Global Aridity during the Early Miocene? A Terrestrial Paleoclimate Record from the Ebro Basin, Spain

Hamer, Jessica M. M.; Sheldon, Nathan D.; Nichols, Gary

doi:10.1086/519780

Cited by 32 publications

(14 citation statements)

References 21 publications

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“…Smith et al ., , ), this and other well‐developed and widespread palaeocatenas throughout the stratigraphic section (Hyland & Sheldon, ) also indicate at least periodic stability within the broader setting of a large distributive fluvial system (e.g. Hamer et al ., ; Weissmann et al ., ; Smith et al ., ). This finding is congruent with the concept that sedimentary processes within large continental basins like the GRB may exhibit cyclical, and perhaps orbitally forced (Hamer et al ., ; Abels et al ., ; Smith et al ., ), patterns of stability/instability on long timescales, particularly during periods characterized by extreme climate conditions (e.g.…”

Section: Discussionmentioning

confidence: 97%

“…Hamer et al ., ; Weissmann et al ., ; Smith et al ., ). This finding is congruent with the concept that sedimentary processes within large continental basins like the GRB may exhibit cyclical, and perhaps orbitally forced (Hamer et al ., ; Abels et al ., ; Smith et al ., ), patterns of stability/instability on long timescales, particularly during periods characterized by extreme climate conditions (e.g. Foreman et al ., ; Smith et al ., ).…”

Section: Discussionmentioning

confidence: 99%

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Examining the spatial consistency of palaeosol proxies: Implications for palaeoclimatic and palaeoenvironmental reconstructions in terrestrial sedimentary basins

Hyland

Sheldon

2016

Sedimentology

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Terrestrial sediments are a significant archive of past conditions, and the 'critical zone' in particular is important for understanding past and ongoing interactions between the atmosphere, biosphere and lithosphere. Understanding the details of a palaeolandscape or palaeocatena record can greatly improve palaeoenvironmental descriptions and palaeoclimate reconstructions during crucial time periods in the past. This article presents multi-proxy data including palaeosol descriptions, major element geochemistry, magnetic composition and stable isotope geochemistry from an early Eocene palaeosol transect, which show distinct trends in palaeosol features and geochemistry across the landscape, particularly in terms of the differences between A-horizon and B-horizon samples. A-horizon geochemical and physical features are highly variable and reflect other not strictly pedogenic controls, whereas Bhorizon composition is extremely consistent. Given that most palaeoclimatic or palaeoenvironmental proxies based on palaeosols use B-horizon features, these results highlight the robustness of those proxies. At the same time, the difference between A-horizons and B-horizons and the variability within Ahorizons of the same palaeosol in different geomorphic settings underscores the importance of palaeosol description, detailed sampling, and a multiproxy approach to produce both precise and accurate reconstructions of past environments and climates using terrestrial sedimentary records.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Examining the spatial consistency of palaeosol proxies: Implications for palaeoclimatic and palaeoenvironmental reconstructions in terrestrial sedimentary basins

Hyland

Sheldon

2016

Sedimentology

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“…Global climate in the Miocene is thought to be relatively warm and arid, peaking with the middle Miocene climatic optimum [Zachos et al, 2001]. However, recent investigations into the major element geochemistry of early Miocene paleosols from the north central Ebro Basin suggest that the regional climate was subhumid to humid, with considerably more precipitation than the earlier arid to semiarid climate during the late Oligocene [Cabrera et al, 2002;Hamer et al, 2007]. Uplift of the western Pyrenees by 30 Ma suggests that significant topography existed across the entire range [Whitchurch et al, 2011].…”

Section: Spatiotemporal Patterns Of Synorogenic Exhumationmentioning

confidence: 99%

Exhumation of the southern Pyrenean fold‐thrust belt (Spain) from orogenic growth to decay

et al. 2013

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[1] The deformation and exhumation history of an orogen reflects the interactions between tectonic and surface processes. We investigate orogenic wedge deformation, erosion, and sedimentation in the Pyrenees by (a) quantifying the spatiotemporal patterns of exhumation across the southern fold-thrust belt (FTB) with bedrock apatite fission track (AFT) thermochronology and (b) comparing the results with existing deformation, exhumation, and sedimentation chronologies. Eighteen new samples record exhumation during and after orogenesis between 90 and 10 Ma. Rocks from the range core (Axial Zone) record rapid exhumation that progresses east to west and north to south, consistent with patterns of tectonically driven uplift. Synorogenic sediments shed into piggyback basins on the southern fold-thrust belt during mountain building retain a detrital exhumation signal from the Axial Zone. In contrast, samples from other structural positions record exhumation of the thin-skinned Pyrenean thrust sheets, suggesting sediment burial and heating of sufficient magnitudes to reset the AFT system (>~3 km). In some locations, exhumation of these fold-thrust structures is likely an erosional response to thrust-driven rock uplift. We identify an exhumation phase~25-20 Ma that occurs along the central and eastern Spanish Pyrenees at the boundary between thick-and thin-skinned portions of the wedge. We suggest that this distributed exhumation event records (a) a taper response in the southern orogenic wedge to sediment loading and/or (b) a shift to wetter, stormier climate conditions following convergence-driven uplift and full topographic development. A final exhumation phase between~20 and 10 Ma may record the excavation of the southern fold-thrust system following base level lowering in the Ebro Basin.Citation: Rushlow, C. R., J. B. Barnes, T. A. Ehlers, and J. Verge´s (2013), Exhumation of the southern Pyrenean fold-thrust belt (Spain) from orogenic growth to decay, Tectonics, 32, 843-860,

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“…The palaeoclimate in the Ebro Basin in the Early Miocene has been determined to be temperate on the basis of climatic proxies calculated from chemical analyses on palaeosol profiles (Hamer et al ., ). Although minor variations are recognized in estimates for mean annual temperature and precipitation, there is no clear signal of significant changes in climate conditions during the early Miocene (Hamer et al ., ).…”

Section: Examples From the Ebro Foreland Basin (Palaeogene–neogene Smentioning

confidence: 97%

Autogenic dynamics of alluvial fans in endorheic basins: Outcrop examples and stratigraphic significance

Ventra

Nichols

2013

Sedimentology

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Alluvial fans are relatively simple depositional systems, due to the direct coupling of sediment sources and adjacent accumulation areas. Nonetheless, general models of alluvial-fan evolution and stratigraphy remain elusive, due to the great sensitivity of such systems to allogenic controls and their strongly case-specific responses. Autogenic processes intrinsic to alluvial-fan dynamics can complicate stratigraphic architectures, with effects not easily distinguishable from those of allogenic forcing. A distinction is made here between lateral autogenic dynamics, tied to spatial sediment distribution over fan surfaces, and vertical autogenic dynamics, related to independent incision-aggradation cycles. Autogenic mechanisms have been highlighted recently by modelling studies, but remain poorly constrained in field-based studies. Examples are presented here from the margins of the Cenozoic Teruel and Ebro basins (Spain), where alluvial fans accumulated thick successions during phases of basin topographic closure and endorheic drainage which promoted forced aggradation. Fan successions consist of conformable architectures of stacked clastic sheets, laterally continuous and with no evidence of internal unconformities, inset architectures, fan segmentation or preserved incised channels. Continuous aggradation in these closed basins strongly inhibited 'vertical' autogenic dynamics in the form of fan head and through fan incision, due to the forced rise in geomorphic base level and the creation of positive accommodation. Furthermore, the lack of incised channels favoured widespread sediment transport and aggradation over broad fan sectors in relatively short time spans, in contrast to the typical occurrence of active lobes and abandoned fan surfaces caused by 'lateral' autogenic dynamics. Stratigraphic records of alluvial fans developed in endorheic basins are essentially complete and largely unaffected by autogenic processes. The latter characteristic implies that they can be more unambiguously interpreted in terms of allogenic forcing, because stratigraphic signatures are not complicated by the effects of complex fan autodynamics.

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Global Aridity during the Early Miocene? A Terrestrial Paleoclimate Record from the Ebro Basin, Spain

Cited by 32 publications

References 21 publications

Examining the spatial consistency of palaeosol proxies: Implications for palaeoclimatic and palaeoenvironmental reconstructions in terrestrial sedimentary basins

Examining the spatial consistency of palaeosol proxies: Implications for palaeoclimatic and palaeoenvironmental reconstructions in terrestrial sedimentary basins

Exhumation of the southern Pyrenean fold‐thrust belt (Spain) from orogenic growth to decay

Autogenic dynamics of alluvial fans in endorheic basins: Outcrop examples and stratigraphic significance

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