Depositional Context Research Articles

Lithofacies and Microfacies Study of ATE Maastrichtian Reefal Limestones and Comparison with the Aqra Formation, Northeast and Northern Kurdistan Region-Iraq

The Maastrichtian reefal limestone, which developed variably across the northern and northeastern Kurdistan Region of Iraq, includes the Aqra Formation, which formed extensive platforms in the Aqra-Barzan area throughout the Maastrichtian period. Additionally, bars and lenses of reefal limestone in the upper part of the Tanjero Formation created longitudinal submarine ridges in the Arabian-Eurasian Foreland basin. This study selected three sections: the Aqra Formation in the type section and study the reefal limestone lenses in the Upper part of the Tanjero Formation at the Kunamasi and limestone bars in the Balakaity. Focusing on lithofacies and microfacies to determine if these reefal limestones are part of the Aqra Formation. The type section of the Aqra Formation, located in the Aqra area, features significant reefal limestone approximately 700 meters thick, including rudists with bitumen and some dolomite content. This formation is widely deposited in the Aqra and Barzan areas, overlying the Bekhme platform stratigraphically, and extends geographically from Bujel to Chia Gara anticlines. Four submicrofacies identified in this reefal limestone are Miliolids packstone, Rudists floatstone, Peloidal grainstone, and Bioclastic foraminifera grainstone. In the Kunamasi area, the reefal limestone appears as thick deposits associated with marl and sandy claystone beds, approximately 30 meters thick, and situated above the flysch Tanjero Formation. Key submicrofacies here include Omphalocyclus packstone, Rudists floatstone, and Echinoids grainstone. At the Balakaity section, the reefal limestone consists of a single, thick body exceeding 50 meters in thickness, directly overlying the Tanjero Formation and restricted to the Dar-Alsalam area. The submicrofacies in this section include Foraminifera packstone, Omphalocyclus packstone, and Rudists floatstone. Overall, the microfacies interpretation is the Aqra Formation is deposited as a large platform in inner and middle ramp settings. Conversely, the reefal limestone in the Balakaity and Kunamasi areas appears to be part of submerging islands within the flysch marine environment of the Tanjero Formation during the active Arabia-Eurasian Subduction. Based on depositional context and microfacies analysis can be concluded the reefal limestone in these areas is more likely associated with the Tanjero Formation rather than the Aqra Formation.

Red Deer Antler Artefacts from Gordineşti II- ”Stînca goală” and Vynnyky-”Zhupan”: Shape-and-Trace Formation Processes in Natural, Functional and Depositional Contexts

The paper scrutinizes the red deer hard tissues from the contexts attributed to the Trypillia Culture’s final phases. Having once been reported elsewhere, the objects under study are this time conceptualized in terms of shape-and trace formation processes, with an eye to incorporating them into research advances under the topic of the late Trypillia transformation, including typological affiliation, radiocarbon dating, archaeoecology, subsistence studies, etc. Particular attention is paid to artefacts that lack the overwhelming power of the tiniest wear marks, but do display extensive topographic features of manufacture and use. The formalized shape-and-trace aspects for the antler artefacts are proposed, which are considered to be suitable rather for a morphological than for a morphographicsystematization of a prehistoric antler assemblage. An interpretative application of the shape-and-trace approach for the sake of clarification of both past currents in morphogenesis of artefacts and praxis of their use is only possible in a systemic context of knowledge about habitats and lifestyles of the past.

Macrolithic retouched blades from Kałdus and Stare Marzy: foreign technology and new ideology in the lithic traditions of the TRB communities in the Lower Vistula region

At the turn of the 20th and 21st century, over a dozen macrolithic retouched blades or their fragments were obtained from archaeological sites at Kałdus and Stare Marzy, located in the Lower Vistula region in northern Poland. The context of deposition links the blades to the settlements of the younger Funnel Beaker culture (3650/3500–3300/3100 BC). This article presents and discusses the results of morphological, technological, and raw material investigations of the macrolithic retouched blades or their fragments from Kałdus and Stare Marzy and relates them to the patterns of use and cultural significance of the macrolithic industry in the local TRB communities. The obtained results show that the retouched blades were made of high-quality flint materials sourced from the Polish and Ukrainian Uplands, namely Świeciechów, Volhynian and Jurassic flints. The results, furthermore, indicate that production technology of macrolithic retouched blades is very specific and, what is more important, it is not rooted in the lithic traditions of the region. Archaeological evidence from this study suggests exceptional patterns of use of macrolithic retouched blades in the Lower Vistula region and their perception by local TRB people, which can be traced to the Eneolithic milieu located southeast of the Polish Lowlands.

The Mundeck Salt Unit: A Review of Aptian Depositional Context and Hydrocarbon Potential in the Kribi-Campo Sub-Basin (South Cameroon Atlantic Basin)

The Kribi-Campo sub-basin, located in the Gulf of Guinea, constitutes the southeastern segment of the Cameroon Atlantic Margin. Drilling in the Aptian salt unit revealed a sparse hydrocarbon presence, contrasting with modest finds in its counterparts like the Ezanga Salt in Gabon and the Rio Muni Salt in Equatorial Guinea. This discrepancy prompted a reassessment of the depositional context and hydrocarbon potential of the Mundeck salt unit. By integrating 2D seismic reflection and borehole data analysis, this study established the structural and stratigraphic framework of the area, emphasizing the salt unit’s significance. Borehole data indicate a localized salt unit offshore Kribi, with seismic reflection data revealing distinct forms of diapir and pillow. This salt unit displays a substantial lateral extent with thicknesses ranging from 4000 m to 6000 m. The depositional context is linked to the following two major geological events: a significant sea-level drop due to margin uplift during the Aptian and thermodynamic processes driven by transfer faults related to mid-oceanic ridge formation. These events were crucial in forming and evolving the Mundeck Salt. Regarding hydrocarbon prospects, this study identifies the unit as being associated with potential petroleum plays, supported by direct hydrocarbon indicators and fault-related structures. The findings suggest that untapped hydrocarbon resources may still exist, underscoring the need for further exploration and analysis.

Deciphering Permian wetland deposits of the Parnaíba Basin through an integrated study of lithofacies and palynofacies in Western Gondwana

During the Permian, the northwestern portion of the supercontinent Gondwana experienced significant climate changes, among which the increasing aridity in the Parnaíba Basin, located between Brazil's northern and northeastern regions. The marine influence associated with the Panthalassa Ocean, evident in the Silurian and Devonian deposits, was progressively attenuated in the late Carboniferous, culminating in extensive continental deposits during the Permian and the Early Triassic in this region. In this paper, we present the first palynofacies analysis of the Permian Pedra de Fogo Formation, conducted concurrently with the description and association of sedimentary facies from outcrops located in the state of Maranhão, southwest of the Parnaíba Basin. A total of 15 m of sedimentary succession was described, and 28 samples were selected for palynofacies analysis. As a result, we identified six sedimentary facies, which were grouped into two distinct facies associations: Fa1 – Central Lake and Fa2 – Playa Lake. The palynofacies analysis considered the sedimentary organic matter, classifying it into amorphous organic matter, phytoclasts (subdivided into eight subgroups), and palynomorphs (with six subgroups). Integrating the results enabled an understanding of the depositional context, which is closely related to water dynamics and climate seasonality. The shallow lake system interpreted during the wet phases recorded interruptions in the normal sedimentation of the central lake due to turbidite deposits associated with ephemeral rivers. Conversely, during dry phases, salt precipitation occurred with subsequent substitution and aerial exposure of the surface when the water balance was negative. Eodiagenetic events were inferred and are considered throughout the article. The alternation of the hydrological regime allowed the deposition in proximal, transitional, and distal environments, creating a distinctive mosaic of wetland landscapes. The data presented indicate humid conditions within a context of increasing aridity in the studied location, particularly in the upper part of the Pedra de Fogo Formation.

High levels of consanguinity in a child from Paquimé, Chihuahua, Mexico.

This study reports results from the ancient DNA analysis of a unique child burial at Paquimé, northern Chihuahua, Mexico. Located between Mesoamerican and Ancestral Puebloan groups, Paquimé (also known as Casas Grandes) was a vibrant multicultural centre during the 13th-14th centuries AD. Archaeologists have long debated Paquimé's social organization. Our analysis of Burial 23-8 has revealed that this child, placed under the centre post of an important room, had parents who were close genetic relatives. We argue that this child's consanguinity and special depositional context resulted from an elite family's practice of aggrandizing social status.

Predicting ecology and hearing sensitivities in Parapontoporia-An extinct long-snouted dolphin.

Analyses of the cetacean (whale and dolphin) inner ear provide glimpses into the ecology and evolution of extinct and extant groups. The paleoecology of the long-snouted odontocete (toothed whale) group, Parapontoporia, is primarily marine with its depositional context also suggesting freshwater tolerance. As an extinct relative of the exclusively riverine Lipotes vexillifer, Parapontoporia provides insight into a transition from marine to freshwater environments. High-resolution X-ray CT scans (~3 microns or less) of three individual specimens from two species, P. sternbergi and P. pacifica, were acquired. Digital endocasts of the inner ear labyrinths were extracted non-destructively. Nine measurements of the inner ear were compared with an existing dataset covering 125 terrestrial and aquatic artiodactyls. These measurements were then subjected to a principal component analysis to interpret hearing sensitivities among other artiodactyls. Based on our analyses, Parapontoporia was likely to have been able to hear within narrow-band high frequency (NBHF) ranges. This finding indicates another convergence of NBHF-style hearing, or, more intriguingly, suggests that it may be an ancestral characteristic present among the longirostrine dolphins that dominated in the Miocene prior to the evolution of more modern lineages.

Using quartz OSL signals from SAR cycles for sediment provenance studies

Quartz optically stimulated luminescence (OSL) sensitivity is varied and related to Earth surface processes and, thus, it has been shown to be a useful tool for appraising sediment recycling and provenance investigations. These investigations are mainly based on OSL data purposely measured for sensitivity calculations. However, it has been recently shown that the relative sensitivity of the quartz OSL fast component (%BOSLF) from the first test dose (Tn) signal from an OSL dating measurement using the Single Aliquot Regenerative-dose (SAR) protocol can be used to discriminate sediment sources. Here, we investigate the possibility of characterizing %BOSLF for provenance purposes using not only Tn signals but all other OSL signals obtained over SAR protocol cycles from OSL dating measurements. We address the %BOSLF behaviour over SAR cycles (if conservative or not), the %BOSLF dependency on dose-size, differences between %BOSLF values given by natural/regenerative and test dose signals, and %BOSLF application for provenance studies. Quartz sand grains data from twenty Late Quaternary sediment samples, representing orogenic and cratonic sources and diverse depositional contexts from South America, Africa, and Asia, are included in the analysis. All calculations were performed using data that have been previously obtained for equivalent dose estimation. The key finding is that the averaged %BOSLF of all SAR signals was representative of the samples' characteristic sensitivity and could satisfactorily discriminate samples from known sources, mainly in the case of high-sensitivity samples. We could distinguish sediment source areas by averaging the %BOSLF of OSL signals from SAR natural/regenerative and test doses together. Likewise, laboratories worldwide could produce regional/global sediment provenance fingerprinting reference data using their dating measurements accumulated throughout the last decade.

Marine bryozoan colonization of terrestrial biomineralized tissues: Taphonomic insights and forensic implications

AbstractThe taphonomy and diagenesis of bone and teeth recovered from any environments provide crucial information for forensic sciences and investigations. This leads to the estimation of the postmortem interval (PMI) and the postmortem submersion interval (PMSI) of the organism/s. Aquatic taxa can induce macroscopic and microscopic alterations in biomineralized tissues (e.g., grooves) or can colonize them by attachment (e.g., Bryozoa). Bryozoa are tiny invertebrates that form colonies in freshwater and saltwater. They can survive for years as suspension feeders in all climates. Most marine Bryozoa species have a biomineralized exoskeleton that can be preserved after their death. This research analyzes eight fragments of archeological elephant ivory with a known PMSI of 314 years, which were inhabited by three distinct bryozoan colonies. The variations in the preservation of the bryozoan exoskeletons and the overgrowth of different marine taxa reveal that one colony (lichenoporid cyclostomatid) was alive at the time of the ivory collection from the submerged archeological site while the two other colonies (cheilostomatid) had previously died at different times. The primary objective of this observation is to contribute to the understanding of the taphonomy of terrestrial mammalian biomineralized tissues recovered in marine environments. Additionally, the study discusses the potential forensic implications of this association, such as the evidence of marine submersion and the PMSI. A secondary objective is to present the Bryozoa colonies within a distinctive depositional context, considering that many bryozoan species of the Western Australian coast remain undescribed. The complexity of the Bryozoa ecobiology is also highlighted, with the need of further research (e.g., minimum time for colonization). Finally, this study highlights the urgency of multidisciplinary collaboration to advance aquatic forensic capabilities.

Dog Consumption at Tell Zirāʿa: Is It a “Cultural Marker” for the “Sea Peoples”?

It has been argued that the increase in the consumption of dogs in the southern Levant during the Iron Age was due to the advent of the Philistines/“Sea Peoples” into the region. In this study, we test this proposal through the presentation of new information on dog consumption and its depositional context in Bronze and Iron Age strata from the archaeological site of Tell Zirāʿa (Jordan), and we compare the results to other sites in the region. Our study does not support that such behaviour is a signal of ethnic identity.

Technological and Protein Residue Analysis on Ancient Stemmed Projectile Points of the Southern Andes Highlands

ABSTRACT We present the results of technological and protein residue analyses of the lithic assemblages recovered at the Pedernales-38 site (26.5°S; 69°W), located in the highlands of the southern Andes (3380 masl). Based on a reconstruction of the operational chains and the differential representation of their phases, we suggest that the final production, use, maintenance, and discard of large stemmed projectile points occurred at the site. Of the assemblage studied, nine (9) projectile points and one end-scraper were subjected to residue analysis using cross-over immunoelectrophoresis (CIEP). Four positive reactions to antisera of human, camelid (guanaco or vicuña) and canid (Andean fox) were recorded. The results are discussed based on the depositional context and the structure of the archeological record. We propose that Pedernales projectile points were mainly used in hunting weapons to capture wild camelids during the seasonal occupation of the Andes highlands.

Sedimentary and stratigraphic architecture in the geoarchaeological context of Late-Holocene deposits in the eastern coastal plain of Belgium: Zwin region – Hoeke

A sedimentary investigation was carried out into the rise and fall of mediaeval Bruges’ maritime access. Because the mediaeval metropolis had no direct connection with the North Sea, its maritime connectivity during the High- and Late-Middle Ages depended on a tidal channel, known as the ‘Zwin’. In order to reconstruct the mediaeval physical environmental situation correctly, the entire Holocene sedimentary record was studied through undisturbed mechanically-drilled cores and electrical cone penetration tests (CPT-e). A detailed sedimentary analysis was complemented with radiocarbon dating and datable archaeological finds to resolve a timeframe for the sedimentary evolution. Tidal channel systems with diverse morphologic and sedimentologic characteristics prevail and cover a period from at least the Roman period till the Late-Middle Ages. The presence of a single peat layer directly on top of the Pleistocene substrate and the stratigraphic position of the tidal channel deposits relative to this peat layer, proves that no seawater entered this part of the Belgian coastal plain before the Late-Holocene. The tidal channel system that was active during the heydays of Bruges (the Zwin) was the last natural one. It silted up due to a further reduction of the accommodation space as a consequence of new embankments, possibly expedited by storms.

Preservation of bone organic fraction is not predictive of the preservation of bone inorganic fraction when assessing stable isotope analysis sample quality control measures

Stable isotope analysis of carbon (C), nitrogen (N), hydrogen (H), and oxygen (O) of archaeological bone has become an increasingly common research method for interpreting human behavior in the past. However, diagenesis of skeletal material can invalidate stable isotope ratios, thereby compromising interpretations. We examine patterns of bone diagenesis using infrared spectroscopy of bone bioapatite samples in relation to indicators of organic preservation quality indicators. We assess crystallinity, an indicator of bioapatite preservation, using the infrared splitting factor (IR-SF) and carbonate content (carbonate to phosphate ratio, C/P) calculated from infrared spectra. We then test the assumption that if the organic fraction of bone is preserved, the mineral fraction will also be unaffected by postmortem chemical alteration. We analyzed 454 bone bioapatite and extracted bone organic sample pairs from modern, historic, and prehistoric humans. Consistent with previous studies, we observed a strong, statistically significant negative linear relationship between IR-SF and C/P (r = −0.855, p < 0.001). Modern bone bioapatite samples unaltered by diagenesis have low IR-SF and high C/P values. There was no significant association between the collagen yield or atomic C:N ratio and IR-SF or C/P values. The range of variation in IR-SF and C/P values for samples with organic yields between 0 and >20 percent spanned the range of modern bone bioapatite unaltered by diagenesis as well as bone bioapatite significantly affected by diagenesis. The lack of predictive patterning between bone inorganic and organic diagenesis suggests that the depositional context and site formation history play critical and independent roles in the organic and mineral fraction of bone. Thus, the preservation of the organic fraction of bone is not predictive of the preservation of the inorganic fraction (e.g., bioapatite).

CHRONOLOGICAL MODELING ON A CALIBRATION PLATEAU: IMPLICATIONS FOR THE EMERGENCE OF AGRICULTURE IN THE DUTCH WETLANDS

ABSTRACTShort-duration archeological sites situated entirely within plateaus in the radiocarbon calibration curve pose unique challenges for our understanding of past processes at regional and global scales. This paper aims to overcome these limitations by leveraging the specific characteristics of two depositional contexts, the Early Neolithic Swifterbant Culture sites S3 and S4, located in the Dutch wetlands. These sites are of exceptional significance as they provide the earliest conclusive evidence of crop cultivation and animal husbandry outside the expansion of Linearbandkeramik (LBK) farmers in north-western Europe. Here, we present a customized approach that combines radiocarbon dating and Bayesian modeling, predicated on vertical sequences of short-lived plant remains. Our innovative approach enables us to determine, at a fine scale, the temporal position and duration of the prominent archeological contexts at S3 and S4, and explore the chronological relationship between the two sites. Through our analysis, we propose a new chronology for the onset of Neolithization in the Dutch wetlands.

THE SIZE INHERITED AGE EFFECT ON RADIOCARBON DATES OF ALLUVIAL DEPOSITS: REDATING CHARCOAL FRAGMENTS IN A SAND-BED STREAM, MACDONALD RIVER, NSW, AUSTRALIA

ABSTRACT Radiocarbon dates on charred plant remains are often used to define the chronology of archives such as lake cores and fluvial sequences. However, charcoal is often older than its depositional context because old-wood can be burnt and a range of transport and storage stages exist between the woodland and stream or lake bed (“inherited age”). In 1978, Blong and Gillespie dated four size fractions of charcoal found floating or saltating in the Macdonald River, Australia. They found larger fragments gave younger age estimates, raising the possibility that taphonomic modifications could help identify the youngest fragments. In 1978 each date required 1000s charcoal fragments. This study returns to a sample from the Macdonald River to date individual charcoal fragments and finds the inherited age may be more than 1700 years (mode 250 years) older than the collection date. Taphonomic factors, e.g., size, shape or fungal infestation cannot identify the youngest fragments. Only two fragments on short-lived materials correctly estimated the date of collection. In SE Australia, this study suggests that wood charcoal will overestimate the age of deposition, taphonomic modifications cannot be used to identify which are youngest, and multiple short-lived materials are required to accurately estimate the deposition age.

Revisiting site history and regional interaction at the Dia settlement mound complex, Mali

ABSTRACT Previously unpublished results of test excavations in 1986–1987 at Dia, an extensive occupation mound complex on the western margins of the Inland Niger Delta in Mali, have been augmented by a series of new AMS dates. This article explores how the excavation and radiocarbon data together provide new insights into occupation sequences and site formation processes. It presents details on the depositional contexts, chronology and associated material culture at each of the 1986–1987 excavation units. Using these data, we examine the role of post-depositional disturbance, secondary deposition and re-use of earlier cultural deposits in interpreting site formation processes at the Dia settlement mounds. In addition, we emphasise the important role that studies of well-contextualised pottery from excavation can play in evaluating regional interactions through comparisons with other documented sequences in neighbouring areas, including Jenne-jeno and the Méma. This focus on site formation and regional interaction enables new interpretations that also interrogate and expand the results of the larger-scale excavations at Dia by an international team between 1998 and 2002.

Reevaluating the process regime in the Sego Sandstone: Sedimentological and ichnological evidence for an underemphasised fluvial signature

AbstractRocks of coastal to shallow‐marine origin are challenging to interpret owing to the complex interplay of various depositional processes. This study reevaluates the relative roles of fluvial, tidal and wave processes in the Upper Cretaceous Sego Sandstone (and subordinately in the underlying Buck Tongue) of the Book Cliffs, USA, a well‐studied ancient coastal to shallow‐marine succession. Detailed sedimentological and ichnological analyses were used to interpret a previously underemphasised riverine signature, consisting of centimetre‐ to decimetre‐thick alternations of sandstone and heterolithic beds inferred to represent flood–interflood periods of variable river discharge. Recognition of a widespread fluvial‐dominated signature across the studied units better agrees with other sedimentological and regional observations in the study area, such as high sandstone–mudstone ratios, largely unidirectional and seaward‐oriented palaeocurrents, and modelled weak tidal conditions in the basin. When considering all of the sedimentological, ichnological and stratigraphic observations together with its regional depositional context, the Sego Sandstone/Buck Tongue system is better explained using a mixed‐energy but fluvial‐dominated deltaic model. This highlights an historical over‐interpretation of tidal processes and subordinate wave processes in the Sego Sandstone and likely in similar units. The widely used approach that emphasises only certain sedimentary features in discerning the process regime from analysis of rocks of inferred coastal to shallow‐marine origin is unrefined and may therefore underrepresent the actual complexity of these systems.

A Tauriscan Lt D obol from Lobor hillfort (Hrvatsko Zagorje, Croatia)

&#x0D; &#x0D; &#x0D; A small silver coin complementary to the Augentyp-Stamm Tauriscan obols was found in controlled archaeological excavations at the Lobor hillfort. The hillfort was fortified in the late La Tène period (Lt D), which is also the most likely depositional context of the coin, since the site was clearly not occupied during the early imperial age. It can be assumed that the coin was produced in the earlier part of late La Tène (Lt D1), in accordance with the presently accepted chronology of Tauriscan coins. Similar obols were found at comparable hillfort sites in the Tauriscan area, but, due to their small number and lack of secure stratigraphic contextualization, this phenomenon is not easily explained in terms of commercial exchange.&#x0D; &#x0D; &#x0D;

Heirlooms Under-‘Cover’: Identifying Curated Swords and Scabbards Deposited in Early Medieval Burials

EARLY MEDIEVAL SWORDS have been a popular subject of historic and archaeological study in recent years. Swords have been found within the wealthiest early Anglo-Saxon furnished burials (the 5th–7th centuries ad) and have been recorded as highly decorated objects representing social status. From both archaeological and literary evidence, early medieval swords have been considered as likely ‘heirloom status objects’, curated and inherited over multiple generations. However, until recently there has been no direct study of the curation of swords. This is due to the problematic chronological nature of sword components, and because almost all are from burial contexts of the early Anglo-Saxon period. This study analysed graves containing swords from Kentish cemeteries of the 5th–7th centuries AD, and identified two examples of potential curation strategies through sword scabbard pieces chronologically older than the depositional context or individual within the grave. The evidence supports the belief that swords were recognisable heirlooms within early medieval communities, displaying the biography of the weapon, owner, and family. The recognition of an heirloom sword within a burial tableau would have been a socially noticeable action, affecting the collective memory of the mourners gathered at the funeral during a time of social and political stratification.

Basin and depositional control on the initiation and development of fluid-escape pipes in the Canterbury Basin, New Zealand

The influence of basin and depositional context on the formation and growth of fluid escape pipes in sedimentary basins is not fully understood. While seismic reflection data is commonly used to study these structures, direct observation and sampling are scarce. In this study, we investigate the evolution of hundreds of meter-tall fluid escape pipes (100–800 m) in the Canterbury Basin, New Zealand, using open source seismic and borehole data. Our analysis includes seismic interpretation of 19 unconformities within the Neogene-Quaternary successions, characterization of pipes and fluid-related anomalies in the subsurface, modeling of the shale volume (Vsh), lithology characterization, 3D static modeling, and seismic inversion. We identify thirty-one vertical to sub-vertical pipes with three parts consisting of top, main conduit/stem, and root zone on seismic profiles. Our results suggest that lithology plays a crucial role in the initiation and modulation of pipe structures in the Canterbury Basin, with pipes mostly formed post Tarantian (0.113 Ma) and truncated at the U19 unconformity. Furthermore, vertical fluid migration from overpressured units, such as the tops of contourite mounds, was observed in the pipes. Our findings provide new insights into the subsurface fluid flow and sedimentary architecture of the Canterbury Basin and have wider implications for other passive continental margins with similar characteristics.