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1. Detecting Classic Maya Settlements with Lidar-Derived Relief Visualizations

   https://doi.org/10.3390/rs12172838  

   Thompson, Amy E. ( September 2020 , Remote Sensing)

   In the past decade, Light Detection and Ranging (lidar) has fundamentally changed our ability to remotely detect archaeological features and deepen our understanding of past human-environment interactions, settlement systems, agricultural practices, and monumental constructions. Across archaeological contexts, lidar relief visualization techniques test how local environments impact archaeological prospection. This study used a 132 km2 lidar dataset to assess three relief visualization techniques—sky-view factor (SVF), topographic position index (TPI), and simple local relief model (SLRM)—and object-based image analysis (OBIA) on a slope model for the non-automated visual detection of small hinterland Classic (250–800 CE) Maya settlements near the polities of Uxbenká and Ix Kuku’il in Southern Belize. Pedestrian survey in the study area identified 315 plazuelas across a 35 km2 area; the remaining 90 km2 in the lidar dataset is yet to be surveyed. The previously surveyed plazuelas were compared to the plazuelas visually identified on the TPI and SLRM. In total, an additional 563 new possible plazuelas were visually identified across the lidar dataset, using TPI and SLRM. Larger plazuelas, and especially plazuelas located in disturbed environments, are often more likely to be detected in a visual assessment of the TPI and SLRM. These findings emphasize the extent and densitymore »of Classic Maya settlements and highlight the continued need for pedestrian survey to ground-truth remotely identified archaeological features and the impact of modern anthropogenic behaviors for archaeological prospection. Remote sensing and lidar have deepened our understanding of past human settlement systems and low-density urbanism, processes that we experience today as humans residing in modern cities.« less
2. IDENTIFYING LOCAL AND NON-LOCAL POTTERY IN THREE TOMBS AT UXBENKÁ, TOLEDO DISTRICT: RESULTS OF THIN SECTION ANALYSIS

   Jordan, Jillian ; Prufer, Keith ( January 2020 , Research reports in Belizean archaeology)

   Southern Belize has received less archaeological attention than other areas due in large part to its remote location. However, the difficulty in accessing the area in recent times does not necessarily equate to isolation for the Classic Period Maya who lived in what is now the Toledo District. This paper discusses petrographic data collected on ceramic vessels recovered from burial contexts at Uxbenká, Belize. The partial and reconstructed whole vessels from these primary contexts include locally produced vessels that are stylistically and technologically unique to the southern Belize region and vessels produced elsewhere. We use these data to evaluate how local Uxbenká potters produced ceramic vessels for local consumption and to identify long-distance interaction networks between Uxbenká and other regions of the Maya Lowlands. Our data indicate that most of the pottery at Uxbenká was produced locally. However, elite tombs often include both local and non-local vessels. The elites of Uxbenká engaged in interaction with people living much farther afield in regions like the Belize River Valley and possibly Guatemala.
3. The Paleoindian Chronology of Tzib Te Yux Rockshelter in the Rio Blanco Valley of Southern Belize.

   Prufer, Keith ; Meredith, Clayton ; Alsgaard, Asia ; Dennehy, Timothy ; Kennett, Douglas ( January 2017 , Research reports in Belizean archaeology)

   With very little known about preceramic occupations in Belize we present the chronology of a small rockshelter in southern Belize that has clear evidence of human activity extending back to the late Pleistocene. The shelter is located along the Rio Blanco valley less than 2 km from the site of Uxbenká. Data collected from four seasons of excavation indicate that the first humans began exploiting local resources, including freshwater snails (jute) by 10,500 BC and were drawn to the rockshelter by its location near fresh water and stone tool resources. Jute processing was a major part of the use of the shelter and continued likely through the Classic Period. Unfortunately, the upper levels of the archaic and Classic Maya period are mixed or were removed, possibly for the carbonate jute shells, likely during the occupation of Uxbenká.
4. Drip water δ18O variability in the northeastern Yucatán Peninsula, Mexico: implications for tropical cyclone detection and rainfall reconstruction from speleothems.

   https://doi.org/https://doi.org/10.1016/j.gca.2020.07.008  

   Lases-Hernandez F., Medina-Elizalde M. ( July 2020 , Geochimica et cosmochimica acta)

   This study examines the oxygen isotopic composition (δ18O values) of drip water, rainfall, and groundwater in the Río Secreto Cave system, located in the Yucatán Peninsula, Mexico. The main motivation of this study was to determine the implications of drip water hydrology for the reconstruction of rainfall and for the detection of droughts and tropical cyclones from stalagmite δ18O records. Monitoring of environmental and isotopic conditions was conducted for two years, from June 2017 to April 2019. This study provides the first instrumental evidence of an “amount effect” on interannual timescales in the Yucatán Peninsula. Observed bi-weekly to interannual variability in drip water δ18O values can be explained for individual drips by different integrations of rainfall amount in the time domain. Drip sites within two chambers (stations A and B) integrate 4 to 15 months of rainfall accumulation. Within a third chamber (station LF) one drip site reflects the annual rainfall isotopic cycle with a positive offset and another, the largest rainfall events. During epikarst infiltration, the integration of rainfall amount by drip water reservoirs determines the degree to which they "dilute" a tropical cyclone (TC) isotopic signature. TCs can be detected particularly when: (1) the water volume of themore »reservoir is low, such as during a persistent drought, and; (2) TCs have a sufficiently distinct isotopic signal relative to that of the reservoir prior to the event. TC isotopic signals can "filter through" the system on time scales shorter than the integration time of the reservoir, on the order of a week, in most of the reservoirs examined. In Río Secreto Cave reconstructing precipitation amount and detecting the TC isotopic signatures from stalagmite δ18O are possible, but not in all cases. Our analysis shows that stalagmite δ18O records are more likely to underestimate the magnitude of annual-scale droughts following normal hydroclimate conditions and more likely to record TCs during multiyear droughts than during normal or wet periods. Drip water monitoring results suggest that available stalagmite δ18O records from the Maya lowlands might be underestimating the intensity of paleo-drought events, such as the Terminal Classic droughts associated with the disintegration of the Maya civilization. This study complements the results from Lases-Hernandez et al. (2019) comparing two different sampling protocols and highlights the importance of conducting multiyear monitoring of drip water and rainfall in order to interpret stalagmite δ18O as a paleoclimate proxy.« less
5. The Cape Town “Day Zero” drought and Hadley cell expansion

   https://doi.org/10.1038/s41612-019-0084-6  

   Burls, Natalie J. ; Blamey, Ross C. ; Cash, Benjamin A. ; Swenson, Erik T. ; Fahad, Abdullah al ; Bopape, Mary-Jane M. ; Straus, David M. ; Reason, Chris J. C. ( August 2019 , npj Climate and Atmospheric Science)

   In early 2018, Cape Town (population ~3.7 million) was at risk of being one of the first major metropolitan areas in the world to run out of water. This was due to a severe multi-year drought that led to the levels of supply dams falling to an unprecedented low. Here we analyze rainfall data from the city catchment areas, including rare centennial records from the surrounding region, to assess the severity of the 2015–2017 drought. We find that there has been a long-term decline in the number of winter rainfall days, but this trend has been generally masked by fluctuations in rainfall intensity. The recent drought is unprecedented in the centennial record and represents a combination of the long-term decline in rainfall days and a more recent decline in rainfall intensity. Cold fronts during the winter months are responsible for most of the rainfall reaching Cape Town and our analysis shows no robust regional trend in the number of fronts over the last 40 years. Rather, the observed multidecadal decline in rainfall days, which threatens to increase the occurrence of severe drought, appears to be linked to a decrease in the duration of rainfall events associated with cold fronts.more »This change in rainfall characteristics associated with fronts appears to be linked to Hadley Cell expansion seen across the Southern Hemisphere and an increasing trend in post-frontal high-pressure conditions that suppress orographically enhanced rainfall.

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