LiDAR coverage of a large contiguous area within the Mirador-Calakmul Karst Basin (MCKB) of north... more LiDAR coverage of a large contiguous area within the Mirador-Calakmul Karst Basin (MCKB) of northern Guatemala has identified a concentration of Preclassic Maya sites (ca. 1000 B.C.-A.D. 150) connected by causeways, forming a web of implied social, political, and economic interactions. This article is an introduction to one of the largest, contiguous, regional LiDAR studies published to date in the Maya Lowlands. More than 775 ancient Maya settlements are identified within the MCKB, and 189 more in the surrounding karstic ridge, which we condensed into 417 ancient cities, towns, and villages of at least six preliminary tiers based on surface area, volumetrics, and architectural configurations. Many tiered sites date to the Middle and Late Preclassic periods, as determined by archaeological testing, and volumetrics of contemporaneously constructed and/or occupied architecture with similar morphological characteristics. Monumental architecture, consistent architectural formats, specific site boundaries, water management/ collection facilities, and 177 km of elevated Preclassic causeways suggest labor investments that defy organizational capabilities of lesser polities and potentially portray the strategies of governance in the Preclassic period. Settlement distributions, architectural continuities, chronological contemporaneity, and volumetric considerations of sites provide evidence for early centralized administrative and socioeconomic strategies within a defined geographical region.
This paper classifies the karst landscapes of the Peté n Plateau and defines the Mirador-Calakmul... more This paper classifies the karst landscapes of the Peté n Plateau and defines the Mirador-Calakmul Karst Basin by illustrating the distribution of its karst hydrologic features. Archaeological and spatial research of the Mirador-Calakmul area of Guatemala and Mexico has shown it to be a karst basin with geopolitical implications. Current research characterizes the karst landscapes of the Peté n Plateau, maps the distribution of karst hydrologic features, and delineates the basin in geomorphological terms. To further this aim, multiple forms of remote sensing data including orthophotographs, a satellite Digital Elevation Model, satellite multispectral images, and Light Detection and Ranging (LiDAR) data have been integrated to interpret the karst features in the study area. Outcrop study and thin section analysis of the upper Buena Vista Formation document that the dominant lithologies are a shallow water algal boundstone interbedded with terrestrial caliche. Karst landforms have been mapped over the Peté n Plateau and we identify five karst landscapes, the largest of which is a fluviokarst landscape dominated by karst valleys. We further map karst hydrologic features including seasonal swamps, dolines, intermittent lakes, intermittent streams, solution-enhanced fractures, and springs all of which are characteristic of drainage basins. Boundaries of the karst basin are mapped from multiple lines of evidence including distribution of the karst valleys, a line of springs along the western boundary of the fluviokarst landscape, and a surface drainage analysis. We capture and classify hydrologic data points and develop a regional groundwater map that indicates subsurface flow from east to west within the basin. A drainage map illustrates the extensive system of karst valleys, boundaries, and inferred groundwater flow paths of the Mirador-Calakmul Karst Basin. It was within this geomorphological setting that the ancient Maya developed an extensive civilization during the Middle and Late Preclassic periods (1000 BCE-150 CE).
We have developed a new experimental procedure in order to study the role of water content in the... more We have developed a new experimental procedure in order to study the role of water content in the acquisition of post-depositional detrital remanent magnetism by a sediment. The procedure leads to the determination of the magnetic direction recorded by a sediment as a function of the water content present when that sediment experiences a change in the direction of an
Compressional waves are sensitive to the type of pore fluid within rocks, but shear waves are onl... more Compressional waves are sensitive to the type of pore fluid within rocks, but shear waves are only slightly affected by changes in fluid type. This suggests that a comparison of compressional- and shear-wave seismic data recorded over a prospect may allow an interpreter to discriminate between gas-related anomalies and those related to lithology. This case study documents that where a compressional-wave 'bright spot' or other direct hydrocarbon indicator is present, such a comparison can be used to verify the presence of gas. In practice, the technique can only be used for a qualitative evaluation. However, future improvement of shear-wave data quality may enable the use of more quantitative methods as well.
A magnetic polarity zonation has been established for the upper Castaic Formation and lower Ridge... more A magnetic polarity zonation has been established for the upper Castaic Formation and lower Ridge Route and Peace Valley Formations of the Ridge Basin of the central Transverse Ranges of southern California. The zonation is based on the analysis of over 1900 samples from 669 sites in the 5800 m thick sedimentary sequence. Rock magnetic studies provide evidence that the carrier of the primary remanence is magnetite and that the magnetization was acquired at or shortly after deposition of the sediment. Although many samples contain a secondary, normal overprint, systematic analysis of the changes in direction upon demagnetization leads to an accurate determination of the original polarity. Thirteen polarity intervals are recognized. On the basis of biostratigraphic constraints imposed by a marine invertebrate faunaat the base of the sequence and a terrestrial vertebrate fauna at the top, the magnetic polarity zonation can be correlated to the magnetic polarity time scale. The studied interval extends from the Epoch 5/Epoch 6 boundary to the middle of Epoch 8. Polarity changes within the studied interval represent chronostratigraphic horizons which can be used to analyze tectonic and sedimentologic processes which are recorded in the sediments of the Ridge Basin. The locus of the tectonic activity within the basin has been dated as occurring on the Clearwater fault from 8.1 to 7.8 m.y. ago, on the Liebre faultfrom 7.3 to 6.1 m.y. ago and on the North Liebre fault from 6.0 to 5.0 m.y. ago. During this entire period of time, the San Gabriel fault on the western margin of the basin was continuously active, and a period of particularly vigorous activity has been dated at 7.3 to 7.0 m.y. The mean declinations of samples from the normal magnetozones provide no evidence for the existence of a major rotation of the Ridge Basin subsequent to about 8.5 m.y. ago. Sedimentation rates for interbedded sandstone and shale units within the basin have been separately determined as 0.2 m/1000 years and 3.0 m/1000 years, respectively. The water content of certain deformed structures within the sequence has been determined to have been 35% and 40% at the time of deformation.
This paper classifies the karst landscapes of the Petén Plateau and defines the Mirador-Calakmul ... more This paper classifies the karst landscapes of the Petén Plateau and defines the Mirador-Calakmul Karst Basin by illustrating the distribution of its karst hydrologic features. Archaeological and spatial research of the Mirador-Calakmul area of Guatemala and Mexico has shown it to be a karst basin with geopolitical implications. Current research characterizes the karst landscapes of the Petén Plateau, maps the distribution of karst hydrologic features, and delineates the basin in geomorphological terms. To further this aim, multiple forms of remote sensing data including orthophotographs, a satellite Digital Elevation Model, satellite multispectral images, and Light Detection and Ranging (LiDAR) data have been integrated to interpret the karst features in the study area. Outcrop study and thin section analysis of the upper Buena Vista Formation document that the dominant lithologies are a shallow water algal boundstone interbedded with terrestrial caliche. Karst landforms have been m...
Shear waves differ from compressional waves in that their velocity is not significantly affected ... more Shear waves differ from compressional waves in that their velocity is not significantly affected by changes in the fluid content of a rock. Because of this relationship, a gas‐related compressional‐wave “bright spot” or direct hydrocarbon indicator will have no comparable shear‐wave anomaly. In contrast, a lithology‐related compressional‐wave anomaly will have a corresponding shear‐wave anomaly. Thus, it is possible to use shear‐wave seismic data to evaluate compressional‐wave direct hydrocarbon indicators. This case study presents data from Myrnam, Alberta which exhibit the relationship between compressional‐ and shear‐wave seismic data over a gas reservoir and a low‐velocity coal.
Stratigraphic correlations from wells tied to high resolution seismic data offer specific constra... more Stratigraphic correlations from wells tied to high resolution seismic data offer specific constraints for interpreting tectonic events. Paleogeographic models based on these interpretations can be used to define the paleobathymetry of a basin at specific points in time and space, providing critical constraints on the rifting and subsidence history that are not available from regional structural interpretations. Based on detailed work undertaken to define the play characteristics of the Campos basin, we propose a new subsidence history for the critical presalt to salt transition time. Mapping of the “synrift” to “sag” transitional stratigraphy indicates a significant erosional unconformity at the base salt level across the outer Campos hinge in the southern Campos basin that results in the removal of the uppermost presalt section and portions of the underlying coquina section. We propose that this erosional unconformity truncates presalt stratigraphy where the basin has undergone sho...
LiDAR coverage of a large contiguous area within the Mirador-Calakmul Karst Basin (MCKB) of north... more LiDAR coverage of a large contiguous area within the Mirador-Calakmul Karst Basin (MCKB) of northern Guatemala has identified a concentration of Preclassic Maya sites (ca. 1000 B.C.-A.D. 150) connected by causeways, forming a web of implied social, political, and economic interactions. This article is an introduction to one of the largest, contiguous, regional LiDAR studies published to date in the Maya Lowlands. More than 775 ancient Maya settlements are identified within the MCKB, and 189 more in the surrounding karstic ridge, which we condensed into 417 ancient cities, towns, and villages of at least six preliminary tiers based on surface area, volumetrics, and architectural configurations. Many tiered sites date to the Middle and Late Preclassic periods, as determined by archaeological testing, and volumetrics of contemporaneously constructed and/or occupied architecture with similar morphological characteristics. Monumental architecture, consistent architectural formats, specific site boundaries, water management/ collection facilities, and 177 km of elevated Preclassic causeways suggest labor investments that defy organizational capabilities of lesser polities and potentially portray the strategies of governance in the Preclassic period. Settlement distributions, architectural continuities, chronological contemporaneity, and volumetric considerations of sites provide evidence for early centralized administrative and socioeconomic strategies within a defined geographical region.
This paper classifies the karst landscapes of the Peté n Plateau and defines the Mirador-Calakmul... more This paper classifies the karst landscapes of the Peté n Plateau and defines the Mirador-Calakmul Karst Basin by illustrating the distribution of its karst hydrologic features. Archaeological and spatial research of the Mirador-Calakmul area of Guatemala and Mexico has shown it to be a karst basin with geopolitical implications. Current research characterizes the karst landscapes of the Peté n Plateau, maps the distribution of karst hydrologic features, and delineates the basin in geomorphological terms. To further this aim, multiple forms of remote sensing data including orthophotographs, a satellite Digital Elevation Model, satellite multispectral images, and Light Detection and Ranging (LiDAR) data have been integrated to interpret the karst features in the study area. Outcrop study and thin section analysis of the upper Buena Vista Formation document that the dominant lithologies are a shallow water algal boundstone interbedded with terrestrial caliche. Karst landforms have been mapped over the Peté n Plateau and we identify five karst landscapes, the largest of which is a fluviokarst landscape dominated by karst valleys. We further map karst hydrologic features including seasonal swamps, dolines, intermittent lakes, intermittent streams, solution-enhanced fractures, and springs all of which are characteristic of drainage basins. Boundaries of the karst basin are mapped from multiple lines of evidence including distribution of the karst valleys, a line of springs along the western boundary of the fluviokarst landscape, and a surface drainage analysis. We capture and classify hydrologic data points and develop a regional groundwater map that indicates subsurface flow from east to west within the basin. A drainage map illustrates the extensive system of karst valleys, boundaries, and inferred groundwater flow paths of the Mirador-Calakmul Karst Basin. It was within this geomorphological setting that the ancient Maya developed an extensive civilization during the Middle and Late Preclassic periods (1000 BCE-150 CE).
We have developed a new experimental procedure in order to study the role of water content in the... more We have developed a new experimental procedure in order to study the role of water content in the acquisition of post-depositional detrital remanent magnetism by a sediment. The procedure leads to the determination of the magnetic direction recorded by a sediment as a function of the water content present when that sediment experiences a change in the direction of an
Compressional waves are sensitive to the type of pore fluid within rocks, but shear waves are onl... more Compressional waves are sensitive to the type of pore fluid within rocks, but shear waves are only slightly affected by changes in fluid type. This suggests that a comparison of compressional- and shear-wave seismic data recorded over a prospect may allow an interpreter to discriminate between gas-related anomalies and those related to lithology. This case study documents that where a compressional-wave 'bright spot' or other direct hydrocarbon indicator is present, such a comparison can be used to verify the presence of gas. In practice, the technique can only be used for a qualitative evaluation. However, future improvement of shear-wave data quality may enable the use of more quantitative methods as well.
A magnetic polarity zonation has been established for the upper Castaic Formation and lower Ridge... more A magnetic polarity zonation has been established for the upper Castaic Formation and lower Ridge Route and Peace Valley Formations of the Ridge Basin of the central Transverse Ranges of southern California. The zonation is based on the analysis of over 1900 samples from 669 sites in the 5800 m thick sedimentary sequence. Rock magnetic studies provide evidence that the carrier of the primary remanence is magnetite and that the magnetization was acquired at or shortly after deposition of the sediment. Although many samples contain a secondary, normal overprint, systematic analysis of the changes in direction upon demagnetization leads to an accurate determination of the original polarity. Thirteen polarity intervals are recognized. On the basis of biostratigraphic constraints imposed by a marine invertebrate faunaat the base of the sequence and a terrestrial vertebrate fauna at the top, the magnetic polarity zonation can be correlated to the magnetic polarity time scale. The studied interval extends from the Epoch 5/Epoch 6 boundary to the middle of Epoch 8. Polarity changes within the studied interval represent chronostratigraphic horizons which can be used to analyze tectonic and sedimentologic processes which are recorded in the sediments of the Ridge Basin. The locus of the tectonic activity within the basin has been dated as occurring on the Clearwater fault from 8.1 to 7.8 m.y. ago, on the Liebre faultfrom 7.3 to 6.1 m.y. ago and on the North Liebre fault from 6.0 to 5.0 m.y. ago. During this entire period of time, the San Gabriel fault on the western margin of the basin was continuously active, and a period of particularly vigorous activity has been dated at 7.3 to 7.0 m.y. The mean declinations of samples from the normal magnetozones provide no evidence for the existence of a major rotation of the Ridge Basin subsequent to about 8.5 m.y. ago. Sedimentation rates for interbedded sandstone and shale units within the basin have been separately determined as 0.2 m/1000 years and 3.0 m/1000 years, respectively. The water content of certain deformed structures within the sequence has been determined to have been 35% and 40% at the time of deformation.
This paper classifies the karst landscapes of the Petén Plateau and defines the Mirador-Calakmul ... more This paper classifies the karst landscapes of the Petén Plateau and defines the Mirador-Calakmul Karst Basin by illustrating the distribution of its karst hydrologic features. Archaeological and spatial research of the Mirador-Calakmul area of Guatemala and Mexico has shown it to be a karst basin with geopolitical implications. Current research characterizes the karst landscapes of the Petén Plateau, maps the distribution of karst hydrologic features, and delineates the basin in geomorphological terms. To further this aim, multiple forms of remote sensing data including orthophotographs, a satellite Digital Elevation Model, satellite multispectral images, and Light Detection and Ranging (LiDAR) data have been integrated to interpret the karst features in the study area. Outcrop study and thin section analysis of the upper Buena Vista Formation document that the dominant lithologies are a shallow water algal boundstone interbedded with terrestrial caliche. Karst landforms have been m...
Shear waves differ from compressional waves in that their velocity is not significantly affected ... more Shear waves differ from compressional waves in that their velocity is not significantly affected by changes in the fluid content of a rock. Because of this relationship, a gas‐related compressional‐wave “bright spot” or direct hydrocarbon indicator will have no comparable shear‐wave anomaly. In contrast, a lithology‐related compressional‐wave anomaly will have a corresponding shear‐wave anomaly. Thus, it is possible to use shear‐wave seismic data to evaluate compressional‐wave direct hydrocarbon indicators. This case study presents data from Myrnam, Alberta which exhibit the relationship between compressional‐ and shear‐wave seismic data over a gas reservoir and a low‐velocity coal.
Stratigraphic correlations from wells tied to high resolution seismic data offer specific constra... more Stratigraphic correlations from wells tied to high resolution seismic data offer specific constraints for interpreting tectonic events. Paleogeographic models based on these interpretations can be used to define the paleobathymetry of a basin at specific points in time and space, providing critical constraints on the rifting and subsidence history that are not available from regional structural interpretations. Based on detailed work undertaken to define the play characteristics of the Campos basin, we propose a new subsidence history for the critical presalt to salt transition time. Mapping of the “synrift” to “sag” transitional stratigraphy indicates a significant erosional unconformity at the base salt level across the outer Campos hinge in the southern Campos basin that results in the removal of the uppermost presalt section and portions of the underlying coquina section. We propose that this erosional unconformity truncates presalt stratigraphy where the basin has undergone sho...
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