Desert pavement-coated surfaces in extreme deserts present the longest-lived landforms on Earth

Abstract

All exposed rocks on Earth's surface experience erosion; the fastest rates are documented in rapidly uplifted monsoonal mountain ranges, and the slowest occur in extreme cold or warm deserts-millennial submeterscale erosion may be approached only in the latter. The oldest previously reported exposure ages are from boulders and clasts of resistant lithologies lying at the surface, and the slowest reported erosion rates are derived from bedrock outcrops or boulders that erode more slowly than their surroundings; thus, these oldest reported ages and slowest erosion rates relate to outstanding features in the landscape, while the surrounding landscape may erode faster and be younger. We present erosion rate and exposure age data from the Paran Plains, a typical environment in the Near East where vast abandoned alluvial sur-faces (10 2 -10 4 km 2 ) are covered by well-developed desert pavements. These surfaces may experience erosion rates that are slower than those documented elsewhere on our planet and can retain their original geometry for more than 2 m.y. Major factors that reduce erosion converge in these regions: extreme hyperaridity, tectonic stability, fl at and horizontal surfaces (i.e., no relief), and effective surface armoring by a clast mosaic of highly resistant lithology. The 10 Be concentrations in amalgamated desert pavement chert clasts collected from abandoned alluvial surfaces in the southern Negev, Israel (representing the Sahara-Arabia Deserts), indicate simple exposure ages of 1.5-1.8 Ma or correspond to maximum erosion rates of 0.25-0.3 m m.y. -1 . The 36 Cl in carbonate clasts, from the same pavement, weathers faster than the chert and yields simple exposure ages of 430-490 ka or maximum erosion rates of 0.7-0.8 m m.y. -1 . These ages and rates are exceptional because they represent an extensive landform. The 10 Be concentrations from samples collected at depth and optically stimulated luminescence (OSL) dating reveal a two-stage colluvial deposition history followed by eolian addition of 40 cm of silt during the past 170 k.y. Our results highlight the effi ciency of desert pavement armor in protecting rocks from erosion and preserving such geomorphic surfaces for millions of years.

Total vertical sediment flux and PM10 emissions from disturbed Chihuahuan Desert surfaces

“…In the absence of vegetation, desert pavements form as clasts are lifted to the surface by clays undergoing changes in hydration. This roughened surface encourages further deposition of wind-borne fine sediments (Pelletier et al, 2007;Matmon et al, 2009;Dietze et al, 2016) resulting in older surfaces with more clay and silt from aeolian accretion (Meadows et al, 2006). Periodic surface disturbances can heal in a matter of years if the clasts remain (Wainright et al, 1999) or decades if the clasts are completely removed (Haff and Werner, 1996;Pelletier et al, 2007).…”

Dating desert pavements – First results from a challenging environmental archive

“…Anderson et al (2002), Wells et al (1995) and McFadden et al (1998) applied thermoluminescence dating (TL) on desert pavements in the Mojave desert, USA, while Matmon et al (2009) used optically stimulated luminescence dating (OSL) for their investigations in the Negev desert of southern Israel. However, in all of these studies, the dating results are presented, but no details about the luminescence characteristics are given and discussed.…”

“…However, Dietze et al (2011) demonstrate that these relative age indicators are problematic, because there is no direct relationship between the surface properties, soil development and the age of desert pavements. Numerical dating of the clasts of desert pavements using cosmogenic 3 He and 10 Be surface exposure dating was e. g. applied by Wells et al (1995) and Matmon et al (2009), with a focus on dating the beginning of desert pavement formation and investigating their surface stability over time. However, the process of dust trapping and therefore the dating of the eolian fines below the desert pavement can best be dated by luminescence dating techniques (Aitken, 1985).…”

El Palimpsesto Como Una Puerta De Acceso a Diferentes Temporalidades: El Caso De Río Las Salinas 2 (Tucumán, Argentina)

“…En estos casos, la distribución de las pátinas en las caras de los artefactos, sumada a los eventos de talla in situ, son indicadores de que la superficie de glacis sobre las que yacen los conjuntos líticos es una geoforma estable (Adelsberger y Smith 2009). Esto es esperable en pavimentos maduros, entendidos como superficies de larga vida (Matmon et al 2009;Aldersberger et al 2013).…”