Variability of laboratory procedures and results in geoarchaeology

Many laboratory techniques are available to geoarchaeologists to determine physical or chemical attributes of sediment or soil samples, and several techniques are often available for analysis of a single attribute. This is illustrated by analyzing duplicate sediment and soil samples from the British Camp Site (Washington) and Lubbock Lake Site (Texas) using two methods for organic carbon content, two methods for organic matter content, and three methods for calcium carbonate content, and several pretreatment procedures for particle-size analysis. These comparisons illustrate that different methods of analysis for the same property of duplicate samples can yield different results. Therefore, when making comparisons with data from other sites or other investigators, the types of laboratory methods used in geoarchaeological analyses are important considerations. Choice of a particular technique will depend on a variety of factors, often conflicting, including the archaeological and geoarchaeological questions being asked, the physical and chemical nature of the samples, and the accuracy, efficiency, and cost of the method.     

Multi-proxy geoarchaeological study redefines understanding of the paleocoastlines and ancient harbours of Liman Tepe (Iskele, Turkey)

Determining the position of Liman Tepe's (ancient `Clazomenae') archaeological features relative to the coastline is important for understanding their intended function and reconstructing the character of Aegean maritime activities and sea-based trade. Previous attempts at reconstructing harbour locations at Liman Tepe relied on extrapolating paleoenvironments based on modern surface topography. In light of this, samples from a sediment coring survey and terrestrial and underwater archaeological excavations were analysed using multi-proxy geoarchaeological methods to determine paleoenvironmental facies. Micropaleontological (foraminifera), sedimentological (grain-size analysis) and geochemical (δ¹³C/δ¹⁸O) analyses resulted in the reconstruction of the coastal paleogeomorphology, including the presence and absence of ancient harbouring areas. Neither of the previous coastal reconstructions was supported by the new results. Instead, two separate harbouring areas were recognized, one coincident with the Early Bronze Age (4800–3900 years bp) and a second during the archaic and classical periods ( c. 2800–2400 years bp). These results emphasize the necessity for multi-proxy geoarchaeological studies when approaching coastal archaeological sites as a means to reconstruct paleocoastal geomorphology and understand ancient maritime development better .     

River channel evolution and tsunami impacts recorded in local sedimentary archives – the ‘Fiume Morto’ at Ostia Antica (Tiber River,Italy)

Ostia, the ancient port of Rome at the mouth of the river Tiber (Italy), flourished until the 2nd Century ad , although massive siltation had already caused the abandonment of its lagoonal harbour in the 1st Century bc . In search of an alternative harbour site, geomorphological and geoarchaeological research was carried out in the ‘Fiume Morto’, an abandoned Tiber meander to the immediate north of the town. To reconstruct its complex development and evaluate the suitability of the river channel as a fluvial harbour, a transect perpendicular to the former river channel's flow axis was systematically explored by a new methodological approach combining electrical resistivity tomography, direct push-electrical conductivity sensing and vibracores. Together with microfossil, mineralogical and geochemical analyses of sediment samples and 50 radiocarbon dates, in-depth stratigraphic data support a detailed reconstruction of different Tiber channel generations. Results reveal a meander development closely related to distinct ‘cut and fill’ dynamics. Inactive river channels were repeatedly filled with lagoonal sediments, abruptly followed by phases of intense incision. Yet, the overall Fiume Morto channel structure remained stable and almost in situ over centuries, showing nearly no lateral changes since the southward shift of the Tiber River mouth in the first millennium bc . In the 1st Century bc , channel conditions favoured navigation and transportation of goods with large ships. Open-water conditions, suitable for anchoring and landing activities, dominate from the 1st Century ad until 1557 ad , when the Fiume Morto meander was finally cut off and silted up within a short time. Within the fluvial deposits, sediments most likely related to tsunami inundations are preserved. These events occurred sometime before the 2nd Century bc , in the early 1st Century ad and in the 17th Century ad or later. Results are consistent with traces of tsunami influence found in Ostia's western lagoonal harbour.     

Geoarchaeological study of the Phoenician cemetery of Tyre‐Al Bass (Lebanon) and geomorphological evolution of a tombolo

The geoarchaeological record of the Phoenician necropolis of Al Bass (Lebanon) provides information concerning the geomorphological evolution of a late Holocene tombolo. Physical and chemical analysis of sediments indicates that the cemetery (9th century B.C.) was located near a littoral lagoon, between the dunes of a cuspate spit pointing toward the island of Tyre. From the sea apex of this spit, the moles mentioned in historical chronicles were constructed. Once mainland and island were connected, at the northern coast (where the port of Sidon was located), a sediment trap was formed, which quickly filled with silt. Afterwards, an extensive field of sand dunes buried all the archaeological remains from Phoenician to Roman times. © 2008 Wiley Periodicals, Inc.     

Palaeoenvironmental record of glacial lake evolution during the early Holocene at Sokli,NE Finland

The development of a glacial lake impounded along the retreating, northeastern ice margin of the Fennoscandian Ice Sheet during the last deglaciation and environmental conditions directly following the early Holocene deglaciation have been studied in NE Finland. This so‐called Sokli Ice Lake has been reconstructed previously using topographic and geomorphologic evidence. In this paper a multiproxy approach is employed to study a 3‐m‐thick sediment succession consisting of laminated silts grading into gyttja cored in Lake Loitsana, a remnant of the Sokli Ice Lake. Variations in the sediment and siliceous microfossil records indicate distinct changes in water depth and lake size in the Loitsana basin as the Sokli Ice Lake was drained through various spillways opening up along the retreating ice front. Geochemical data (XRF core‐scanning) show changes in the influence of regional catchment geochemistry (Precambrian crystalline rocks) in the glacial lake drainage area versus local catchment geochemistry (Sokli Carbonatite Massif) within the Lake Loitsana drainage area during the lake evolution. Principal component analysis on the geochemical data further suggests that grain‐size is an additional factor responsible for the variability of the sediment geochemistry record. The trophic state of the lake changed drastically as a result of morphometric eutrophication once the glacial lake developed into Lake Loitsana. The AMS radiocarbon dating on tree birch seeds found in the glaciolacustrine sediment indicates that Lake Loitsana was deglaciated sometime prior to 10 700 cal. a BP showing that tree Betula was present on the deglaciated land surrounding the glacial lake. Although glacial lakes covered large areas of northern Finland during the last deglaciation, only few glaciolacustrine sediment successions have been studied in any detail. Our study shows the potential of these sediments for multiproxy analysis and contributes to the reconstruction of environmental conditions in NE Finland directly following deglaciation in the early Holocene.     

Marine inundated archaeological sites and paleofluvial systems: examples from a karst-controlled continental shelf setting in Apalachee Bay,Northeastern Gulf of Mexico

Underwater geoarchaeological research in Apalachee Bay, in the northeastern Gulf of Mexico off northwest Florida, has enabled the reconstruction of portions of the karst-controlled paleodrainage system, the discovery of several inundated prehistoric archaeological sites, and the exposure of sediments accumulated during the drowning of the continental shelf. Diagnostic artifacts discovered at the sites included chipped stone tools and debitage indicating Paleoindian, Early Archaic, and Middle Archaic occupation. A geoarchaeological model using terrestrial analogs was used to locate and investigate inundated sites. Methods employed include seismic profiling, vibracoring, diver tow surveys, diver collection transects, and induction dredge excavations. We document evidence for sea-level rise, related environmental succession and site formation processes for indundated prehistoric sites in the Apalachee Bay region from approximately 8000 to 6000 yr B.P. © 1997 John Wiley & Sons, Inc.     

Late Weichselian to early Holocene litho- and biostratigraphy in the Devil's Hole area,central North Sea,and its relation to glacial isostasy

The 6-m-long British Geological Survey vibrocore 56+01/170 from the Devil's Hole area, central North Sea, comprises glaciomarine and marine sediments of Late Weichselian and Holocene age. Besides the foraminiferal, pollen and AMS ¹⁴C data presented in this study, amino acid and ostracod data exist for the core. The accumulation of the sediment in the core began ca. 15.7 ¹⁴C ka BP on an erosional surface on overconsolidated Saalian sediment. When the lower part of the core (facies 1) accumulated the core area is interpreted to have been around 40 m lower than present. This interpretation is based on two assumptions; first, that the sediment is now ca. 20 m above the global sea level at the time of deposition, and second, that the marine microfaunal content reflects a water depth of about 20 m at that time. Crustal downflexure caused by Late Weichselian glacial loading of the core area is considered as the most plausible explanation of this difference. Glacial overriding would also explain the overconsolidation of the underlying Saalian sediment, the erosional surface on the Saalian sediment and the absence of Weichselian sediment older than ca. 15.7 ka BP at the core site. Indications of a regressional trend, with a minimum age of 12.1 ka BP, support the suggestion that the Devil's Hole area was glaciated during the Weichselian, as the fall in sea-level at that time probably reflects local isostatic rebound.     

GIS morphometric indicators for the analysis of sediment dynamics in mountain basins

Watershed management and headwater reconstruction programs require a reliable knowledge of sediment dynamics. Geographical Information Systems (GIS) provide the framework for the implementation of different complex techniques for the assessment of shallow landsliding and erosion processes in mountain basins. This paper presents some morphometric indicators aimed at erosion and sediment delivery analysis. The proposed indicators can be easily derived from medium to fine resolution Digital Elevation Models (DEM). Applications conducted in Eastern Italian Alps have shown the adequateness of the proposed approach to address erosion and sediment-related problems. The analysis considered the classification of sediment source areas with regard to their activity, the comparison between drainage basins having different morphological characteristics and the topographic control on sediment transport capacity, with a particular attention to the identification of channel reaches characterised by a low sediment transport capacity.     

基于定量古地理的BQART模型深时古地势重建方法

源—汇系统分析下的古地势重建是当前沉积学领域的一个热点方向。古地势重建对于理解区域构造演化、气候变化、地表风化、物源供给及其相互关系具有重要作用。BQART沉积通量模型提供了入海流域中沉积通量与地质背景B、水流量Q、流域面积A、最大地势高度R、年均温度T之间的经验关系,逐渐发展为深时尺度下古流域地势重建的重要工具。本文在综合层序—古地理、旋回地层学、古水文比例关系和古地貌比例关系等方法的基础上,提出基于定量古地理的BQART模型深时古地势重建方法,结合沉积体积回填法可进一步获得构造抬升幅度与速率。通过该方法获得峨眉山大火成岩省内带古地势在晚二叠世期间持续缓慢上升,至晚二叠世末达200余米,累计构造抬升幅度约500~750 m。该深时古地势方法适用于气候温暖湿润、构造相对稳定条件下的中大型外流盆地,对能源盆地的勘探开发具有重要意义。     

Review of the Analysis and Application of Diatoms in the Marine Sediments

With regard to the analysis and application of diatoms in the marine sediments, diatom purification method, data analysis method and diatom application in environmental reconstruction were summarized. The diatom purification is composed of four main processes (removing calcium carbonate, organic and minerogenic matter, and slide preparation). For each process, frequently used methods and improvements were introduced, while their pros and cons were compared. As to the data analysis, in order to ensure statistical reliability, the essential methods and principles were represented in detail with species identification and counting, data expression and error estimation involved to reduce errors as much as possible. On this basis, the numerical method application was explained for its advantage of improving the accuracy for analysis. The applications of diatom fossils in environmental reconstruction were studied more deeply abroad, including the investigation of relationship between diatom fossils and upper-water environment, the application of diatoms from deeper core sediment for reconstructing oceanic paleoenvironment, tracing salinity and reflecting eutrophication. As far as the deficiency of the domestic research was concerned, multidisciplinary technologies and observational data were suggested to be combined into the study in order to promote the quantitative research of diatom fossils and the accuracy of environmental reconstruction.     

Sand,hearths, lithics and a bit of bioturbation: Site formation processes at Umhlatuzana rockshelter,South Africa

Umhlatuzana rockshelter is known for its continuous record of Middle and Later Stone Age lithic assemblages. This study presents multiproxy geoarchaeological data (micromorphology, X-ray diffraction and scanning electron microscopy with energy-dispersive spectroscopy) to reconstruct the depositional and post-depositional history of the site. Although the Stone Age deposits macroscopically appear homogeneous, micromorphological analysis reveals the existence of primary, unaltered depositional microlayering throughout the sequence. Sediments related to combustion activities on-site are observed in both the Holocene and Pleistocene deposits. Post-depositional geochemical alterations result in the formation of several phosphatic minerals that significantly affect the site's preservation conditions. One of those is vashegyite, a rare magnesium phosphate mineral related to acidic and moist sedimentary environments. Bioturbation features are prominent at the microscale, but sediment mixing does not seem to affect the vertical distribution of the artifacts. The observation of horizontal microlayering in both the Pleistocene and Holocene illuminates the dominant mechanism of sedimentation throughout the site's 70,000-year occupational history. It moreover shows that the lithics can be analysed as coherent assemblages.     

河南省内黄县河流地质考古研究

河流地质考古学是基于地层研究河流和考古遗址之间关系的学科.近年来我们在河南省内黄县开展的河流地质考古研究揭示了黄河复杂的演化历史,在此基础上进一步探讨了古代人类活动与周围环境的相互作用.本文主要介绍了2010~2016年我们在河南省内黄县3个全新世遗址(岸上、三杨庄和大张龙村)的地质考古工作中所取得的成果.研究区域内遗址的地层记录表明,许多考古遗址被深埋于地下,并可能影响了3000 a B.P.以来的河流沉积过程.我们在岸上遗址发掘了A、B、C、D共4处青铜时代的沟渠遗迹,这些沟渠的堆筑可能影响了后期的沉积过程并导致了遗址周边微地貌的改变;在三杨庄遗址识别出了多层不同时期的人为古土壤,包括新石器晚期、战国时期、汉代和唐代;在大张龙村发现了北宋时期黄河泛滥沉积物,其沉积过程可能受周边村落遗址的影响.根据测得的14C年代和沉积层厚度,本研究进一步对这3处遗址的沉积速率进行了估算,并与前人对华北平原沉积速率的相关研究进行了对比.结果表明,这3处遗址所显示的沉积速率自3000 a B.P.开始显著增加,与对早期历史时期黄河河道沉积速率的估算结果相吻合.因此,基于遗址的地质考古研究能够为探索人与环境的互动关系提供大量信息.未来的工作中,我们需要开展更多基于考古遗址的河流地质考古研究,以深入探讨华北平原的自然沉积过程与文明演进过程之间的关系.     

Chemical weathering over the last 1200 years recorded in the sediments of Gonghai Lake,Lvliang Mountains,North China: a high‐resolution proxy of past climate

Increasing interest in global climate change has led to attempts to understand and quantify the relationship between chemical weathering processes and environmental conditions, especially climate. This interest necessitates the identification of new climate proxies for the reconstruction of two important Earth surface processes: physical erosion and chemical weathering. In this study, an AMS ¹⁴C‐dated 2.8‐m‐long sediment core, GH09B1, from Lake Gonghai in north‐central China was subjected to detailed geochemical analyses to evaluate the intensity of chemical weathering conditions in the catchment. Multivariate statistical analysis of major and trace elemental data of 139 subsamples revealed that the first principal component axis PCA1 explained ～53% of the variance in the assemblage of elements/oxides with significant positive correlations between PCA1 scores and the separation of mobile and soluble elements/oxides from the immobile and resistant elements/oxides, which is thus able to indicate the chemical weathering in the catchment. These results are supported by the down‐core trends of other major and trace elemental ratios of chemical weathering intensity as well as by pollen data from the same core. Variations in PCA1, chemical index of alteration (CIA), Rb/Sr ratio and other oxides ratios indicate stronger chemical weathering due to a wet climate during the Medieval Warm Period (MWP). However, the MWP was interrupted by an interval of relatively weaker chemical weathering conditions from AD 940–1070. Weak chemical weathering under a dry climate occurred during the Little Ice Age (LIA), and increased chemical weathering intensity during the Current Warm Period (CWP). Our proxy records of chemical weathering over the last millennium correlate well with the available proxy records of precipitation from Gonghai Lake as well as with the speleothem oxygen isotope record from Wanxiang Cave, but do not show a significant correlation with the temperature record in N China, suggesting that the chemical weathering intensity in the study area was mainly controlled by the amount of rainfall rather than by temperature. We conclude that high resolution lacustrine sediment geochemical parameters can be used as reliable proxies for climate variations at centennial‐decadal time scales.     

Development of water management strategies in southern Mesopotamia during the fourth and third millennium B.C.E.

The last two decades witnessed increasing scholarly interest in the history of water management in southern Mesopotamia. Thanks to many geoarchaeological research projects conducted throughout the central and southern Iraqi floodplains, a general understanding of the macrophases of anthropogenic manipulation of this vast hydraulic landscape has been achieved. However, current narratives mostly rely on studies at a regional scale and are based on excessively long chronological phases (often spanning a whole millennium). A finer-tuned analysis at a submillennial scale is needed to better appreciate the dynamics that led to the development of artificial canals and irrigation systems and the creation of harbours in cities and other navigation-related facilities. The Iraqi-Italian QADIS project is addressing this issue through a systematic geoarchaeological investigation in the south-eastern area of the Qadisiyah province. We aim to update the current narrative by analysing case studies involving specific periods of occupation. We performed 17 boreholes to propose a date on the functioning period of the hydraulic works in five selected archaeological sites of this region. This approach allowed us to understand changes in water management strategies in both the short and the medium term (i.e., on a scale of centuries). In this paper, we present the results for the fourth and third millennia B.C.E. This period witnessed a crucial passage from the basic exploitation of natural watercourses for irrigation and occasional navigation to the emergence of the first system of artificial canals and intraurban harbours.     

Mössbauer spectroscopic studies on the iron forms of deep-sea sediments

Mössbauer spectroscopy was applied to characterize the valence states Fe(II) and Fe(III) in sedimentary minerals from a core of the Peru Basin. The procedure in unraveling this information includes temperature-dependent measurements from 275?K to very low temperature (300?mK) in zero–field and also at 4.2?K in an applied field (up to 6.2?T) and by mathematical procedures (least-squares fits and spectral simulations) in order to resolve individual spectral components. The depth distribution of the amount of Fe(II) is about 11% of the total Fe to a depth of 19?cm with a subsequent steep increase (within 3?cm) to about 37%, after which it remains constant to the lower end of the sediment core (at about 40?cm). The steep increase of the amount of Fe(II) defines a redox boundary which coincides with the position where the tan/green color transition of the sediment occurs. The isomer shifts and quadrupole splittings of Fe(II) and Fe(III) in the sediment are consistent with hexacoordination by oxygen or hydroxide ligands as in oxide and silicate minerals. Goethite and traces of hematite are observed only above the redox boundary, with a linear gradient extending from about 20% of the total Fe close to the sediment surface to about zero at the redox boundary. The superparamagnetic relaxation behavior allows to estimate the order of magnitude for the size of the largest goethite and hematite particles within the particle-site distribution, e.g. ～170?Å and ～50?Å, respectively. The composition of the sediment spectra recorded at 300?mK in zero-field, apart from the contributions due to goethite and hematite, resembles that of the sheet silicates smectite, illite and chlorite, which have been identified as major constituents of the sediment in the <2?μm fraction by X-ray diffraction. The specific “ferromagnetic” type of magnetic ordering in the sediment, as detected at 4.2?K in an applied field, also resembles that observed in sheet silicates and indicates that both Fe(II) and Fe(III) are involved in magnetic ordering. This “ferromagnetic” behavior is probably due to the double-exchange mechanism known from other mixed-valence Fe(II)–Fe(III) systems. A significant part of the clay-mineral iron is redox sensitive. It is proposed that the color change of the sediment at the redox boundary from tan to green is related to the increase of Fe(II)–Fe(III) pairs in the layer silicates, because of the intervalence electron transfer bands which are caused by such pairs.     

沉积植物古DNA技术在古植被重建中的应用

近些年基因测序技术的大量应用为沉积物中植物古DNA的分析提供了技术支撑,将古植被重建的技术发展到了分子层面。国内外相关研究表明,来源于沉积体系中的沉积植物古DNA（Sediment plant ancient DNA, aDNA）可作为古植被重建的有效工具。从技术基础理论、文献计量统计、发展应用及实验操作几个方面对沉积植物aDNA技术进行了全面的介绍。沉积aDNA技术在植物群落分析上是一个新的补充方法,它可以提供更高的分辨率以及更精确的丰度估算,然而在实验体系及数据库方面还需要不断完善成熟,其在未来将成为古植被重建重要的辅助技术手段。     

Sensitivity of the Eastern Mediterranean geomorphic system towards environmental change during the Late Holocene: a chronological perspective

Alluvial and colluvial sediment deposition provide a vital record of environmental change during the Holocene. Firm chronological control on these archives is necessary to enable us to relate sediment dynamics to human activity and climate variability. In the Eastern Mediterranean, such relationships are hard to establish due to the lack of spatially well‐distributed sediment archives with good chronological control. This scarcity is problematic with respect to regional‐scale reconstructions of the temporal variation of sediment dynamics. Here, we present a radiocarbon database (n = 178) of geomorphological activity collected from multiple distinct sediment archives within the territory of Sagalassos in south‐western Turkey. The data were grouped according to their sedimentary facies for analysis using cumulative probability distributions (CPDs) and sedimentation rate (SR) modelling. Two small‐scale colluvial valleys, where chronological information was abundant, were investigated in more detail. Results show that sedimentation chronology differs between individual, nearby cores, as it depends strongly on the local geomorphic situation. A generalizing approach combining multiple core results yields more widely valid conclusions. High sedimentation rates coincided with the initial major anthropogenic disturbance of the landscape and decreased afterwards, probably due to hillslope soil depletion. CPD and SR analysis indicates that in general colluvial sedimentation rates did not change much from 2000 BC onwards. River floodplain sedimentation, in contrast, increased markedly during the first millennium BC and during recent times, and a significant time lag in enhanced sediment deposition between the upper and lower reaches of the river valleys was observed. Copyright © 2012 John Wiley & Sons, Ltd.     

Geostatistical and multi‐elemental analysis of soils to interpret land‐use history in the Hebrides,Scotland

In the absence of documentary evidence about settlement form and agricultural practice in northwest Scotland before the mid‐18th century, a geoarchaeological approach to reconstructing medieval land use and settlement form is presented here. This study applies multielemental analysis to soils previously collected from a settlement site in the Hebrides and highlights the importance of a detailed knowledge of the local soil environment and the cultural context. Geostatistical methods were used to analyze the spatial variability and distribution of a range of soil properties typically associated with geoarchaeological investigations. Semivariograms were produced to determine the spatial dependence of soil properties, and ordinary kriging was undertaken to produce prediction maps of the spatial distribution of these soil properties and enable interpolation over nonsampled locations in an attempt to more fully elucidate former land‐use activity and settlement patterns. The importance of identifying the spatial covariance of elements and the need for several lines of physical and chemical evidence is highlighted. For many townships in the Hebrides, whose precise location and layout prior to extensive land reorganization in the late 18th–early 19th century is not recoverable through plans, multi‐elemental analysis of soils can offer a valuable prospective and diagnostic tool. © 2007 Wiley Periodicals, Inc.     

Geoarchaeology of the Cerro La China locality (Buenos Aires,Argentina): Site 2 and site 3

Cerro La China, within the Tandilia Range, has a long archaeological record in which three different human occupations were identified. The geoarchaeological approach allowed us to correlate the archaeosedimentary columns at Site 2 and Site 3 and place the local stratigraphy in a regional context. The archaeologically rich stratigraphic sequence is composed of three episodes of loess deposition. The first bears a 10,600 yr B.P. Paleoindian occupation with Fishtail or Fell's Cave Stemmed points. It is followed by a soil-forming interval which ended about 5000 yr B.P. with an erosive episode. The second event of loess deposition continued through an unknown span of time until a new soil-forming interval started; it includes triangular stemless medium size projectile points corresponding to a different human group. By the sixteenth century another erosive event interrupted the soil-forming interval. After this, the third short-term eolian episode occurred and bears the most recent archaeological occupation marked by small triangular stemless points.