The role of scour in shipwreck site formation processes and the preservation of wreck-associated scour signatures in the sedimentary record – evidence from seabed and sub-surface data

Fully submerged shipwreck sites act as open systems, with the exchange of material (sediment, water, organic and inorganic objects) and energy (wave, tidal, storm) across system boundaries. Formation processes at wreck sites are driven by some combination of chemical, biological and physical processes, with physical processes dominant in initial phases of site formation. Scouring and associated depositional patterns that form in response to hydrodynamic forcing are commonly the dominant physical processes acting at shipwreck sites. Scour is initiated by the introduction of a shipwreck to the seafloor, leading to increases in flow velocity and turbulent intensity around the structure. Near-field and far-field scour pits form at wreck sites due to the interaction of horseshoe and lee wake vortices with the mobile substrate. The morphology of resultant scour signatures are controlled by the orientation of the wreck structure in relation to the prevailing hydrodynamic regime, the morphology and size of the wreck and individual site components, the hydrodynamic regime (currents, waves or combined waves and currents), bathymetry and the geology of the site (seafloor and sub-surface conditions). Individual objects or artefacts may act as nuclei to promote scour at a local scale. Under high-energy conditions, groups of artefacts and/or disarticulated structural components emanating from a wreck may compound natural scour processes by rolling or sliding. Under suitable environmental conditions, wreck-associated scour features can be preserved in the sedimentary record.     

The role of time-lapse bathymetric surveys in assessing morphological change at shipwreck sites

Data from time-lapse single-beam and multi-beam bathymetric surveys are used to assess the rate and scale of morphological change at shipwreck sites caused by anthropogenic forcing. The technique is illustrated by characterizing changes in wreck site morphology over two sites located on the east coast of Ireland – the Drogheda Boat site on the River Boyne and the Arklow Bank site in the Irish Sea. Results indicate that repeated bathymetric surveys accurately and rapidly capture morphological change, with time-lapse accretion–erosion models indicating possible erosion rates of up to 0.04 m per day and accretion rates of 0.36 m per day at dynamic riverine and marine sites in response to external triggers. These data are valuable in understanding site formation processes at fully submerged archaeological sites and in the derivation of high-resolution site formation models.     

What is past is prologue: excavations at the Econfina Channel site,Apalachee Bay,Florida, USA

Offshore submerged sites can retain valuable data concerning many questions of interest to archaeology, including what form coastal occupations may have taken during periods before the establishment of modern coastlines and late Holocene climate and ecological conditions. However, submerged offshore sites experience postdepositional forces entirely unlike those in terrestrial contexts, including erosion/deflation of sediments, and degradation of artifacts and/or features caused by the marine environment. Methodological and theoretical approaches to assessing submerged marine sites, versus terrestrial ones, must be adjusted accordingly to extract valuable data and interpretations from them. This study demonstrates the application of these different approaches at the Econfina Channel site (8TA139) in Apalachee Bay, Florida, USA. The site appears to contain significant evidence for coastally adapted occupation during the final part of the Middle Archaic period (～8600–5000?cal?BP), but we needed to address marine site formation processes before we could assess human activities at the site. Sedimentological and archaeological traces of human activities can be teased out using geoarchaeological methods, which differentiate between nonhuman postdepositional processes and the cultural material remains left behind by those who used the site before it was abandoned and subsequently submerged.     

Process-based models for port evolution and wreck site formation at Mombasa,Kenya

Mombasa Island, settled for almost 2000 years, played a central role in the development of the central seaboard of East Africa, emerging by the 16th century as a centre of sustained port dominance. Marine geoarchaeological surveys were conducted in Mombasa Harbour in 2001 (i) to quantify the nature and extent of the submerged archaeological resource, (ii) to investigate site formation and preservation potential of historic shipwrecks, and (iii) to explore the natural evolution of the Old Port and adjacent basins in the context of hydrodynamic and sedimentary processes. Backscatter and single-beam echo-sounder data were acquired, interpreted and diver-truthed using surface-demand and SCUBA systems. It is proposed that sustained scour processes, resultant from the interaction of ebb and flood tidal currents with bedrock ridges, control the bathymetric evolution of Mombasa Harbour, negating requirement for mechanical dredging. The submerged archaeological resource in the area comprises fish traps and shipwrecks. Physical processes govern shipwreck site formation, with scour and bed-migration dominant, ultimately leading to structural instability and site degradation. The wreck of Santo António de Tanná (1697) has been subject to gravitational collapse and mass down-slope movement of material, concentrating wreck structure and material along the portside stern third of the vessel.     

降雨对陕西省榆林市榆阳区明长城破坏的初步分析

降雨是陕西省榆林市榆阳区明长城的主要破坏因素之一。调查中发现,降雨对遗址破坏严重。为了研究降雨对遗址的破坏,在对遗址详细调查的基础上,结合遗址特征与遗址区降雨特点,并参考土壤侵蚀学等方面理论,分析了降雨对遗址的破坏形式及影响因素。结果表明,降雨对遗址的破坏形式可分为直接破坏和间接破坏两大类。其中,主要破坏形式为冲沟侵蚀、片流面蚀和雨蚀剥离。影响因素包括降雨特点、遗址形态、土的性质、植物生长状况和地幔层等,不同破坏形式的主要影响因素各有不同。本结果不仅丰富了降雨对土遗址破坏方面的研究,还为后续陕西榆阳区明长城保护加固措施的选择提供了依据。     

Managing a Monitor — the Case of HMVS Cerberus in Port Phillip Bay: Integration of Corrosion Measurements with Site Management Strategies

Abstract

The hull of the former HMVS Cerberus (1926) collapsed two metres during gales in December 1993, leaving the vessel half-submerged. Sunk as a breakwater in 1926, the vessel is one of the few remaining and accessible twin-turret Monitor-style warships from the 1870s. This paper presents the complex history of attempts to stabilize the site and to preserve the wreck. A series of in situ corrosion studies of corrosion potentials, pH, and residual metal thickness have provided a special insight into the processes of decay and have paved the way for future site stabilization. Removal of the four 16-tonne 10 inch Armstrong rifled muzzle loading guns and their in situ treatment alongside the wreck have assisted in relieving some of the stress on the remaining structure. The paper reports on correlations between the corrosion rate and the formation of concretions and how to determine the end point of an in situ treatment for cannon.     

Drowned and deserted: a submerged prehistoric landscape in the Solent, England

A submerged landscape containing worked flint tools has been found at—11m OD in the western Solent. This paper reviews coastal sites in northern Europe and suggests that many similar sites should exist around the coast of southern England; as a result of isostatic shifts and eustatic fluctuations many coastal sites of the Mesolithic will now be submerged. A need has been identified to locate, protect and record submerged sites before they are lost to erosion or development, for which outline proposals are suggested.     

Archaeological Survey of the Ex-USS <Emphasis Type="Italic">Independence</Emphasis> (CVL22)

In August 2016, a multidisciplinary team conducted the first archaeological survey of the deep-water (829 m) wreck of the ex-USS Independence (CVL22) using the remotely operated vehicles Argus and Hercules. The survey provided 34 h of direct observation with video and still camera documentation of the wreck, which the previous year had been initially identified with a limited three-dimensional sonar survey of the site. The 2016 assessment added considerably to an understanding of changes to Independence after its use as a target vessel for the 1946 atomic bomb tests at Bikini Atoll, as a radiological laboratory, training facility, and finally as a receptacle for “nuclear waste” prior to its scuttling off California in January 1951. The location and detailed examination of the wreck, along with additional archival research, offers a more nuanced definition of the carrier’s role within the context of the Cold War between the USSR, its adversaries and the race to establish nuclear supremacy, as well as site formation processes and ongoing biological colonization of the wreck site. As well, no evidence of residual radiological contamination was noted during the mission.     

Site Charting and Environmental Studies of the Monitor Wreck

Abstract

Marine geological and geophysical techniques have been applied to studies of the Monitor wreck to chart the fragments of the wreck and to determine the corrosion state of the remaining iron and the state of the geological and oceanographic environment in the immediate area of the wreck. Methods included magnetic surveying of the wreck site, computer calculations of the magnetization of the Monitor iron, and comparisons with magnetic measurements on iron artifacts from the wreck. Piston coring of the strata immediately beneath the wreck and near-bottom current measurements revealed evidence on the sedimentation rates and sediment transport at the site; these data confirmed interpretations made from high-resolution subbottom reflection profiles across the site.     

Microbiology of Concretions, Sediments and Mechanisms Influencing the Preservation of Submerged Archaeological Artifacts

Research conducted at deep-ocean ship wreck sites in the North Atlantic Ocean, the Mediterranean Sea and in the Gulf of Mexico have revealed that microorganisms play a significant role in both the preservation and loss of submerged artifacts. Research to be reported concentrates on the influence of microbiologically induced concretions on the survival of maritime artifacts. Rusticles, a common form of concretion, have been found to provide valuable information to archeology (Garzke et al. 1997, Proceedings of the Society of Naval Architects and Marine Engineers). The role of rusticles in the preservation of recalcitrant materials such as coal and glass fragments that become embedded within these growths, as well as forensic chemical analysis can be used to determine the nature of goods or munitions being carried by the ship at the time of its sinking, and will form examples.     

Mapping of the Buried Yarmouth Roads Wreck, Isle of Wight, UK, using a Chirp Sub-Bottom Profiler

Remains of the 16th-century Yarmouth Roads wreck, buried in sediments, were imaged using high-resolution geophysical techniques. The remains appear as strong reflectors underlain by an acoustic blanking zone, which was used to create maps of the wreck material. Close survey line-spacing allowed the construction of contour maps and hull sections, which revealed that the bow and stern sections are tilted to port at different angles, implying that they are detached. The seismic data have enhanced our understanding of the site beyond what was known from conventional archaeological investigations and confirms that this wreck was once a large carrack.
© 2007 The Authors     

Evaluation of Structure from Motion Software to Create 3D Models of Late Nineteenth Century Great Lakes Shipwrecks Using Archived Diver-Acquired Video Surveys

Here we demonstrate the ability to use archived video surveys to create photorealistic 3D models of submerged archeological sites. We created 3D models of two nineteenth century Great Lakes shipwrecks using diver-acquired video surveys and Structure from Motion (SfM) software. Models were georeferenced using archived hand survey data. Comparison of hand survey measurements and digital measurements made using the models demonstrate that spatial analysis produces results with reasonable accuracy when wreck maps are available. Error associated with digital measurements displayed an inverse relationship to object size. Measurement error ranged from a maximum of 18 % (on 0.37 m object) and a minimum of 0.56 % (on a 4.21 m object). Our results demonstrate SfM can generate models of large maritime archaeological sites that for research, education and outreach purposes. Where site maps are available, these 3D models can be georeferenced to allow additional spatial analysis long after on-site data collection.     

Holistic geoarchaeology in the Penobscot Valley,Maine, USA: context,scale, and interpretation

A holistic landscape approach to cultural resource analysis of a set of archaeological sites in the central Penobscot Valley led to inferences regarding the Holocene physical and biological environmental context. Targeted environmental studies include (1) examination of forest and wetland changes through time and (2) lake-level studies as a key to paleohydrology. These studies were combined with broad-scale geomorphic investigations and detailed stratigraphic analyses, and studies of archaeological sites and their artifact assemblages. Together, these studies provide a picture of dramatic changes to the physical and vegetational landscape. These included reestablishment of a major river following deglaciation, evolution of extensive lakes to uplands and peatlands, and a shifting mosaic of open and closed forest composed of a variety of hardwood and softwood species. Inferences based on buried soils exposed in archaeological excavations supported climatic interpretations based on vegetation and paleohydrology. As a result, this work allowed evaluation of (1) site formation and preservation processes and (2) occupational patterns. Site formation and preservation of Early Holocene sites can be linked to sedimentation by hydraulic damming upstream of rapids at the mouths of tributary streams. Shifting human land use reflected by changes in occupation patterns appears to correspond to changes in forest composition as well as wetland and stream evolution through time.     

ANALYSIS OF THE FATTY DEBRIS FROM THE WRECK OF A BASQUE WHALING SHIP AT RED BAY,LABRADOR

Analysis of fatty material from barrels in a submerged wreck of a whaler in Labrador water showed it to contain free fatty acids, including some higher fatty acid, consistent with whale oil and certainly of marine origin. Conversion to adipocere was extensive but not complete.     

The role of research and education in site management at the Lemba Experimental Village,Cyprus

Abstract

The project developed at the Lemba Experimental Village in Cyprus seeks to explain some aspects of the workings of archaeology through the medium of an ongoing and dynamic research project. The Lemba Experimental Village was established in 1988 with a view to understanding site formation processes through the construction of full-scale experimental buildings of the Chalcolithic period (3500–2800 BC). Experiments have been carried out with mud construction, lime plaster making and building construction. Monitoring and recording of construction and erosion processes provides a long-term history of events on the site which can be related to the deposits and features encountered when excavation is undertaken. Comparative information has been obtained from the structural analysis and excavation of buildings abandoned 25–30 years ago in the village of Souskiou, where similar deposits are encountered. The results of the work at Lemba and Souskiou are used as a comparative database for understanding deposits on prehistoric archaeological sites. The juxtaposition of the experimental building constructions with completed excavations at Lemba has led to the emergence of a policy of site presentation in which the methods of a particular form of archaeological research – experimental archaeology – constitute the main focus of interest on the site. This has been encouraged in the development of the site as a visitor centre, with an annually changing programme of new buildings being constructed and older ones being destroyed.     

Shipwreck Evidence from Kilwa,Tanzania

This article reports on the artefacts and environment of marine ballast and pottery sites identified through inter‐tidal and underwater survey around Kilwa, Tanzania, one of the most important medieval sultanates along the east African coast. An inter‐tidal site on the limestone fringing reef on the approaches to Kilwa Kisiwani Harbour and an underwater site within the harbour have been dated from associated pottery to c.8th–10th century and the 13th–16th century respectively. The presence of exotic basalt ballast is discussed as an indicator of wreck‐sites.     

Urban geoarchaeology and environmental history at the Lost City of the Pyramids,Giza: synthesis and review

Sediment accretion in ancient urban sites and tells records a combination of cultural and geomorphic processes. Urban geoarchaeology is focused on site accumulation, collapse, weathering and erosion, as constrained by architectural plans and structures. These may document settlement growth and decay, as well as environmental history, posing a multidisciplinary challenge of interactive and fluctuating processes.     

Discard behavior on domestic historic sites: Evaluation of contexts for the interpretation of household consumption patterns

Consumer behavior has become an important topic in historical archaeology, and patterns of domestic acquisition, use, and discard are often directly expressed in the archaeological record. Consumption patterns are influenced by factors such as household morphology, life cycle, ethnicity, and socioeconomic status, therefore analysis of domestic site formation processes should take these factors into account. The formation processes exhibited on historic domestic sites may be quite complex, but there is a broad range of analytical methods available for examination of these processes.     

Under the Boards: Archaeological Site Formation Processes at the Commissariat Store, Brisbane

The study of archaeological site formation processes, although routinely undertaken for prehistoric sites, is only carried out in historical archaeology in a limited way. Understanding the processes which formed the archaeological record of a site is an important first step towards developing justifiable inferences about past behavior and past societies regardless of the age of the site. This paper identifies and examines the cultural and non-cultural processes that formed the archaeological record at the Commissariat Store, Brisbane. The history of the site, from its construction in 1829 as part of the Moreton Bay penal settlement to the present, is examined and the expected impacts and processes on the archaeological record are identified. Archaeological evidence from the salvage excavation of the site undertaken in 1978 and 1979 is analyzed to identify the cultural and non-cultural site formation processes. This study identifies the presence of cultural formation processes including discard, loss, abandonment and re-use from an examination of the historical and archaeological evidence. Non-cultural formation processes at work in the site include faunalturbation, floralturbation, flooding, and aquaturbation.