Karst subsidence as a control on the accumulation and preservation of aeolian deposits: A Pleistocene example from a proglacial outwash setting, Ebro Basin, Spain

Abstract

Meltwater flows emanating from the Pyrenees during the Pleistocene constructed a braided outwash plain in the Ebro Basin and led to the karstification of the Neogene gypsum bedrock. Synsedimentary evaporite dissolution locally increased subsidence rates and generated dolines and collapses that enabled the accumulation and preservation of outwash gravels and associated windblown deposits that were protected from erosion by later meltwater flows. In these localized depocentres, maximum rates of wind deceleration resulted from airflow expansion, enabling the accumulation of cross‐stratified sets of aeolian strata climbing at steep angles and thereby preserving up to 5 m thick sets. The outwash plain was characterized by longitudinal and transverse fluvial gravel bars, channels and windblown facies organized into aeolian sand sheets, transverse and complex aeolian dunes, and loess accumulations. Flat‐lying aeolian deposits merge laterally to partly deformed aeolian deposits encased in dolines and collapses. Synsedimentary evaporite dissolution caused gravels and aeolian sand deposits to subside, such that formerly near‐horizontal strata became inclined and generated multiple internal angular unconformities. During episodes when the wind was undersaturated with respect to its potential sand transporting capacity, deflation occurred over the outwash plain and coarse‐grained lags with ventifacts developed. Subsequent high‐energy flows episodically reached the aeolian dune field, leading to dune destruction and the generation of hyperconcentrated flow deposits composed in part of reworked aeolian sands. Lacustrine deposits in the distal part of the outwash plain preserve rhythmically laminated lutites and associated Gilbert‐type gravel deltas, which developed when fluvial streams reached proglacial lakes. This study documents the first evidence of an extensive Pleistocene proglacial aeolian dune field located in the Ebro Basin (41˙50° N), south of what has hitherto been considered to be the southern boundary of Pleistocene aeolian deposits in Europe. A non‐conventional mechanism (evaporite karst‐related subsidence) for the preservation of aeolian sands in the stratigraphic record is proposed.

Response of fluvial, aeolian, and lacustrine systems to late Pleistocene to Holocene climate change, Lower Moravian Basin, Czech Republic

“…The inverted OSL ages are best reconciled as representing an unroofing process, in which strata were slumped and transported en masse without bleaching from sunlight. Fluvial undercutting and subsequent slumping of aeolian strata, which gives rise to sandy sedimentgravity flows composed of aeolian (mostly) and fluvial sediments (c.f., Luzón et al, 2012), substantially explain the nature of the deposits. However, reconciling the lack of subsequent current reworking and sunlight bleaching of the deposits with a braided stream environment is difficult.…”

Some evolutionary patterns of palaeokarst developed in Pleistocene deposits (Ebro Basin, NE Spain): Improving geohazard awareness in present‐day karst

“…The Pleistocene succession is dominated by fluvial gravels, but other deposits such as aeolian sands, loess, alluvial breccias, or lacustrine mudstones also occur (Gil, Luzón, et al, ; Luzón et al, ) evidencing a complex paleogeographical framework (Figure ), although a southeast‐flowing fluvial system with braided channels and gravel bars dominated the scenery (Luzón et al, ). In the alluvial plain, small lakes locally developed in subsiding karst areas (Luzón et al, ), where small deltas grew when reached by flooding (Luzón et al, ; Pueyo‐Anchuela et al, ).…”

“…In the alluvial plain, small lakes locally developed in subsiding karst areas (Luzón et al, ), where small deltas grew when reached by flooding (Luzón et al, ; Pueyo‐Anchuela et al, ). During episodes of low availability of water, alluvial plains were exposed, acting as source of sand for dunes generation (Luzón et al, ); the wind pattern was quite similar to the recent one and alluvial fans, fed in the nearby reliefs made on Neogene rocks, prograded (Gil, Luzón, et al, ).…”

“…The age of the affected deposits ranges from Early to Late Pleistocene (Julián Andrés & Chueca Cía, 1998; Gil et al, ; Gil Marín, Esnaola Gómez, Marqués, & Herranz, ; Marqués, Santos, Esnaola, & Gil, ; Soriano et al, ). Research on palaeokarst in this area has been focused on studying the influence of karst on sedimentation, application to develop a genetic classification of present dolines, comparison of karst effects in sediments with other processes, such as diapirism or tectonics, and so forth (Benito, Pérez‐González, Gutierrez, & Machado, ; Benito, Sancho, Peña, Machado, & Rhodes, ; Gil, Luzón, et al, ; Gutiérrez et al, ; Gutiérrez, Parise, de Waele, & Jourde, ; Luzón, Pérez, Soriano, & Pocoví, ; Luzón et al, ; Simón et al, ). In addition, mantled karst is still today's one of the main geological processes observed in this region.…”

Reconstruction of three-dimensional eolian dune architecture from one-dimensional core data through adoption of analog data from outcrop

“…Although several alternative mechanisms for the accumulation and preservation of sets of eolian strata have been proposed, including the infilling of localized accommodation space (e.g., Langford et al, 2008;Luzón et al, 2012), accumulation around relic eolian topography (Fryberger, 1986), and exceptional bedform preservation following rapid inundation by water or lava flows (e.g., Glennie and Buller, 1983;Mountney et al, 1999;Benan and Kocurek, 2000), the bedform climbing mechanism remains a convincing explanation for the origin of the majority of ancient preserved eolian dune successions (Mountney, 2012).…”