Abstract The record of igneous activity (magmatism and volcanism) can significantly affect natural resource exploration and exploitation, including the search for hydrocarbons, critical minerals, natural hydrogen and geothermal energy sources, as well as using mafic igneous rocks as storage sites for CO 2 . These effects will vary depending on the nature and timing of the activity, the structural framework and the crustal architecture of the affected country-rock. To understand these effects and the interplay with other factors, we must first know the igneous record's distribution, timing, and petrology. In this paper, we describe a new geospatial database of the igneous rock record designed to provide a baseline digital resource that is application-agnostic and can be applied across the broadest range of research and resource exploration activities. We discuss the challenges we have faced and solved at each of the three main stages of geospatial mapping: database design, database population and database visualization. This includes the importance of a comprehensive audit trail so that users can differentiate between well and poorly-constrained interpretations, helping identify areas requiring additional work and data acquisition. The result is a geospatial database that will facilitate a better understanding of the Earth system and natural resource exploration.

Abstract Faults and folds are the clearest expressions of deformation we can observe directly in the rock record. This is visualized on 2D maps through the geometry of outcrop patterns and lines or polygons with marker symbols indicating different kinematics. But the record of deformation is 4D, and faults and folds represent only the products of deformation, not the processes responsible. Understanding the evolution of the 3D structural framework through time is fundamental for all forms of subsurface exploration across the energy transition. The aim of this paper is to show how 2D geospatial databases can represent the 4D deformational record. This is by capturing the three components of deformation: the initial state of the crustal architecture to be deformed (the pre-deformational crustal facies and structural framework), the processes responsible for the deformation (geodynamics), and the products of the deformation (folds, faults, magmatism and crustal facies). Deformation is not limited to a single tectonic cycle. Within each cycle, it is time-transgressive and highly variable spatially. By evolving these 2D geospatial databases through time using restoration and plate modelling, we can better understand the 4D complexity of deformation and how this impacts exploration.

Abstract Transform margins are a function of the pre-existing crustal architecture (pre-transform) and the interplay of syn- and post-transform geodynamic processes. We use a suite of geospatial databases to investigate four transform margins: East Africa (Davie Deformational Zone, DDZ), Equatorial Africa, and the South African and Falkland (Malvinas) margins (Agulhas–Falkland Fracture Zone, AFFZ). The East African margin is the most complex of the four. This is a consequence of Late Jurassic–Early Cretaceous transform motion affecting highly heterogeneous crust, and post-transform deformation that varies along the margin. Equatorial Africa most closely adheres to traditional definitions of ‘transform margins’, but actually comprises two principal transform systems – the Romanche and St Pauls, dictated by the pre-transform distribution of mobile belts and West African craton. All four margins are spatially associated with volcanism, and each exhibits narrow uplifts associated with transpression or transtension. But the causal relationship of these features with transform processes differ. Volcanism along the East African margin is pre- and post-transform. Syn-transform volcanism on the AFFZ is spatially limited, with the AFFZ possibly acting as a conduit for magmatism rather than as a causal driver. Transform margins are varied and complex and require an understanding of pre-, syn- and post-transform geodynamics.

It is self-evident that a better understanding of depositional systems and analogs leads to better inputs for geological models and better assessment of risk for plays and prospects in hydrocarbon exploration, as well as enhancing interpretations of earth history. Depositional environments–clastic and carbonate, fine- and coarse-grained, continental, marginal marine and deep marine–show latitudinal variations, which are sometimes extreme. Most familiar facies models derive from temperate and, to a lesser extent, tropical examples. By comparison, depositional analogs from higher latitudes are sparser in number and more poorly understood. Numerous processes are amplified and/or diminished at higher latitudes, producing variations in stratigraphic architecture from more familiar depositional “norms.” The joint AAPG/SEPM Hedberg Conference held in Banff, Alberta, Canada in October 2014 brought together broad studies looking at global databases to identify differences in stratigraphic models and sedimentary concepts that arise due to differences in latitude and to search for insights that may be applicable for subsurface interpretations. The articles in this Special Publication represent a cross-section of the work presented at the conference, along with the abstracts of the remaining presentations. This volume should be of great interest to all those working with stratigraphic models and sedimentary concepts.

Abstract: In 2014, a joint American Association for Petroleum Geologists/Society for Sedimentary Geology (AAPG/SEPM) sponsored Hedberg Conference was convened in Banff, Alberta, Canada, to investigate the impact of latitude on sedimentary systems and the facies models that geologists use to explain outcrop, core, and subsurface observations. This research conference, entitled Latitudinal Controls on Stratigraphic Models and Sedimentary Concepts , investigated the range of depositional systems from shallow to deep marine, and carbonates to clastics, in order to answer the question: Are current concepts and models biased toward mid- and low-latitude systems? The goals of the research symposium were (1) to identify differences in stratigraphic models and sedimentary concepts that arise due to differences in latitude and (2) to search for insights that may be applicable for subsurface interpretations. The articles included in this volume represent a cross-section of the work presented at the conference. Also included are abstracts of the remaining presentations.

Abstract: Approximately 22 Gt of siliciclastic sediment are delivered to the coastal ocean each year across the Earth’s latitude-controlled climate zones. Latitude effects are seen as controls on physical and biogeochemical weathering and thus sediment production; latitude effects also influence precipitation and wind patterns and impact sediment transport through, for example, river-water density and thus through the particle settling velocities of the suspended load. Glacial transport of sediment, including subglacial processes, meltwater, and iceberg rafting, dominates polar regions (10% of land surfaces). Subpolar regions (21% of the global land surface) include many nonglacial environments receiving low intensity rainfall and with low levels of sediment production (physical weathering) and fluvial transport. Their coastal regions are dominated by storm waves modulated by seasonal sea ice. Temperate regions (14%) are zones of moderate sediment production and fluvial transport, regional pockets of eolian transport, and coastal zones highly influenced by storm waves under the westerlies. The subtropical regions (18%) experience high rates of sediment production, moderate rates of precipitation, high rates of eolian transport via the trade winds (North Africa accounts for the majority of the global dust flux), and coastal zones heavily influenced by both swells and storm waves. The tropical region comprises the largest land mass (37%), with very high rates of precipitation (via the InterTropical Convergence Zone [ITCZ]) and sediment production (from biogeochemical weathering), high rates of fluvial clay and silt and sand transport, moderate levels of eolian transport, and swell-dominated coasts. Preservation of woody debris in the tropics is much smaller than in other climatic zones. Tropical river basins can produce and transport 2.5 times more sediment than a similar scale basin located in a temperate region and 12 times more sediment than a similar scale Arctic basin. Both eolian and glacial transport rates were an order of magnitude larger under ice age conditions, and such conditions repeatedly occurred during the past several million years.

Abstract: A common belief about tidal sedimentation is that tides are always larger near the equator and negligible at high latitudes. This belief appears to be based on equilibrium tidal theory that predicts the existence of two ocean–surface bulges centered at low latitudes; however, it is a misconception because this theory is a poor model for real-world tides. Instead, the tide behaves as a set of shallow-water waves that are guided around the world by the continents. Tidal ranges and tidal-current speeds increase as the tidal wave propagates onto and across continental shelves; especially large ranges and fast currents can occur in coastal embayments and in straits that join two larger bodies of water. Models of real-world tides today demonstrate that tides in shallow water (<100 m) have amplitude peaks at 50° N to 70° N and 50° S to 60° S that are associated with especially wide continental shelves and coastal embayments in which the tidal wave is close to resonance. The small tides characterizing most polar areas today are the result of local geomorphic features: the Arctic Ocean is too small to have its own tide and has only a small connection to the Atlantic Ocean that prevents effective northward propagation of the tidal wave, and Antarctica has narrow and deep continental shelves that do not accentuate the tide. Nevertheless, there are local areas in both the Arctic and Antarctic with favorable geomorphology that have macrotidal ranges. Thus, the latitudinal distribution of large tides is contingent on the plate-tectonic and sea-level history of the earth and changes over geologic time as the configuration of the ocean basins and the geometry of the flooded shelves change. The latitudinal variation of the strength of the Coriolis effect has a second-order influence on tidal dynamics, with the degree of tidal-range asymmetry across a basin potentially being larger at higher latitudes. The offshore extent of large coastal tidal ranges decreases at higher latitudes because the increased Coriolis effect leads to the tidal wave being more strongly banked-up against the shoreline. Diurnal, topographically trapped vorticity waves that can generate large tidal currents in shelf-edge water depths are also limited to middle to high latitudes. The presence of ice in polar areas also has an influence on tidal dynamics. Sea ice causes a small decrease in tidal range, whereas thick, floating ice shelves can cause dramatic increases in tidal range and tidal-current speeds, at least locally, as a result of the decrease in the cross-sectional area of the water beneath the ice shelves. Because coastal sedimentation is controlled by the relative importance of tidal currents and waves, the abundance of tide-dominated deposits might not reflect perfectly the latitudinal distribution of large tides. Thus, the small size of waves in the equatorial zone appears to cause preferential development of tide-dominated coastal zones near the equator, whereas wave dominance might be higher at midlatitudes because of the higher level of storminess, regardless of the latitudinal distribution of large tides.

Abstract: Photozoan and heterozoan carbonate systems differ in their biotic assemblages and depositional facies distribution. These, in turn, control their response to relative sea-level change, which affects stratigraphic architecture. Understanding the controls over the occurrence of different carbonate types is important when interpreting the fossil record. The differentiation of carbonate systems today into photozoan and heterozoan assemblages is directly dependent on the environmental requirements of the biocalcifiers active in the modern world. Because biocalcification mechanisms and environmental requirements have changed through time, it becomes increasingly difficult to apply this differentiation to older carbonate systems. This paper reviews general controls over the distribution of biotic assemblages in the modern world, investigating the major limiting factors affecting carbonate assemblages. Selected examples from icehouse and greenhouse time intervals are also discussed to highlight the effects of major limiting factors in the geological past. Icehouse times are characterized by stronger temperature and nutrient gradients, with environments spanning a larger spread of possible conditions. Times of climatic changeover are recorded by broad community shifts from the photozoan to heterozoan–photozoan transition. Greenhouse times, conversely, are characterized by gentler temperature gradients and biota suggesting that mesotrophic conditions were more widespread. This translates to a higher chance to find an expanded occurrence of heterozoan–photozoan transitional settings. Carbonate systems, with their unique biological and geochemical characterization, have a still largely unexplored potential to provide a record of Earth history events that have no modern analogues. However, it is critical to be fully aware of the factors and processes operating at different timescales that have an effect on biogenic assemblages and carbonate systems. The use of the terms photozoan and heterozoan must be used very critically going back in time. Rather than simply applying one model, the intrinsic complexities of carbonate systems require a detailed understanding of how and where sediment is produced, and eventually transported and deposited, before reliable paleoenvironmental scenarios can be constructed.

Abstract: Comparison of modern and ancient river deposits shows that both seasonally and interannually highly variable discharge results in distinct sedimentary facies and architecture in the monsoonal and subtropical river deposits, as compared to the perennial precipitation zone rivers. The monsoon zone and subtropical river deposits share most facies and architectural characteristics. The differences are mainly limited to biogenic and pedogenic features, such as in-channel vegetation and vegetation-induced sedimentary structures in rivers in subhumid subtropics. Extremely flashy rivers in arid and semiarid subtropics with highly intermittent precipitation also stand apart by the resemblance with megaflood deposits due to the dominance of Froude supercritical flow sedimentary structures and rapid deposition of suspended sediment. The distinct sedimentary characteristics of the monsoonal and subtropical rivers can be used as a climate proxy. However, they primarily reflect the precipitation pattern, rather than specific latitude or climate zone. Moreover, differences in past climates, as compared to the modern conditions, cause variability in the latitudinal distribution of monsoonal and subtropical precipitation zones throughout the geological history. Arctic rivers also experience seasonally highly variable discharge and display sedimentary characteristics that are partially similar to those of the monsoon zone and subtropical rivers.

Abstract: Using a script that automatically calculates sinuosity and radius of curvature for multiple bends on sinuous channel centerlines, we have assembled a new data set that allows us to reevaluate the relationship between latitude and submarine channel sinuosity. Sinuosity measurements on hundreds of channel bends from nine modern systems suggest that there is no statistically significant relationship between latitudinal position and channel sinuosity. In addition, for the vast majority of submarine channels on Earth, using flow velocities that are needed to transport the coarse-grained sediment found in channel thalwegs, estimates of the curvature-based Rossby number are significantly larger than unity. In contrast, low flow velocities that characterize the upper parts of turbidity currents in submarine channels located at high latitudes can easily result in Rossby numbers of less than one; this is the reason why levee deposits are often highly asymmetric in such channels. However, even in channels with asymmetric levees, the sinuosity of the thalweg is often obvious and must have developed as the result of an instability driven by the centrifugal force. Analysis of a simple centerline-evolution model shows that the increase in channel curvature precedes the increase in sinuosity and that low sinuosities are already associated with large curvatures. This suggests that the Coriolis effect is unlikely to be responsible for the low sinuosities observed in certain systems.

Abstract: Fjord valleys are carved during glaciation and then form local sediment sinks, which fill during retreat of the ice. Thus fjord valleys appear analogous to lower-latitude incised valleys, but they are remarkably different because fjords experience isostatic rebound during deglaciation, causing relative sea level to fall during infill. This paper explores stratigraphic architecture of fjord valley fills based on Late Quaternary deposition in Clyde Inlet, Baffin Island, Arctic Canada, as constrained by 11 cosmogenic dates and 9 accelerator mass spectrometry (AMS) 14 C datings. A major ice stream of the Laurentide Ice Sheet occupied Clyde Inlet at last glacial maximum and bulldozered through a U-shaped valley forming a lower sequence boundary. During the Early Holocene the system entered a deglacial stage; tidewater glaciers retreated rapidly (>100 km in 1000 yrs) through the fjord from 10.4 ka onward. Grounded ice lobes started retreating from the Clyde fjordhead by 9.4 ka. Then ice-contact fans (ICF) were deposited consisting of flat-topped fan deltas, covered with channels and boulder-strewn bars. Elevations of the surfaces vary between 62 and 77 m above sea level, which marks the relative sea level at the time of deposition and is considered to be the marine flooding surface. Marine muds have been draped directly onto the ICF complexes. Subsequently, coarse-grained glaciofluvial valley trains (GFVTs) prograde downstream caused by rapid base-level fall, despite possibly high sediment supply (i.e., forced regression). During the Late Holocene (3.5 ka) the last remaining lobes of the Laurentide Ice Sheet retreated from the middle parts of Clyde River basin to form the present Barnes Ice Cap. At this phase, the rate of base-level fall has decreased (~1.6 m/ka over the last 3.5 ka), still the river incises significantly, marking a reduced sediment supply. Narrow coarse sandy fluvial terraces were being deposited at the lowest level of the incised river valley. Clyde fjordhead may not have entered a postglacial stage by definition, nevertheless a strongly reduced sediment flux is apparent. Numerous upland lakes likely play a role in trapping sediment in the hinterland. In addition, we speculate that the glacial regime of the Barnes Ice Cap switched from a sediment producing regime to a nonerosive cold-based regime. In conclusion, stratigraphic patterns of valley fills in high-latitude areas display an evident signature of isostatic rebound and a strongly varying sediment supply. Rapid uplift causes ice proximal units to occur high in the infill and reverses classic fining upward valley fill sedimentary trends. The exact interplay of local sea-level change and sediment supply dictates the complexity of the valley fill, but coarsening upward trends with younger sandy fluvial deposits incising into the fill deposits ultimately have important implications for the interpretation of similar deglacial valley fill settings.

Abstract: This study investigates the Neogene strata of the AND-2A core recovered by the ANDRILL–Southern McMurdo Sound Project in the Victoria Land Basin, Antarctica, as an analog for assessing controls on reservoir quality in glacimarine deposits. The succession comprises a series of depositional sequences formed in marine environments within a failed rift under the influence of repeated advances and retreats of glacial ice, with attendant changes in sea level and sediment supply. Stratal cycles (sequences) typically follow a vertical succession from a basal diamictite deposited in ice-proximal settings fining upward into shoreface sandstone, muddy sandstone, and mudrock. The fining-upward sequence then coarsens upward into coastal and nearshore muddy sandstones and sandstones. Changes in paleoclimate mode through the Neogene caused variations in sequence development, including changes in sequence thickness, variety and range of facies, changes in the completeness of sequences, and changes in the proportion and character of diamictites. Results show that reservoir quality in glacimarine sandstone is dramatically affected by the presence of diagenetic carbonate precipitated during burial from connate cryogenic brine. Strong correlations exist between carbonate cement abundance, paleoclimate, and sequence stratigraphic systems tract. Sandstones that formed during the coldest (polar and subpolar) climate regimes have relatively low porosities (<15%) due to occlusion of pore space by carbonate cement. Decreased production and deposition of mud-sized material during the coldest climate conditions produced sequences characterized by higher overall permeability that were prone to infiltration by brine upon burial, leading to cementation. By contrast, the sandstones formed during relatively temperate climate regimes preserve higher porosities (25–45%) and lack significant cementation. Sequence stratigraphic relationships indicate that these porous sandstones are best developed in highstand delta systems that formed during ice minima. Individual sandstone bodies, which extend laterally over several kilometers, are enclosed by muddy lithologies. Porosity in these sandstones was retained as a result of discharge of dilute meltwater during deposition and subsequent isolation of sands between impermeable barriers. Trends identified in this study may prove useful in predicting and locating target reservoirs in other glaciogenic and glacimarine settings worldwide.

Abstract: Climate plays a significant role in determining the styles of depositional processes at different latitudes, which in turn influence the locations of hydrocarbon systems. Results of climate modeling may therefore provide important information for predicting the presence or absence of suitable hydrocarbon plays. To determine whether the models provide realistic results, the critical step is to validate the model results against proxy data where they are available. Paleoclimate proxy data are most often derived from more accessible low- to midlatitude regions and are biased towards warm climate states. However, general circulation models (GCMs) have traditionally been biased to colder temperatures, in particular at high-latitudes, struggling to maintain the high-latitude regions warm enough to sustain forests that were present during greenhouse periods, such as the mid-Cretaceous (~130–89 Ma), without exaggerated warming of the equatorial regions. To improve this approach, the HadCM3L coupled atmosphere–ocean GCM, a state-of-the-art model for the long simulations required to reach an equilibrium climate, was run for each stage of the Cretaceous using new paleogeographic base maps. Here, we compare the results for the Aptian (118.5 Ma) and Albian (105.8 Ma) with paleoclimate proxy data from the high northern latitudes in order to determine if the model produces viable results for this region. Paleoclimate analysis of fossil wood from conifer forests from Svalbard of Aptian–Albian age suggests that they grew in moist cool upland areas adjacent to warmer temperate lowland regions, probably with rivers and/or swamps present. Studies of conifers from the Canadian Arctic islands indicate that they grew under slightly cooler conditions than on Svalbard, similar to northern Canada today. The HadCM3L GCM results for Svalbard show that the dominant biome was evergreen taiga/montane forest with lowland temperate vegetation present during the Albian Stage, possibly with an element of deciduous taiga/montane forest in the Aptian (both cold boreal forests with short hot summers according to the Köppen–Geiger classification). The modeled mean annual temperature was ~−3.7° C at the sample sites, with summer temperatures rising to a mean of ~18° C during the Albian. Mean annual precipitation was ~571 mm. In the Canadian Arctic, the model results indicate that the biomes were more mixed than on Svalbard. The Aptian biome was dominantly deciduous taiga/montane forest with temperate vegetation in low-lying areas. The Albian landscape was dominated by evergreen taiga/montane forest, with some elements of deciduous taiga. Both stages were classified as cold boreal forest with short hot summers under the Köppen-Geiger classification scheme. Mean annual temperature was modeled to be ~−6.5° C at the sample sites, with summer temperatures reaching a mean of ~13° C, and mean annual precipitation was ~406 mm. These results suggest that the HadCM3L GCM, coupled with updated paleogeographic maps, can produce a good match to the climate proxy data in these difficult-to-model high-latitude areas.

Abstract: Criteria for recognizing a high-paleolatitude context for sedimentary successions are not widely established. Herein, we provide a facies analysis of the Permian succession of the high-paleolatitude Denison Trough in the southwestern Bowen Basin of Queensland, eastern Australia, and we use this analysis to highlight criteria that may be used to diagnose a high-paleolatitude context in this and other successions. A unified facies scheme for several formations, combining sedimentological and ichnological criteria, recognizes both deltaic and nondeltaic facies within the succession. Whereas a full array of deltaic facies is evident, ranging from distal prodelta to coastal plain, a more limited array of nondeltaic facies is recognized, ranging from shelfal to lower shoreface. The dominance of deltaic facies in the succession suggests that coastlines were overwhelmingly deltaic in aspect. The absence of middle and upper (nondeltaic) shoreface deposits suggests that shallow-water settings were constantly under physico–chemical stresses associated with deltaic efflux, and/or that such deposits were excised by transgressive ravinement following deposition. Deltas were mostly arcuate in planform, consistent with strong wave influence, although some show a more irregular or lobate plan morphology, suggesting significant fluvial influence. Four intervals within the Permian succession (coded P1 to P4) preserve evidence of formation under the direct or indirect (glaciomarine) influence of glacial ice. Palpable evidence of the high-paleolatitude context of the succession is preserved only in these intervals, most commonly in the form of dropstones, glendonite pseudomorphs after ikaite, gravel-grade clasts with modified shapes, and diamictites. In addition to vertical changes into and out of glacial intervals, paleolatitudinal changes in glacially influenced facies are evident across the 25- to 30-degree meridional transect from the Bowen Basin south to the Tasmanian Basin. Outside of glacial intervals P1 to P4, there are few sedimentological or ichnological indicators of high-paleolatitude deposition. Facies characteristics of deposition under glacial influence are therefore crucial to diagnosing the high-paleolatitudinal context of this and other successions.

Abstract: Climate plays an important role in controlling both the depositional and erosional settings. Tasmania provides spectacular outcrops where the rock record is well preserved and can be utilized to study the role of climate on sedimentation, especially, in the Late Cambrian and Early Ordovician. In this study a synthesis of field observation and mapping coupled with thin section analysis has been carried out to understand the climate control on the deposition of Late Cambrian–Early Ordovician siliciclastics which are exposed along the western and northwestern Tasmania, Australia. These siliciclastic sediments were deposited in syn-rift half grabens formed by Late Cambrian extension. The siliciclastics are mainly comprised of conglomerate, sandstone, and minor mudstone successions. Our analysis and interpretation suggest that these sediments were deposited in range of depositional settings. We have identified five broad facies that include sheet flows, braided fluvial, alluvial fans, intertidal and shallow marine environment. The stratigraphic build-ups of the study area suggest a strong influence of paleoclimate on the depositional processes. Globally, comparable sediments are different in term of depositional styles from their present day depositional analogues. This is principally due to different parameters controlling the overall depositional style, such as vegetation state, global sea level changes and climate conditions.

Abstract: In Bolivia, a marked climatic paleogradient (from west northwest to south) is visible in the Carboniferous depositional systems. In the northwest is the Pangean trend, a warm-water Pennsylvanian and Permian succession (preceded by a Late Devonian glacially derived rock assemblage). To the south is the cold climate Gondwanan trend, a succession of Late Devonian and Pennsylvanian cold-water siliciclastics with glacially influenced deposition. Whereas Devonian through (limited) Mississippian strata are comparable in overall character, a sharp climatic gradient in western South America is established by the earliest Pennsylvanian. The Pangean trend in northwestern Bolivia and Peru continues with warm-water Pennsylvanian and Permian carbonates, evaporites, and mixed siliciclastics of a semiarid, open seaway association (Copacabana Formation). This unit was deposited by marine transgression north (northern Bolivian subsurface and Lake Titicaca area), reaching central Bolivia by the Early Permian (Early Cisuralian). Regionally, the warm Pangean pattern continues into the younger and more restricted overlying Cisuralian and younger Permian and Triassic rocks characterized by restricted marine deposits of both humid and arid association (including red beds). To the south, Early Pennsylvanian rocks in the Gondwanan trend record continental and lacustrine glacial deposition as far north as central Bolivia, with glacial influence strongest in southern Bolivia and northern Argentina. By the Late Pennsylvanian, glacial influence has waned and is restricted to southern Bolivia near the Argentine border. The Copacabana Formation is enigmatic because of the following: (1) its autochthonous succession over cold-water, glaciogenic deposits of the Late Devonian and Mississippian and (2) its apparent coeval deposition with Pennsylvanian (and Permian) glacial diamictites. Although the former can be attributed to paleolatitudinal shift, or a clockwise rotation of Gondwana, what is not easily explained (and much discussed) is the autochthonous continuity of northeastern and central Bolivian carbonate deposits of the northern Peru–Bolivia Basin with southern Pennsylvanian and Permian glaciogenic deposits, which accumulated in the Tarija–Chaco Basin. Given that these cold and warm-water deposits were coeval in time, a severe climate gradient must have existed across Bolivia beginning in Pennsylvanian time. Western Gondwana records steady movement from high latitudes (~55°S) in the Late Devonian to midlatitudes (~40°S) by Pennsylvanian time. Glacial deposits seen in the northwest during the Late Devonian become restricted to the southern Tarija–Chaco Basin by the Late Pennsylvanian. By Early Pennsylvanian (Bashkirian) time, carbonates, evaporites, and siliciclastics were deposited in northwest Bolivia. In central Bolivia, Mississippian diamictites, undated Pennsylvanian siliciclastics, Copacabana lithofacies, and carbonates of the Vitiacua Formation are vertically stacked at a few locations.