Engineering problems in ancient maya architecture: Past,present, and future

The ancient Maya faced a number of architectural engineering problems that they were unable to solve, except in the short term. Modern expectations for and use of Maya sites pose additional problems, and neither these nor the ancient ones have yet been fully resolved.     

Inverse methods for estimating primary input signals from time-averaged isotope profiles

Mammalian teeth are invaluable archives of ancient seasonality because they record along their growth axes an isotopic record of temporal change in environment, plant diet, and animal behavior. A major problem with the intra-tooth method is that intra-tooth isotope profiles can be extremely time-averaged compared to the actual pattern of isotopic variation experienced by the animal during tooth formation. This time-averaging is a result of the temporal and spatial characteristics of amelogenesis (tooth enamel formation), and also results from laboratory sampling. This paper develops and evaluates an inverse method for reconstructing original input signals from time-averaged intra-tooth isotope profiles. The method requires that the temporal and spatial patterns of amelogenesis are known for the specific tooth and uses a minimum length solution of the linear system Am = d, where d is the measured isotopic profile, A is a matrix describing temporal and spatial averaging during amelogenesis and sampling, and m is the input vector that is sought. Accuracy is dependent on several factors, including the total measurement error and the isotopic structure of the measured profile. The method is shown to accurately reconstruct known input signals for synthetic tooth enamel profiles and the known input signal for a rabbit that underwent controlled dietary changes. Application to carbon isotope profiles of modern hippopotamus canines reveals detailed dietary histories that are not apparent from the measured data alone. Inverse methods show promise as an effective means of dealing with the time-averaging problem in studies of intra-tooth isotopic variation.     

Maya utilization of karst groundwater resources

Much of the Maya civilization in pre-Columbian Meso-America was established on karst terrain that included parts of what are now Belize, Guatemala, northern Honduras and southern Mexico. By definition, little surface water exists in karst, so for the Maya to flourish on that terrain they had to effectively and efficiently utilize all their water resources. Access to groundwater was by means of springs and caves. Maya life, urban and rural, lay and elite, religious and secular was often a function of groundwater exploitation and surface water development. The Maya's use of groundwater was predominantly to supplement enhanced surface water supplies and was used more often in semiarid zones than in humid zones. The pattern of Maya settlements, especially in the semiarid zones, occurred in areas with greater access to the groundwater. Maya groundwater retrieval methods were primitive, inefficient, labor intensive, and uninnovative, as compared to their other technologic achievements. Groundwater contamination, from human effluent, could have resulted in widespread disease and contributed to the Maya's downfall.     

Platforms in the akalche at E1 Mirador,Peten, Guatemala and their implications

Late Preclassic Period platforms were surveyed and test-excavated in a seasonal swamp or akalche, at the large ancient lowland Maya site of El Mirador in Peten, Guatemala. Pedological, hydrological, and archaeological evidence suggest that the climatic and hydrological regimes were drier than they are today to permit habitation and warrant the investment in labor. Nevertheless, observations of present conditions, including the clayey soils, indicate that the akalche was almost as inhospitable in antiquity as it is today, that it had the same extremely poor agricultural potentials and that intensive wetland cultivation would have necessitated sizeable investments in dams to dampen the extreme seasonal fluctuations in water levels. Dams are not observed, and evidence is elicited to indicate that they would be readily observable today had they been emplaced here in antiquity. We offer evidence suggesting that these platforms had domestic functions, but we are forced to conclude that intensive wetland cultivation did not sustain them nor this large regional center as a whole. We argue, instead, that these habitations constitute evidence for population pressures on urban upland resources, especially building sites and perhaps agricultural land. Akalche households appear to have sustained themselves, at least in part, by foraging for animal and plant foods, cordage products, building materials, and firewood. The data are inadequate to decide if these structures housed full or part time specialists, or if they were self-sufficient in subsistence. © 1994 John Wiley & Sons, Inc.     

Soil properties and stable carbon isotope analysis of landscape features in the Petexbatún region of Guatemala

Soil properties and stable carbon isotope ratios contained in the soil organic matter (SOM) were used to investigate the change in vegetative history of land cleared anciently for maize (Zea mays L.) agriculture in the Petexbatún region of Guatemala. Maize and other C⁴ plants associated with land clearance leave a carbon isotopic signature in the SOM different from the C³ plants of native forest vegetation. Soil profiles were collected from various landscape features around the Classic Maya site of Aguateca: control locations (areas likely not used in ancient agriculture), defensible locations (areas near defensive walls), rejolladas (natural karst depressions), upland locations (well‐drained soils atop the Aguateca escarpment), and bajos (seasonal and perennial wetlands). The chemical and physical properties of the profiles were examined and the soils were taxonomically classified to the great group level. The changes in d¹³C with soil depth were determined and compared statistically. The ¹³C enrichment of the SOM in bajo and rejollada profiles were similar and were significantly (p < 0.05) greater than the control, defensible, and upland soils. This isotopic signature of sustained C⁴ vegetation was likely associated with forest clearance and ancient Maya agriculture. Both the bajo and rejollada landscape features appear to have been valuable agricultural resources for ancient Maya. © 2009 Wiley Periodicals, Inc.     

Petrological and geochemical relationships between pyroxene megacrysts and associated alkali-basalts from Massif Central (France)

Major, trace element, and REE analyses, as well as Sr isotopic ratios, have been obtained on twelve clinopyene megacrysts and phenocrysts and their alkali-basalt hosts from the French Massif Central. Equilibrium between crystals and host was examined based on petrographic and geochemical data.Two types of pyroxenes are recognized: the acmite-bearing clinopyroxenes, rich in incompatible elements and the salitic clinopyroxenes, poor in incompatible elements. ⁸⁷Sr/ ⁸⁶Sr isotopic data reveal no significant difference between clinopyroxenes and host lavas: they are in apparent isotopic equilibrium. The Sr isotopic ratios of the two types of pyroxenes are also quite similar. However pyroxene crystals from the first group are not in equilibrium with their host; they have crystallized at high-pressure from differentiated alkali-lavas and have been incorporated in a more primitive magma. Pyroxene crystals from the second group are in apparent equilibrium with their host lava; they have crystallized at various pressures. For the latter, distribution coefficients are proposed for compatible elements, trace elements and REE.     

Stable isotope differences among morphotypes of Neogloboquadrina pachyderma (Ehrenberg): implications for high-latitude palaeoceanographic studies

The stable isotopic composition of planktonic foraminifera plays a paramount role in interpretations of past oceanographic and environmental conditions; thus an accurate understanding of the factors which influence their isotopic composition is essential. In order to increase the palaeoceanographic utility of the high-latitude planktonic foraminifera Neogloboquadrina pachyderma , its shape and oxygen and carbon isotopic variability are quantitatively described in this study. Over 8200 specimens of N. pachyderma from 36 gravity and piston core tops from surface sediments of the North Atlantic and southern Indian Oceans were digitized and analysed via Fourier series in closed form. The morphological results are presented in detail elsewhere and are utilized in this study to select specimens for isotopic analyses. Significant isotopic differences exist between morphological variants of this important high-latitude speaes. Specimens become depleted in both oxygen and carbon isotopes as the test shape becomes more pentagonal and less quadrate. The isotopic differences cannot be attributed to test thickening nor to size or coiling direction. This observation has important implications in the use of this speaes as a tracer in high-latitude palaeoceanographic investigations. In particular, future isotopic investigations utilizing this species should analyse single forms to allow for clear interpretation of palaeoceanographic signals.     

The Yucatan,a Laurentian or Gondwanan fragment? Geophysical and palinspastic constraints

Current reconstructions suggest that the Yucatan block has Gondwanan provenance and orient the Yucatan E–W in the Ouachita embayment where it overlaps southern Laurentia and Florida. Alternatively, if the Yucatan is oriented NE–SW, it fits neatly into the Ouachita embayment with minimal overlap. Furthermore, many of the V-shaped, magnetic anomalies in the Yucatan that are discordant in the E–W reconstruction can be traced across the Yucatan–Laurentian boundary in the NE–SW reconstruction: (a) NW-trending anomalies continue into southern Laurentia where they are associated with Cambrian mafic rocks in the southern Oklahoma and Reelfoot rifts and (b) NE-trending anomalies in the eastern Yucatan are parallel to those over Grenvillian rocks in the western Appalachians. Furthermore, Silurian plutons in the Maya Mountains of Belize that have no counterpart in Texas may be correlated with the Concord–Salisbury plutons in Carolinia, a terrane of Gondwanan provenance in the southern Appalachians. Nd isotopic data from the Chicxulub ejecta in the northern Yucatan block are similar to those in the Llano Grenvillian rocks and differ from those in Oaxaquia. These correlations suggest that much of the Yucatan is of Laurentian provenance and implies that the Laurentia–Gondwana suture crosses the Yucatan west of the Maya Mountains. In this scenario, the Ouachita embayment results from the formation of the Gulf of Mexico during the breakup of Pangea, rather than the Cambrian removal of the Argentine Cuyania terrane. Cambrian (515 Ma) paleomagnetic and faunal data are consistent with Cuyania forming either east of the Yucatan or off eastern Laurentia.     

Study of melt and a clast of 546 Ma magmatic arc rocks in the 65 Ma Chicxulub bolide breccia,northern Maya block,Mexico: western limit of Ediacaran arc peripheral to northern Gondwana

The basement of the Maya block of eastern Mexico is generally covered by Mesozoic and Cenozoic platformal carbonate rocks. However, the 65.5 Ma Chicxulub meteorite impact in the northern Yucatan Peninsula excavated deep into the crust and brought crystalline basement fragments into the impact breccias. Common Pb isotopic data from impact melt and a granitic clast from drill core (Y6) are highly radiogenic, consistent with the Archaean derivation. A granodiorite clast in this breccia from drill core (Yaxcopoil-1) yielded a continuous range of concordant ²⁰⁶Pb/²³⁸U laser ablation inductively coupled plasma mass spectrometry zircon ages between 546 ± 5 Ma and 465 Ma, with three discordant zircons having ²⁰⁶Pb/²³⁸U ages between 130 Ma and 345 Ma. The ca. 546 Ma age is interpreted as the age of granodiorite intrusion, with younger ages representing variable Pb loss during melting associated with the meteorite impact. This is consistent with previous U–Pb zircon data that gave an upper intercept age of 550 ± 15 Ma at Chicxulub, which becomes 545 ± 5 Ma when combined with the zircon data from distal ejecta. Such arc rocks are absent in the southern Maya block, and in the neighbouring Oaxaquia terrane (s.s.) they are replaced by a 546 ± 5 Ma plume-related dike swarm. On the other hand, Ediacaran arc rocks continue through the peri-Gondwanan terranes of the Appalachians and Europe (Florida, Carolinia, Avalonia, Iberia, Armorica, Massif Central, Bohemia, and NW Africa). Arc magmatism in these areas ended between 570 Ma (Newfoundland) and 540 Ma (Carolinia/UK) as the subduction zone was replaced by a transform fault along the northern Gondwanan margin. This age range is synchronous with the two-stage birth of Iapetus, suggesting that both are related to major plate reorganization. The source of plume-related dikes may have been located at the rift–rift–transform triple junction between Laurentia, Baltica, and Gondwana.     

Comparative Dietary Diversity and Trophic Ecology of Two Estuarine Mesopredators

Quantifying the trophic dynamics of mesopredators in coastal habitats is an essential precursor to understanding their role in linking multiple trophic levels. Traditional dietary analyses may miss key aspects of a species’ feeding ecology and may thus fail to identify trophic linkages between predators and economically important prey populations. We applied stomach content and stable isotope analyses to estimate diet and trophic dynamics and investigated intraspecific dietary diversity of bonnetheads (Sphyrna tiburo) and red drum (Sciaenops ocellatus). Both juvenile and adult bonnetheads and juvenile red drum had diets comprised mainly of crustaceans, notably portunid crabs and penaeid shrimp, with varying degrees of dietary and isotopic niche overlap. Juvenile and adult bonnetheads had high dietary and isotopic niche overlap, whereas the degree of overlap between bonnetheads and red drum varied. Our findings indicate that bonnetheads are dietary specialists whereas red drum are dietary generalists. Further analysis identified intraspecific variability in the diet of each species; adult bonnetheads had the highest prey diversity whereas red drum had the lowest. We show that dietary and isotopic niche overlap and intraspecific variation in diet exist among juvenile and adult bonnetheads and juvenile red drum, though to varying degrees. Our findings demonstrate the importance of fully examining the trophic ecology of species that share habitats and resources, both at individual and population levels.     

Paleobiological Implications of the Isotopic Signatures (C,N) of Fossil Mammal Collagen in Scladina Cave (Sclayn, Belgium)

An isotopic investigation of upper Pleistocene mammal bones and teeth from Scladina cave (Sclayn, Belgium) demonstrated the very good quality of collagen preservation. A preliminary screening of the samples used the amount of nitrogen in whole bone and dentine in order to estimate the preserved amount of collagen before starting the extraction process. The isotopic abundances of fossil specimens from still-extant species are consistent with their trophic position. Moreover, the¹⁵N isotopic abundance is higher in dentine than in bone in bears and hyenas, a phenomenon already observed in modern specimens. These results demonstrate that the isotopic compositions of samples from Scladina cave can be interpreted in ecological terms. Mammoths exhibit a high¹⁵N isotopic abundance relative to other herbivores, as was the case in Siberian and Alaskan samples. These results suggest distinctive dietary adaptations in herbivores living in the mammoth steppe. Cave bears are clearly isotopically different from coeval brown bears, suggesting an ecological separation between species, with a pure vegetarian diet for cave bear and an omnivorous diet for brown bear.     

Lowland Maya water management practices: The household exploitation of rural wells

A hypothesis developed by Vernon Scarborough and endorsed and modified by Lisa Lucero and Anabel Ford proposes that lowland Maya elites centralized and coordinated political power by controlling access to water stored in large, centrally located reservoirs. The hypothesis presupposes that in the central and southern Maya lowlands, nonelites did not have access to viable alternative dry‐season water sources. This paper demonstrates that, in the east‐central and southwestern areas of the Maya lowlands, fault springs were an important source of water, particularly to rural peoples. After reviewing the evidence of Maya fault spring exploitation and documenting the hydrogeological conditions under which fault springs form, I describe wells that rural households built to expose fault springs and enhance their flow, including clay‐lined and stone‐lined shafts. Also documented are three well types found elsewhere in the Maya lowlands: (1) wells built to exploit permanent, generally shallow water tables; (2) wells dug to catch precipitation as it filtered down through bedrock; and (3) buk'teob, built to recover during the dry season the receding contents of pools that during the rainy season collect in aguadas. The dispersed distribution of Maya wells in rural settings and their frequent association with modest residential remains suggests that nonelite households managed them. The existence of Maya wells that supplied water to rural peoples through the dry season is inconsistent with the Scarborough‐Lucero‐Ford hypothesis. © 2004 Wiley Periodicals, Inc.     

Man and climate in the Maya lowlands

A 15-m sedimentary core from Lake Salpeten provides the first complete Holocene sequence for the lowlying Peten District, Guatemala. Today, Lake Salpeten is a brackish, calcium sulfate lake near saturation surrounded by tropical semievergreen forest. The basal pollen record depicts sparse juniper scrub surrounding a lake basin that held ephermal pools and halophytic marshes. The lake rapidly deepened to > 27 m in the early Holocene and may have been meromictic, because nearly 2 m of gypsum “mush” was deposited. Mesic forests were quickly established and persisted until the Maya entered the district 3000 yr ago and caused extensive deforestation. Any climatic information contained in the pollen record of the Maya period is thus masked, but a regional pollen sequence linked to the archaeological record is substantiated because environmental disturbance was pervasive. Local intensification of occupation and population growth are seen as an increased deposition of pollen of agricultural weeds and colluviation into the lake, while the Classic Maya collapse is marked by a temporary decline in Compositae pollen. Effects of perturbations induced by the Maya persist in the pollen and limnetic record 400 yr after the Spanish conquest.     

金红石U-Pb同位素稀释法定年技术的改进

介绍了金红石U-Pb定年方法,并对影响本底的各方面因素、同位素分馏效应、干扰峰影响等环节做了分析和讨论,提出了相关的流程改进措施,并利用改进的方法对大别山超高压榴辉岩中的金红石做了测定,获得了218.2±1.2 Ma的高精度金红石UPb年龄.     

Seasonal variation in kangaroo tooth enamel oxygen and carbon isotopes in southern Australia

Serial sampling of tooth enamel growth increments for carbon and oxygen isotopic analyses of Macropus (kangaroo) teeth was performed to assess the potential for reconstructing paleoseasonality. The carbon isotope composition of tooth enamel apatite carbonate reflects the proportional intake of C₃ and C₄ vegetation. The oxygen isotopic composition of enamel reflects that of ingested and metabolic water. Tooth enamel forms sequentially from the tip of the crown to the base, so dietary and environmental changes during the tooth's formation can be detected. δ¹³C and δ¹⁸O values were determined for a series of enamel samples drilled from the 3rd and 4th molars of kangaroos that were collected along a 900 km north–south transect in southern Australia. The serial sampling method did not yield pronounced seasonal isotopic variation patterns in Macropus enamel. The full extent of dietary isotopic variation may be obscured by attenuation of the isotopic signal during enamel mineralisation. Brachydont (low-crowned) Macropus teeth may be less sensitive to seasonal variation in isotopic composition due to time-averaging during mineralisation. However, geographic variations observed suggest that there may be potential for tracking latitudinal shifts in vegetation zones and seasonal environmental patterns in response to climate change.     

Problems of geological and isotopic age of the Okhotsk-Chukotsk Volcanogenic Belt (OCVB)

The working stratigraphic chart accepted for the Okhotsk-Chukotsk Volcanogenic Belt (OCVB) at the 3rd Interdepartmental Regional Stratigraphic Conference (IRSC) integrated data of the medium-scale geological survey, the established succession of endemic floras of the developing volcanic highland, and the results of palynological and magnetostratigraphic study (Resolutions of the 3rd…, 2003). The OCVB was formed during the middle Albian-Santonian (and initial Campanian probably). Sequences of the belt are attributed to the Buor-Kemyus (early-middle Albian), Arman (late Albian), Amka (Cenomanian), and Arkagala (Turonian-Santonian) phytostratigraphic horizons. The lack of data on relations between the horizons and fauna-bearing marine deposits is a serious obstacle for correlation of regional subdivisions with the general stratigraphic scale. The problem can be solved using geological methods of palynological and tephrochronological research. Isotopic ages of the OCVB rocks were determined applying the K-Ar and Rb-Sr isotopic dating in the early period and the Ar-Ar and U-Pb (SHRIMP) methods in recent years. The subdivision scheme of the OCVB volcanics based on the K-Ar relict and Rb-Sr isochron dates, which is accepted as addendum to the working stratigraphic chart, confirms in general the geological inferences concerning the OCVB age. The Ar-Ar and U-Pb dates (less than 100 determinations in total) obtained for the Okhotsk, Central Chukotsk, and Anadyr sectors of the OCVB external zone provoked opinions that the belt age should be radically revised. Analysis of new isotopic dates showed that they contradict in variable extent to geological data on the Okhotsk and Central Chukotsk sectors, whereas there is no significant discordance between isotopic and geological data on the Anadyr sector. Consequently, it can be empirically concluded that geological factors influenced the isotopic systems (“clock”). There is also a considerable discordance between the Ar-Ar and U-Pb isotopic dates. These uncertainties of the isotopic dating imply prematurity of idea to revise age of the OCVB.     

A review of human and natural changes in Maya Lowland wetlands over the Holocene

In the Maya Lowlands of Mexico, Belize, and Guatemala two main types of wetlands have played important roles in human history: bajos or intermittently wet environments of the upland, interior Yucatán and perennial wetlands of the coastal plains. Many of the most important Maya sites encircle the bajos, though our growing evidence for human–wetland interactions is still sparse. The deposits of these wetlands record two main eras of slope instability and wetland aggradation: the Pleistocene–Holocene transition as rainfall increased and forests eclipsed savannas and the Maya Preclassic to Classic as deforestation, land-use intensity, and drying increased. The ancient Maya adapted with terraces around these bajo margins but retracted in the Late Preclassic in some areas. The perennial wetlands of the coastal plains have different histories, and the first conceptual model of human–wetland interaction described intensive wetland agriculture in the Preclassic through Classic based on raised fields and canals. But a second model arose that interpreted the wetland stratigraphy and canals as more indicative of natural aggradation by accelerated erosion and gypsum precipitation that buried Archaic and Preclassic fields and there was little Classic era use. We present new data on a third and fourth model in this study. The third is a hybrid of the models one and two, including the Archaic to Preclassic aggradation of the second model, and the first model's Classic period fields and canals as piecemeal attempts by the Maya to adapt to these and other environmental changes. The fourth conceptual model describes a very Late/Terminal Classic, preplanned project on a floodplain. These wetland fields were short-lived, aggraded rapidly but with some reoccupation in the Postclassic. All of these new models display the burgeoning evidence for intricate Maya interactions with wetlands, and the diversity of evidence from the relatively few studies underscores the infancy of our understanding of Maya interaction with tropical wetlands.     

A new application of headspace single-drop microextraction technique for compound specific carbon isotopic determination of gasoline range hydrocarbons

In this study, headspace single-drop microextraction (HS-SDME) coupled with gas chromatography-isotope ratio mass spectrometry (GC-IRMS), was employed to determine compound specific carbon isotopic values (δ¹³C) of gasoline range hydrocarbons. The reproducibility of the method was found to be satisfactory. By comparison with the δ¹³C values of the twelve target compounds determined using direct injection of their n-C₁₆ solution, no obvious isotopic fractionation was observed during the HS-SDME procedures. Some parameters that could affect the carbon isotopic fractionation, such as ionic strength of working solutions and inlet split ratio, were examined. The results also suggest that these factors had no significant effect on the carbon isotopic determination of gasoline range hydrocarbons. The application of HS-SDME to a crude oil sample proved that this method could be a promising tool for the determination of carbon isotopic values of gasoline range hydrocarbons in oils or aqueous samples.