The origin of overpressure in 'old' sedimentary basins: an example from the Cooper Basin, Australia

Overpressure in ‘old’ sedimentary basins that have not undergone rapid, recent sedimentation cannot be easily explained using traditional burial‐driven mechanisms. The last significant burial event in the Cooper Basin, Australia, was the Late Cretaceous deposition of the Winton Formation (98.5–90 Ma). Maximum temperature in the basin was attained during the Late Cretaceous, with cooling beginning prior to 75 Ma. Hence, overpressure related to rapid burial or palaeomaximum temperatures (e.g. hydrocarbon generation) must have developed prior to 75 Ma. Retaining overpressure for 75 Ma in ‘old’ basins such as the Cooper Basin requires extremely low seal permeabilities. An alternative explanation is that overpressure in the Cooper Basin has been generated because of an increase in mean stress associated with an increase in horizontal compressive stress since Late Cretaceous times. Structural observations and contemporary stress data indicate that there has been an increase in mean stress of approximately 50 MPa between Late Cretaceous times to that presently measured at 3780 m. The largest measured overpressure in the Cooper Basin is 14.5 MPa at 3780 m in the Kirby 1 well. Hence, disequilibrium compaction driven by increasing mean stress can explain the magnitude of the observed overpressure in the Cooper Basin. Increases in mean stress (tectonic loading) may be a feasible mechanism for overpressure generation in other ‘old’ basins that have undergone a recent increase in horizontal stress (e.g. Anadarko Basin).     

Agriculture and community in Chaco Canyon: Revisiting Pueblo Alto

The Bonito Phase (ca. AD 860–1140) in Chaco Canyon is widely recognized as one of the primary sources of information about emergent social complexity in prehispanic North America. Large masonry buildings called “great houses,” such as Pueblo Bonito, are iconic symbols of the rapid rise of a powerful society based on the ability to harness labor to prolonged construction projects. It is clear that the political forces at work during the Bonito Phase had an agricultural foundation, presumably in the financing of construction through food surpluses, but the actual nature of farming in Chaco is surprisingly opaque to archaeologists. Indeed, many researchers have concluded that farming in Chaco Canyon was too constrained by poor soils to have supported the dynamic developments associated with the massive stone structures and extensive trade systems of the Bonito Phase. The popular perspective that Chaco was mysterious or enigmatic is largely a response to this view of the canyon as agriculturally marginal. In this study we argue that a predictive model of potential agricultural productivity that includes other portions of the canyon besides the floodplain indicates that Chaco was not marginal for farming. The results of this analysis suggest that great house communities may have been sited to control local production zones and that some great houses may have been linked to others in order to manage multiple agricultural areas.     

Mapping ancient chinampa landscapes in the Basin of Mexico: a remote sensing and GIS approach

This paper uses remote sensing data to document a raised field, chinampa system adjacent to the Postclassic kingdom of Xaltocan in the northern Basin of Mexico. Various forms of landscape information; historic records and maps as well as remote sensing; are considered to understand the chinampa system. The remote sensing data examined include 1950s aerial photographs, Landsat 7 data, and Quickbird VHR, multi-spectral imagery. This article evaluates the utility of each of these forms of data to identify buried chinampa features and integrates them in a GIS to produce a map of Xaltocan's chinampa landscape. Canals of various sizes and hydrological positions comprised the chinampas and integrated the system together. Occupying at least 1500–2000 ha, Xaltocan's chinampa system represents the largest pre-Aztec, chinampa system in the Basin of Mexico.     

Patterning in procurement of obsidian in Chaco Canyon and in Chaco-era communities in New Mexico as revealed by X-ray fluorescence

X-ray fluorescence analysis of obsidian artifacts from sites located in Chaco Canyon and from three Chaco-era communities in New Mexico permits determination of their geological origin. These source data are used to describe patterning in obsidian procurement in sites located in Chaco Canyon dating from A.D. 500–1150, and in a three non-Canyon communities occupied during the period of Chaco Canyon's regional prominence (ca. A.D. 875–1150). These data demonstrate that the most proximate sources generally dominate the sourced obsidian assemblages from sites of all periods, but also suggest differences in procurement patterning both over time and across space. Within Chaco Canyon, there is a notable shift from Mount Taylor obsidian to use of Jemez Mountains sources over time. These data also suggest that earlier analyses of obsidian from sites in Chaco Canyon misidentified some obsidian artifact sources; these new data indicate the central areas of disagreement and provide a revision of procurement patterning. In the Chaco-era communities located outside Chaco Canyon, procurement patterning diverges. The Blue J community shows an increase in use of the nearby Mount Taylor source over time. Two communities located toward the southern extent of the Chaco great house distribution reveal a markedly distinct procurement pattern, obtaining nearly all of their obsidian from southern sources largely unrepresented at Chaco Canyon. Combined, these data provide new insights into raw material procurement and artifact production at sites in Chaco Canyon, and in communities occupied during the Chaco Phenomenon, the period of the Canyon's greatest regional influence.     

Development and application of methods used to source prehistoric Southwestern maize: a review

Archaeological cobs free of mineral contaminants should be used to source the soils in which they were grown. Mineral contaminants often contain much higher concentrations of metals than vegetal materials and can alter a cob’s apparent metal and heavy-isotope content. Cleaning a cob via immersion in an acid solution for more than a few minutes will result in the incongruent and sometimes complete leaching of metals, including strontium (Sr), from the cob. When using ⁸⁷Sr/⁸⁶Sr to determine the location of potential agriculture fields, it is best to either integrate several depth-integrated soil samples or to integrate several vegetation samples from individual fields. Biologically labile Sr in semi-arid Southwestern soils largely originates from eolian source or sources and usually is not derived from underlying bedrock. Existing Sr-isotope data indicate that archaeological cobs from Aztec Ruins came from either the Mesa Verde-McElmo Dome or Totah areas, that Pueblo Bonito and Chetro Ketl cobs, from Chaco Canyon that predate A.D. 1130, probably came from the Rio Chaco corridor, and that cobs from Chaco Canyon, that postdate A.D. 1130, probably came from either the Totah or Zuni areas.     

pXRF: a study of inter-instrument performance

Integrating portable X-ray fluorescence (pXRF) instrumentation into archaeological investigations has generated as much interest as skepticism because several characteristics of the technique limit analytical accuracy and precision. This paper seeks to explore inter-instrument performance in order to assess the potential pXRF instrumentation has in examining the elemental composition of lithic raw materials. Two pXRF instruments, Delta and Omega models both manufactured by Olympus Innov-X Systems, were utilized to obtain the trace element signatures of five fine-grained volcanic sources and four obsidian sources in the Great Basin. We compared the two portable instruments to a wavelength-dispersive instrument extensively calibrated with geologic standards and to a commercial benchtop energy-dispersive system. Our results suggest that the relationships between the data produced by these different instruments are complex, and as we look to the future of pXRF use in archaeological analysis we argue that that the same strict protocols applied in laboratory-based XRF analyses, involving instrument calibration, evaluation of inter-instrument performance, and comparison to accepted geologic standards, need to be applied in pXRF analysis.     

Revision of two phragmodontid species (Conodonta) from the Darriwilian (Ordovician) of the Canning Basin in Western Australia and phylogeny of the Cyrtoniodontidae

Zhen, Y.Y. 9 July 2019. Revision of two phragmodontid species (Conodonta) from the Darriwilian (Ordovician) of the Canning Basin in Western Australia and phylogeny of the Cyrtoniodontidae. Alcheringa XX, xxx–xxx. ISSN 0311-5518

Based on re-examination of the material used in the original study from the subsurface Goldwyer and Nita Formations (middle Darriwilian, Middle Ordovician) of the Canning Basin, Western Australia, two phragmodontid species (Phragmodus polystrophos Watson and Ph. spicatus Watson) are revised as having a septimembrate apparatus including geniculate (Ph. polystrophos) or nongeniculate (Ph. spicatus) M, triform alate Sa, modified tertiopedate (Ph. polystrophos) or tripennate (Ph. spicatus) Sb, modified bipennate Sc, modified quadriramate Sd, carminate Pa and pastinate Pb elements. Characterized by a carminate Pa element in their respective species apparatuses, these two species demonstrate a close phylogenetic relationship with Phragmodus cognitus Stauffer from the Late Ordovician (Sandbian) of North America. These distinctive shared characters have allowed their accommodation within a new genus, Protophragmodus gen. nov., which represents an evolutionary lineage separated from species of Phragmodus Branson & Mehl (sensu stricto). In addition, it is postulated that the Cyrtoniodontidae might have originated in the early–middle Darriwilian from ‘Plectodina’ in shallow-water settings, with Phragmodus (sensu stricto), the most derived part of the family, perhaps directly evolving from Protophragmodus gen. nov. in the late Darriwilian and then becoming cosmopolitan, deeper-water dwellers in the Late Ordovician.

Y.Y. Zhen [yong-yi.zhen@planning.nsw.gov.au], Geological Survey of New South Wales, W.B. Clarke Geoscience Centre, 947–953 Londonderry Road, Londonderry, NSW 2753, Australia.     

From Nihewan to Zhoukoudian: Cultural Evolution Pattern in the Paleolithic Age of Northern China

Nihewan and Zhoukoudian are important areas where early humans and cultures originated and reproduced in northern China and even East Asia. Geologically, both site groups belong to the Haihe River valley; chronologically, the Nihewan sites date to ca. 1.7 million years ago, and the Zhoukoudian sites date to ca. 0.5 million years ago; and culturally, both are dominated by the small-flake-tool culture. Thus, it is speculated that the early culture in the Zhoukoudian sites came from the migrants from the Nihewan Basin who facilitated cultural diffusion in the area; in turn, it also affected the culture in the Nihewan area during the subsequent development. This paper proposes the development path of the Paleolithic culture in northern China, that is, early humans in this region roughly experienced three stages of subsistence from lake-dependent to cave-dependent and then to river-dependent.     

Macro- and micro-archaeobotanical study of a vessel content from a Late Neolithic structured deposition from southeastern Hungary

A well-preserved assemblage of pottery and a broken stone artefact were excavated within a long house in the southern part of Tiszasziget, near the town of Szeged, Hungary. The settlement had been inhabited by the Late Neolithic Tisza culture around 5000–4500 BC. Based on the position of the finds it is suggested that the objects represent an ideologically-charged structured deposition. A piece of organic residue found in a mug (No. 18) with three-fold articulation has been subjected to macro- and microfloral analysis. After precise sampling of the residue, the standard methods to recover organic and inorganic plant remains were utilised. Based on the macrofloral and amino acid content analysis, it is suggested that the organic remains were pieces of fermented pastry made of cereal flour. The recovered silicified tissues and articulated phytoliths were subjected to morphometric measurements, which revealed that the food remain placed in the structured deposition was prepared of Triticum and – probably wild – Avena species. Starch granules of cereals were also detected, whilst the palynological evidence supports morphologies most likely to be related to the accompanying weed flora. The fortunate survival of the organic matter and the complex macro- and micro-archaeobotanical approach provided an unique opportunity to gain a better insight to the food preparation of Late Neolithic communities of the Carpathian Basin.     

Spatial–temporal distribution and geographic context of Neolithic cultural sites in the Hanjiang River Basin,Southern Shaanxi,China

Understanding how to live successfully within our environment is among the most pressing challenges facing contemporary society. This paper probes the problem based on comparative analysis and discusses the relationship between the spatial–temporal distribution of the Neolithic cultural sites and the geographic context in the Hanjiang River Basin in the south of Shaanxi Province, China. Archaeological studies have identified 175 Neolithic cultural sites in the study area, with a sequence of Laoguantai (¹⁴C age 8–7 ka BP), Yangshao (¹⁴C age 7–5 ka BP) and the late period of the Neolithic Age (¹⁴C age 5–4 ka BP). The total number of archaeological sites, the distribution area and the density all showed an early ascending and later descending trend, but the proportion of the number of archaeological sites in the study area to the corresponding value of the entire Shaanxi Province declined sharply. Spatially, these sites were concentrated on the terraces of the Hanjiang River and its main tributaries with an altitude of 400–800 m. Multiple data were integrated to clarify the critical effects of tectonic and geomorphologic conditions on the distribution of the Neolithic sites. Further comparisons revealed the correlation of Holocene climate change and environmental evolution with the Neolithic cultural succession in the study area that ameliorated conditions to generally promote the development of the primitive culture while degeneration coincided with the culture's transition or interruption. The discussion on the origin of the primitive culture and the temporal–spatial distribution corresponding to the regional culture differentiation sheds light on the complex and dynamic human–nature interaction system during the Neolithic Age, thus emphasising the wider field-based investigation and high-resolution reconstruction works of the palaeoclimate and palaeoenvironment in the future.