Episodic Late Holocene dune movements on the sand-sheet area, Great Sand Dunes National Park and Preserve, San Luis Valley, Colorado, USA

Abstract

The Great Sand Dunes National Park and Preserve (GSDNPP) in the San Luis Valley, Colorado, contains a variety of eolian landforms that reflect Holocene drought variability. The most spectacular is a dune mass banked against the Sangre de Cristo Mountains, which is fronted by an extensive sand sheet with stabilized parabolic dunes. Stratigraphic exposures of parabolic dunes and associated luminescence dating of quartz grains by single-aliquot regeneration (SAR) protocols indicate eolian deposition of unknown magnitude occurred ca. 1290–940, 715 ± 80, 320 ± 30, and 200–120 yr ago and in the 20th century. There are 11 drought intervals inferred from the tree-ring record in the past 1300 yr at GSDNPP potentially associated with dune movement, though only five eolian depositional events are currently recognized in the stratigraphic record. There is evidence for eolian transport associated with dune movement in the 13th century, which may coincide with the “Great Drought”, a 26-yr-long dry interval identified in the tree ring record, and associated with migration of Anasazi people from the Four Corners areas to wetter areas in southern New Mexico. This nascent chronology indicates that the transport of eolian sand across San Luis Valley was episodic in the late Holocene with appreciable dune migration in the 8th, 10–13th, and 19th centuries, which ultimately nourished the dune mass against the Sangre de Cristo Mountains.

Optically stimulated luminescence dating of young sediments: A review

“…This young deposit had an OSL age of 36 ± 5 years, giving confidence that this material was well-bleached at deposition. The same presumably applies to the 25 ± 4 years reported by Stokes et al (2004), the 20 ± 2 years reported by Forman et al (2006) and the 10 ±3 years reported by Bristow et al (2007) (see footnote to Table 2). In the first case, the sample was taken at a depth of 70 cm in Mahelian Sahel, in the second, it was aeolian sand sampled near the surface in San Luis Valley, Colorado, USA, and in the third, it was aeolian sand sampled at the surface of a dune in the Namib dessert.…”

“…Five aeolian depositional events in the past ∼ 1200 years were found in the Great Sand Dunes National Park and Preserve in the San Luis Valley, Colorado by Forman et al (2006). The primary geochronometer was SAR quartz OSL dating (using a 200°C preheat temperature), with Multiple-Aliquot Regeneration (MAR) as a complementary approach (Singhvi et al, 1982;Jain et al, 2003) using sand-sized quartz.…”

“…6. The frequency distribution of OSL ages (shown at 2 sigma) of aeolian deposition (Forman et al, 2006) from the Great Sand Dunes National Park and Preserve, Colorado is plotted together with the rainfall record and the Palmer Drought Severity Index (PDSI) inferred from the tree-ring time series.…”

“…c Using thermal transfer correction. dStokes et al (2004) reported an OSL age of 25 ± 4 years for a sample taken from ∼70 cm depth in a dune deposit in the Malian Sahel,Forman et al (2006) reported an OSL age of 20 ±2 years for a sample recovered near the surface in a dune deposit in San Luis Valley, Colorado, USA and Bristow et al…”

Late Holocene dune migration on the south Texas sand sheet

“…3b and c), that may be coincident with episodes of dune reactivation (cf. Marin et al, 2005;Forman et al, 2006Forman et al, , 2008. The PDSI includes parameterization for precipitation, temperature and also incorporates a supply and demand model for soil moisture.…”