Can tree-ring chemistry reveal absolute dates for past volcanic eruptions?

Discussion of the significance of volcanically induced impacts on human history, the natural environment, and climate through the Holocene, has frequently stalled because of controversy concerning certain key volcanic eruptions and their precise relationships with the archaeological/environmental record. A major stumbling block in such debates is a failure to obtain precise and accurate dates for many of these key volcanic events. Most existing dates currently float against archaeological, historical, environmental, and climate data. A potential means to resolution lies with tree rings: these can be dated precisely by dendrochronology, are available from a wide range of loci around the world, and can record global climatic influences. It has been suggested that certain growth anomalies in dendrochronological sequences could offer “proxy” absolutely dated records of major, climatically effective, volcanic eruptions. However, this assertion has been widely disputed given the lack of a direct, positive, causal connection. The hypothesis that the required connection may be chemically encoded in individual annual growth rings from dated sequences is explored here both via review of existing literature on dendrochemical techniques, and by LA-ICP-MS chemical analysis of two tree ring sequences. It is concluded that dendrochemistry provides a promising means by which absolute dates may one day be attributed to key volcanic eruptions of pre-modern times.     

DENDROCHRONOLOGICAL DATING OF THE CHIEF JOHN ROSS HOUSE,ROSSVILLE, GEORGIA

Abstract

The Chief John Ross House is a two-story oak (Quercus spp.) and eastern red cedar (Juniperus virginiana L.) log structure located in downtown Rossville, Georgia. The log structure was reportedly built in 1797 by John McDonald, grandfather of Chief John Ross, for his Cherokee bride. This construction date first emerged in the 1950s, when efforts were underway to save the structure. Historical documents, however, indicate that the structure did not exist until 1816. Ross lived at the structure until 1828, when he was elected the last principal chief of the Cherokee before the tribe’s forced removal during the Trail of Tears. Using dendroarchaeological techniques, 28 archaeological (increment) cores were removed from the oak portion of the structure in 2007 to verify the construction date. Cores were processed and dated using the white oak (Quercus alba L.) Piney Creek Pocket Wilderness, Tennessee chronology. Of the 28 cores, 22 (from 19 trees) yielded cutting dates clustered around the winter of 1816–17, indicating the structure likely was not built by McDonald. This construction date does, however, make it possible for Chief John Ross himself to have been the builder. This correction to history should increase public attention and preservation efforts at the structure.     

Construction Features of Doel 1, a 14th‐Century Cog found in Flanders

In 2000, a well‐preserved, c.21 m‐long shipwreck, Doel 1, was found upside‐down in a silted‐up creek near the river Scheldt (Belgium). An interdisciplinary research project was initiated, including 3D registration of all timbers, wood species identification, dendrochronology and archaeobotanical analysis of the caulking material. Doel 1, of which 70% is preserved, displays the construction features of a cog. Unseasoned wood was used and dated by dendrochronology to AD 1325/26. Remarkable features include the symmetrical layout of the bottom planks, the atypical arrangement of the frames to the fore, and evidence of partial dissassembly of the ship after intensive use.     

Chronology and Cultural Activity in Johnson Canyon Cliff Dwellings: Interpretations from Tree-Ring Data

Abstract

Archaeological tree-ring samples were collected during the summer of 1974 from nine cliff dwellings in the tributaries of Johnson Canyon on the Ute Mountain Indian Reservation in SW Colorado. The cliff dwellings belong to the Mesa Verde branch of the Anasazi cultural tradition and on the basis of ceramics and architecture could be assigned to the McElmo phase (1050-1150 A.C.) and the Mesa Verde phase (1150-1300 A.C.). Of a total of 461 tree-ring samples, 352 could be dated. These dates and other observations made during the analysis are applied toward refinement of the dating of the sites as well as to interpretations about utilization of timber resources, environment, and demography. Two clusters of cutting dates consistently occur in most of the sites indicating two periods of construction activity, one in the middle 1100s and the other in the early 1200s. The existing architecture at these sites dates to the early 1200s while the earlier structures have apparently been dismantled and their materials reused. These data suggest an occupation of the area beginning in the 1140s, followed by an abandonment by the 1160s. The area was reoccupied in the early 1200s for only 30 to 40 years before final abandonment.     

Radiocarbon Dating of Architectural Mortar: A Case Study in the Maya Region,Quintana Roo,Mexico

Abstract

The use of radiocarbon dating to analyze mortar and charcoal inclusions within mortar or plaster is a useful way to date the construction of architecture, particularly when options for other chronometric methods are limited. In the Yalahau region of northern Quintana Roo, Mexico, members of the Yalahau Regional Human Ecology Project have faced challenges in dating buildings made of large blocks of stone in the Megalithic architectural style. The Megalithic style poses serious problems for any analysis, as excavating into structures with stones weighing several tons can be dangerous, expensive, and time consuming. Additionally, there are no associated sculptures, texts with dates, or other traditionally accessible chronological markers. These factors have resulted in a reliance on a ceramic chronology despite the uncertainty of the dating of many ceramic types in this region, as well as the questionable contextual associations between recovered ceramics and architectural construction phases. Megalithic-style structures at the ancient Maya site of El Naranjal have residual mortar with charcoal inclusions left behind during the mortar-making processes that can be extracted and dated with AMS ¹⁴C methods. Several samples of mortar and charcoal were obtained from structures 1 and 10 from exposed exterior walls and an interior vault. The resulting dates confirm the date for the construction based on ceramics excavated from the same site.     

PLASTER AND MORTAR RADIOCARBON DATING OF NABATEAN AND ISLAMIC STRUCTURES,SOUTH JORDAN*

The study aims to use lime mortars and plasters to radiocarbon date Nabatean and Islamic structures from Petra and Udruh, south Jordan. Fifteen samples from seven structures were characterized by thin‐section, scanning electron and cathodoluminescence microscopy. The lime binders of all the samples and the organic inclusions from nine samples were AMS radiocarbon dated. The dates and the historical data of the samples were compared with each other. The results showed an agreement between the radiocarbon dates of the lime binders and the organic inclusions and the historical data for most of the samples. The radiocarbon dates of the lime binders supported by the radiocarbon dates of the organic inclusions and the archaeological data were helpful in reconstructing a rather precise chronology of the studied structures.     

Dating of 4th millennium BC pile-dwellings on Ljubljansko barje,Slovenia

We present absolute dates of seven late Neolithic pile-dwellings on Ljubljansko barje, Slovenia. They were settled from ca. 3600 to 3332 (±10) and from 3160 to 3071 (±14) cal BC, as shown by investigations of wood using dendrochronology and radiocarbon wiggle-matching. We defined eleven periods of intensive tree felling (and building activities) and one major settlement gap (when no trees were felled) from 3332 to 3160 cal BC. A major settlement gap presumably also followed after 3071 cal BC (i.e., after the end date of the investigated sites). Our investigations included over 2500 pieces of wood, mainly from the piles on which the dwellings were built. Among important wooden artefacts were a wheel with axle (one of the oldest preserved wheels in the world) and two dugout canoes, all from the settlement phase from 3160 to 3100 cal BC. As shown by parallel studies, the economy in the sites was characterized by copper metallurgy, skilful wood processing and use, cultivation of domestic plants, gathering of wild plants, animal husbandry, hunting and fishing. The settlements were contemporaneous with a number of sites in the north of the Alps, the younger ones coincided with the lifetime of the Neolithic Iceman (Ötzi). Since Ljubljansko barje has a strategic position at the crossroads between western central and (south) eastern Europe the presented absolute dates provide a basis for their comparison with other dated contemporaneous sites (in the west), to revise the chronology of similar sites in the (south) east (which are not yet exactly dated), and to evaluate their interconnection and roles in cultural development in prehistory.     

Dating European Palaeolithic Cave Art: Progress,Prospects, Problems

Over the last decade several dozen direct dates on cave art pigments or associated materials have supplemented more traditional style-based attempts to establish a chronological (and developmental) scheme for cave art. In the “post-stylistic” era an holistic integration of pigment “recipe” analysis, formal stylistic analysis and direct chronometric dating have been applied to a handful of dates. Here, we examine the state-of-the-art of Palaeolithic cave art dating, with particular emphasis on certain radiocarbon and Uranium-series projects. We examine the relative successes and weaknesses of this cutting edge science. We conclude that there are several weaknesses in current applications that are in serious need of addressing. Issues of sample contamination and of the heuristic relationship between materials dated and the production of the art are particularly problematic. It follows that one should at present be very cautious about straightforward interpretations of apparent “dates” of cave art.     

Brush-Piling: Eighteenth Century Engineering in an American Wilderness

Abstract

Old Mill was one of a small group of early silk mills established in East Cheshire during the mid-18th century. It was notable for its size, and for the involvement of James Brindley in its construction. The mill was extended and a beam engine added c. 1830, but it was partially demolished in 1939. In 2003 the remaining structures were demolished, which provided the opportunity for a programme of building recording and excavation. James Brindley's role is examined in terms of the application of water power, and the context of the classical architecture and likely geological provenance of Old Mill is discussed.     

Dendrochronological Dating and Provenancing of Timbers from the Arade 1 Shipwreck,Portugal

As part of a larger project promoting the development of historical dendrochronology in the Iberian Peninsula, ship‐timbers from the Arade 1 wreck (mostly planking and framing elements), stored at the DANS/IGESPAR in Lisbon, were examined. Of these, 52 samples were identified as deciduous oak (Quercus subg. quercus) and two as chestnut (Castanea sativa). Of 24 timbers selected for dendrochronological research, 23 could be dated, placing the origin of the wood in western France and the felling of trees between AD 1579 and 1583. Their homogeneity suggests they are part of the original construction, which probably took place shortly after AD 1583. © 2012 The Authors     

Peterborough Abbey and the Peterborough Psalter in Brussels

Abstract

New investigations at Wenlock Priory serve to allow a reinterpretation of the earlier excavations of Cranage (1901) and of Jackson and Fletcher (1962–3). A number of walls exposed in earlier excavations, and thought to be Saxon, seem to have comprised part of a Roman complex, whose abandonment is represented by a layer of collapsed plaster in the latest work.

The abandoned Roman buildings were re-occupied in the seventh century when a double monastery was founded here. The topography of the site, the location of the two churches and the extent of the monastic precinct are examined.

The plan of the Romanesque church, published by Jackson and Fletcher, and by them dated to before the Conquest, is revised and sculptural evidence, radiocarbon determinations from burials and documentary sources are used to suggest rather that Roger de Montgomery was the builder after the Conquest.     

A Bayesian AMS C chronology of the Classic Maya Center of Uxbenká, Belize

Archaeologists require precise chronologies of cultural change to understand the nature and timing, and causes and effects, of ecological and social transformations. The Uxbenká Archaeological Project (UAP) has made chronology building a main goal, employing epigraphic data, artifact seriation, and high-precision AMS ¹⁴C dating. With more than 60 ¹⁴C dates with measurement errors below ±25 ¹⁴C yr, primarily on single charcoal specimens, Uxbenká may be the most intensively dated Classic Period site in the tropical Maya Lowlands. Here we take the next step, combining this rich chronometric dataset with associated stratigraphic information in OxCal's Bayesian framework to generate a high-resolution chronology of Uxbenká's early development and expansion in southern Belize. We show how archaeologists may take advantage of complex architectural stratigraphy to constrain broad calibrated ranges during the Classic Period, and to estimate dates for observed construction events that can not be directly dated (e.g., clearing/leveling plazas, laying plaster floors, renovating/rebuilding structural elements). Our analysis confirms the antiquity of the ceremonial Stela Plaza (Group A), where first construction is estimated between 60 cal BC and cal AD 220 and is associated with a Pre-Classic structure obscured by later construction and reorientation of the group to a N-S alignment ca. AD 150–310. The analysis also indicates initial leveling and construction at plaza Group B from cal AD 60–310 and Group D from cal AD 20–240, both earlier than previously assumed. Though Late Classic contexts are not as well represented by direct dates, architectural modifications are documented at all three plaza groups after AD 550, including the extensive plastering, laying paving stones, and construction of facades on existing structures. The resulting chronology revises our previous thinking on the mode of settlement and development of Classic Maya society at Uxbenká and indicates specific areas of investigation to elucidate events in the Late and Terminal Classic at the site, including political and social fragmentation and the abandonment of the urban core late in the Classic Period.     

On the Glazing of the North Rose Window of Lincoln Cathedral

Upton Court (Pl. VIIA) is a timber-framed open hall house, dated by dendrochronology to c. 1330. The building appears to have been the work of Merton Priory, the holders of the manor of Upton from the twelfth century until the Dissolution. As originally built the house comprised an ailsed hall range and a jettied upper end cross wing. The open hall truss is of particular interest in that it is a hammer beam variant of unusual construction. The building was recorded by the Threatened Buildings Section of the Royal Commission on the Historical Monuments of England prior to, and in the course of, an extensive programme of alterations and restorations.     

A STATISTICAL APPROACH TO THE CALIBRATION OF FLOATING TREE-RING CHRONOLOGIES USING RADIOCARBON DATES

The bristlecone pine tree-ring calibration of radiocarbon dates, while necessitating changes of up to 700 years in Holocene chronology before 1000 b.c. , offers possibilities of very accurate dating when ¹⁴C determinations from floating tree-ring chronologies are utilized. A statistical approach assuming linear regression is developed and used to position the floating tree-ring chronologies at Swiss neolithic sites, using radiocarbon dates published by Ferguson, Huber and Suess and by Suess. The statistical method gives objective estimated dates with estimates of error related, in a consistent and explicit manner, to the inherent inaccuracies of the radiocarbon dates. Most of the method may readily be tested by standard statistical procedures. For the particular cases considered the assumptions of linearity and parallelism are investigated, and the precision of the estimated dates is comparable with that claimed by Suess and his co-workers. A precise calibration is thus possible without utilizing the short-term fluctuations in the Suess calibration curve. The analysis, while avoiding some assumptions of Suess and his collaborators, offers an explicit procedure for establishing controlled teleconnections with the Ferguson dendrochronology, and supports their emphasis on the importance of radiocarbon dates from floating tree-ring sequences for the construction of precise prehistoric chronologies.     

The integration of chronological and archaeological information to date building construction: an example from Shetland,Scotland, UK

This paper presents new chronological data applied to the problem of providing a date for the construction of a prehistoric building, with a case study from the Old Scatness Broch, Shetland. The innovative methodology employed utilises the combination of radiocarbon and optically stimulated luminescence (OSL) dates with the archaeological information, which includes the stratigraphic relationships of sampled deposits, context information, and evidence relating to the formation of the deposit. This paper discusses the scientific validity of the dates produced, and the advantages that the methodology employed at this site offers for archaeological interpretation. The combined dating evidence suggests that the broch at Old Scatness is earlier than the conventionally accepted dates for broch construction. More broadly it shows the value of integration of the specialists at the planning stages of the excavation. The application of a Bayesian statistical model to the sequences of dates allowed investigation of the robustness of the dates within the stratigraphic sequences, as well as increasing the resolution of the resulting chronology. In addition, the value of utilising multiple dating techniques on the same deposit was demonstrated, as this allowed different dated events to be directly compared as well as issues relating to the formation of the sampled deposit. This in turn impacted on the chronological significance of the resulting dating evidence, and therefore the confidence that could be placed in the results.     

Edward II. His Last Months and his Monument

Abstract

Very little site-oriented dendrochronology has been undertaken in Scotland, possibly because of the absence of a locally based dendrochronological facility until recently. However, timbers found during the excavations of several medieval burghs in the late 1970s and 1980s were saved for future analysis and had been stored in museums around the country. During a project to locate suitable samples fir a Scottish tree-ring database the potential of these assemblages was recognised. Although relatively small assemblages, their analysis has expanded and strengthened the tree-ring database within Scotland, thus facilitating future work. Evidence fir synchronous development in the early burghs in the late 12th century and the nature of the woodland resource at times during the medieval period is presented. An 'event horizon' in the early 10th century, signalled by the birth dates of marry of the dated timbers, has been recognised and possible causes are discussed. The projects reported on here were all funded by Historic Scotland.     

Chronostratigraphy of an Eroding Complex Atlantic Round House,Baile Sear,Scotland

A high-resolution chronostratigraphy has been established for an eroding Atlantic round house at Sloc Sàbhaidh (North Uist, Scotland), combining detailed OSL profiling and dating of sediments encompassing the main bracketing events associated with the monument, radiocarbon AMS dates on bone recovered from excavated features and fills within it, and TL dates on pottery and burnt clay. Concordant OSL and radiocarbon evidence place construction of the wheelhouse in the first to second centuries AD, contemporary with dates from the primary occupation. Beneath the wheelhouse, clay deposits containing burnt material, attest to cultural activity in vicinity to the monument in the preceding second to first centuries BC. At a later date, the southern wall collapsed, was rebuilt, and the interior spaces to the monument re-structured. The chronology for the later horizons identified from the sediment luminescence dates extends to the second half of the first millennium AD, which goes beyond the range of the radiocarbon dates obtained. The data from ceramics encompass both periods. The juxtaposition of the dating evidence is discussed relative to short and longer chronologies for this Iron Age monument. Corollaries of this research are the implications that based on the long chronology, some of the ecofacts (bone) appear to be residual, and that the temporal duration of Hebridean Coarse Ware may extend into the second half of the first millennium AD.     

Archeoseismicity and environmental crises at the Sialk Mounds,Central Iranian Plateau,since the Early Neolithic

During the long-lasting cultural sequences of the Shurābeh and Sialk archeological mounds (6200–550 BC) the inhabitants encountered numerous diversified crises along a narrow fertile passageway at the edge of the Central Iranian Plateau Great Desert. Some of the threats may be attributed to earthquakes, drastic climatic changes, and man-made environmental deterioration, which possibly led to the settlement withdrawing at different stages toward a more suitable location. Our study identified the occurrence of a large-magnitude earthquake around 3800 BC along the Kāshān fault, which is well-documented by various lines of circumstantial evidence, including: (i) numerous contemporaneous smashed skeletons and artifacts underneath collapsed walls and ceiling debris in several different areas; (ii) tilted and collapsed walls; (iii) nearly N–S oriented fallen large storage jars; and (iv) nearly vertical deep ground fractures cutting walls and floors of the Sialk III₅ South Mound settlement. Archeological data also shows additional stratigraphic discontinuities and damages that may be attributed to earthquakes. However, damage features in limited exposed trenches are less conclusive and require additional careful excavations. Apparent ancient paleo-architectural innovative attempts to enhance the coherency/elasticity of the structures and minimize earthquake damage to buildings were also noted, suggesting the indigenous earthquake hazard mitigation endeavor. There seems to be a correlation between some site abandonment dates and possible drastic regional draught/cooling events. The natural and anthropogenic impacts addressed in this study constituted major threats to the sensitive archeological settlements at the fringe of the desert and the vicinity of the Kāshān active fault since antiquity.     

The Planking Clamp from Tårnby: a Medieval Danish Boatbuilding Tool

At the bottom of a well on a medieval farm on the Danish island of Amager, archaeologists found a planking clamp dated by dendrochronology to 1405 AD. ¹ The clamp is of great importance: very few examples have been found or recognised in Northern Europe to date, and this is the best preserved, and thus provides data about its shape and use; and the size of boat it was used in the construction of. It is discussed whether the clamp was used exclusively for boatbuilding or whether it might also have been used in other crafts. It is suggested that copies of the Tårnby planking clamp might be used in future experimental boatbuilding projects.
© 2004 The Nautical Archaeology Society