, ki zvezno merijo nivo, temperaturo in prevodnost vode so bili postavljeni na 10 točkah. Opazovalna mesta so postavljena na dnu, kjer jama doseže vode Reke (Timave), ki zbira podzemne vode klasičnega Krasa. Predhodne analize velikega števila podatkov, ki smo jih zbrali do sedaj, pomagajo bolje določiti način pretakanja vode v globinah. Ugotovili smo tri različne vodne valove, vpliv črpanja na nekaterih delih in mešanje različnih voda na drugih.
Some instruments that continuously measure height, temperature and conductivity of waters have been placed in 10 stations. The stations are located on the bottom of the cavities that reach the waters of the Timavo, the underground river that collects the hypogean waters of the Classical Karst. The preliminary analysis of the remarkable amount of data that has been collected up to now helps define the modalities of water circulation in depth better. There are three different types of flood wave, pumping effects in some tracts and mixing of different waters in other tracts.
Abstract
The mapping of the existing ancient terrace of Bengawan Solo (Bengawan means big river) is the preliminary geo-archaeological research conducted in several sites in Bojonegoro region of East Java. The subject found in these ancient terraces were the findings of several Paleolithic tools and vertebrate fossils. Therefore, the aim of the study was to find out the extension of the terrace and to provide a guidance for archaeologists in searching the remains of ancient human culture such as Paleolithic tools and vertebrate fossils. On behalf of the study, firstly the geological mapping was conducted in the studied area and were also to describe the sediment profile and to collect sediment samples (including vertebrate fossils) and also for sedimentary and chemical analysis. In the area studied there were three ancient terraces which were known as, Menden, Jipangulu and Ngandong. Menden terrace (sub-Recent) was exposed at Payaman, Jipangulu terrace (Early Holocene) in Prangi and Wotangare, and Ngandong terrace at Prangi and Kedung village (Solo valley). In the context of stratigraphy, the whole ancient terraces were composed of gravel and coarse sand in the lower part to sandy clay in the upper part. This indicated that the whole terraces were formed by the meandering river of ancient Bengawan Solo. The position of those ancient terraces were relative to the position of recent Bengawan Solo is 2-3 m (Menden terrace), 5-7 m (Jipangulu terrace) and more than 8 m in length (Ngandong terrace). Based on this study, the archaeologists should focus on the gravel to coarse sedimentary strata of the quaternary fluvial system on behalf of searching the cultural artifact of paleolithic including the fossilized remains of human and other quaternary vertebrates within the ancient terrace of Bengawan Solo.
In 2011 four ice cores were extracted from the summit of Alto dell'Ortles
(3859 m), the highest glacier of South Tyrol in the Italian Alps. This
drilling site is located only 37 km southwest from where the Tyrolean
Iceman, ∼ 5.3 kyrs old, was
discovered emerging from the ablating ice field of Tisenjoch (3210 m, near
the Italian–Austrian border) in 1991. The excellent preservation of this
mummy suggested that the Tyrolean Iceman was continuously embedded in
prehistoric ice and that additional ancient ice was likely preserved
elsewhere in South Tyrol. Dating of the ice cores from Alto dell'Ortles based
on <sup>210</sup>Pb, tritium, beta activity and <sup>14</sup>C determinations, combined
with an empirical model (COPRA), provides evidence for a chronologically
ordered ice stratigraphy from the modern glacier surface down to the bottom
ice layers with an age of ∼ 7 kyrs, which confirms the hypothesis. Our
results indicate that the drilling site has continuously been glaciated on frozen
bedrock since ∼ 7 kyrs BP. Absence of older ice on the highest
glacier of South Tyrol is consistent with the removal of basal ice from bedrock
during the Northern Hemisphere Climatic Optimum (6–9 kyrs BP), the warmest
interval in the European Alps during the Holocene. Borehole inclinometric
measurements of the current glacier flow combined with surface ground penetration radar
(GPR) measurements indicate that, due to the sustained atmospheric warming since
the 1980s, an acceleration of the glacier Alto dell'Ortles flow has just
recently begun. Given the stratigraphic–chronological continuity of the
Mt. Ortles cores over millennia, it can be argued that this behaviour has
been unprecedented at this location since the Northern Hemisphere Climatic
Optimum.
Epikras postaja pomembno mesto hidrogeoloških, geomorfoloških in bioloških raziskav. Iz vzorcev pobranih s štirih mest v Škocjanskih jamah, kjer stalno kaplja voda z jamskega stropa, smo identifi cirali meiofavno. Na istih mestih so bili odvzeti tudi vzorci za izolacijo bakterij. Podatke o številu viabilnih celic smo dopolnili z morfološkimi in biokemijskimi lastnostmi izolatov. Izsledki kažejo, da v vzorcih prenikle vode iz epikrasa med bakterijami, ki jih lahko gojimo v in vitro razmerah, prevladujejo po Gramu negativne bakterije.
The epikarst zone becomes an important site for hydrogeological, geomorphological and biological investigations. From the samples at four sites in Škocjanske jame caves where water tricklets constantly drip from the cave ceiling the meiofauna were identifi ed. The sites were screened also for the presence of culturable bacteria. The viable cell counts were supplemented with morphological and biochemical analysis of the isolates. Results show that Gram–negative bacteria prevail among culturable bacteria in the percolating epikarst waters.
Edward H. Bair, Edward H. Bair, Jeff eDozier
et al.
Accurate measurement and modeling of the snowpack energy balance are critical to understanding the terrestrial water cycle. Most of the water resources in the western US come from snowmelt, yet statistical runoff models that rely on the historical record are becoming less reliable because of a changing climate. For physically based snow melt models that do not depend on past conditions, ground based measurements of the energy balance components are imperative for verification. For this purpose, the US Army Corps of Engineers Cold Regions Research and Engineering Laboratory (CRREL) and the University of California, Santa Barbara (UCSB) established the CUES snow study site (CRREL/UCSB Energy Site, http://www.snow.ucsb.edu/) at 2940 m elevation on Mammoth Mountain, California. We describe CUES, provide an overview of research, share our experience with scientific measurements, and encourage future collaborative research. Snow measurements began near the current CUES site for ski area operations in 1969. In the 1970s, researchers began taking scientific measurements. Today, CUES benefits from year round gondola access and a fiber optic internet connection. Data loggers and computers automatically record and store over 100 measurements from more than 50 instruments each minute. CUES is one of only five high altitude mountain sites in the Western US where a full suite of energy balance components are measured. In addition to measuring snow on the ground at multiple locations, extensive radiometric and meteorological measurements are recorded. Some of the more novel measurements include scans by an automated terrestrial LiDAR, passive and active microwave imaging of snow stratigraphy, microscopic imaging of snow grains, snowflake imaging with a multi-angle camera, fluxes from upward and downward looking radiometers, snow water equivalent from different types of snow pillows, snowmelt from lysimeters, and concentration of impurities in the snowpack. We give an example of terrain-corrected snow albedo measurements compared to several models and of sublimation measured from lysimeter and snow pillow melt. We conclude with some thoughts on the future of CUES.
A series of 23 thin, mostly mud-silt turbidites are found interspersed between larger, well-dated and regionally correlated paleoseismic sandy turbidites that extend along most of the Cascadia margin, northwestern United States. Investigation of the structure, distribution, and sedimentology of these thin mud-silt units supports the interpretation of these units as turbidites originating on the continental slope. Interpretation of mud turbidites is inhibited by bioturbation and lower response to analytical and imaging techniques; nevertheless most of the 23 interpreted beds exhibit most of the characteristics of coarser turbidites. These characteristics include sharp bases, fining upward sequences, darker color, increased gamma and CT density and magnetic susceptibility relative to the hemipelagic background, sparse microfossils, high lithic content, and evidence of transport from marine sources on the continental slope. New core data from sites south of Rogue Apron indicate that sandy and muddy turbidites may be correlated at least 150 km south to Trinidad Plunge Pool for the period ~ 4800 yr BP to present. Many of the mud turbidites initially described at Rogue Apron coarsen southward, becoming sandy turbidites. High-resolution Chirp seismic profiles reveal that turbidite stratigraphy along the base of the southern Cascadia continental slope is continuous, with little variation for at least 240 km along strike. The Chirp data show that turbidites along the Cascadia base of slope are ubiquitous, and likely not sourced solely from submarine canyon mouths, but may also have been delivered to the proximal abyssal plain as sheet flows from the open continental slope and coalescing local sources. Regional stratigraphy reveals that hemipelagic sedimentation rates and total Holocene turbidite thickness and mass are similar at widely separated sites, yet the total thickness of the Holocene section is greater by a factor of two in southern Cascadia. This difference is primarily due to the presence of the 21 mud and two additional sandy turbidites. We conclude that the Cascadia mud turbidites are ubiquitous along southern Cascadia only, with only one likely example of a correlated turbidite limited to the northern margin. Eight onshore sites including three marsh sites and five lakes include potential seismogenic correlatives of the southern Cascadia turbidites. In all, the onshore sites may have recorded > 80% of the events attributed to plate boundary earthquakes offshore during the period 0–6000 yr ago. Slope stability calculations suggest that earthquakes of <i>M</i><sub>w</sub> = 7.0 or greater should generate ground accelerations sufficient to destabilize open slopes and canyon heads with or without excess pore fluid pressure. Estimates of Mw for segmented ruptures are in the range of 7.4–8.7, exceeding the slope stability criteria for typical slopes by at least a factor of ~ four.
Reflection seismic data were acquired along a ca. 22 km long profile over the end-glacial Burträsk fault with a nominal receiver and source spacing of 20 m. A steeply dipping reflection can be correlated to the Burträsk fault, indicating that the fault dips at about 55° to the southeast near the surface. The reflection from the fault is rather poorly imaged, probably due to a lateral offset in the fault of about 1 km at this location and the crookedness of the seismic profile in the vicinity of the fault. A more pronounced steeply dipping reflection is observed about 4 km southeast of the Burträsk fault. Based on its correlation with a topographic low at the surface this reflection is interpreted to originate from a fracture zone. There are no signs of large displacements along this zone as the glacial ice receded, but earthquakes could be associated with it today. Other reflections on the processed seismic section may originate from changes in lithological variations in the supra-crustal rocks or from intrusions of more mafic rock. Constraints on the fault geometry provided by the reflection seismic data will help determine what stresses were required to activate the fault when the major rupture along it occurred ca. 9500 years ago.