DOI

10.17077/etd.25rc5gg2

Document Type

Thesis

Date of Degree

Spring 2017

Degree Name

MS (Master of Science)

Degree In

Geoscience

First Advisor

Ukstins Peate, Ingrid

First Committee Member

Bettis, Art

Second Committee Member

Riishuus, Morten S.

Third Committee Member

Yingst, R. Aileen

Abstract

Basalts from Askja, Iceland have high MgO (5-18 wt %) and high Fe2O3 (5-18 wt %: Baratoux et al., 2011; Mangold et al., 2013, this study) similar to Martian basalts, which have Fe2O3 from 10-33 wt % McSween et al, 2006; Ming et al., 2008]) and MgO around 11 wt. % (McSween et al., 2009). Askja’s cold desert climate provides a good weathering analogueanalog (Mountney and Russell, 2004). Askja is located in the Northern Volcanic Zone of Iceland and basalts have been weathered to form mafic volcaniclastic deposits in a 40-km long sand sheet to the E-SE of the Askja caldera complex (Fig. 1; (Kuritani et al., 2011). The 2014-2015 Holuhraun eruption was emplaced onto the southeastern part of the sand sheet (Fig. 1) and altered the regional geomorphology and may have impacted the geochemistry of the sand sheet itself by addition of wind-blown ash and crystals, plus weathering of the lava flow (MgO content of ~7.1 wt % Geiger et al., 2016). Mangold et al. (2011) found that Icelandic sands show little chemical variations but that study was limited in the number of samples (12 sand samples and 12 rock seven rock, seven sand; Mangold et al., 2011). Here we expand on that study and we have created a morphological and geochemical database with the goal of identifying relevant trends to past and present Martian environments.

The Askja sand sheet, between ~10 cm and ~10 m thick, covers 240 km2 (Mountney and Russell). Mountney and Russell described three distinct sections of the sand sheet. The southwest section is deflationary and defined by very fine to medium grained basaltic sand with cobbles and boulders of lithologies sourced from adjacent to and distal from the sand sheet. The central part is inflating and is dominated by very fine-grained sand, relict lava fields, and small to large sand ripples. The northeast portion is also inflating but that accumulation is limited to topographic depressions. The northeast, characterized by sand mostly composed of pumice from the 1875 Askja eruption and basalt clasts from local lava fields, was not studied in detail here due to the difference in chemistry. Martian basaltic eolian sediments may record a long history of local and global climate change and they may have been potential habitats where water, nutrients and organic carbon mixed below the surface (Blake et al., 2013; Fisk et al., 2013). Basaltic sand fields on Earth have not been characterized as well as felsic sands, but represent a unique analog to deposits such as the Stimson Fm. on Mars (Mangold et al., 2011; Banham et al., 2016; Gupta et al., 2016; Ming et al., 2016; Newsom et al., 2016; Yen et al., 2016) . Eolian dominated weathering prevalent at Askja volcano, Iceland, likely also occurred on Mars and Askja mafic volcaniclastic dunes could be the best morphological and compositional analogueanalog for Martian eolian dunes (Edgett and Lancaster, 1993).

Public Abstract

The Dyngjusandur sand sheet in the Central Highlands of Iceland is composed of wind-deposited black sand of similar composition to that of the Martian crust. The sand includes 80-90% volcanic glass grains with basaltic minerals, olivine, pyroxene and plagioclase making up the remaining 10-20%. The glass and minerals originated from volcanic eruptions in the Northern Volcanic Zone of Iceland, many of these eruptions interacting with glaciers, resulting in the formation of glass-rich hyaloclastite ridges. The volcanic material in this area is of similar composition, in terms of magnesium oxide and iron-oxide, to Martian volcanics. Ice, water and wind breakdown these ridges and local lava flows to create the sand grains that compose Dyngjusandur sand sheet. Many of these materials are deposited in a glacier flood plain at the southwestern edge of the sand sheet before being transported via wind towards the northeast across Dyngjusandur. Trenches dug in the sand sheet have revealed complicated structures in the sand suggesting recent and long-term activity.

The Stimson Fm. in Gale Crater, Mars has been classified as wind-deposited basaltic sandstone with a similar composition to the Martian crust. Much like Dyngjusandur in Iceland, displays complex structural features suggesting a long-term history of deposition. By creating a chemical and morphological database of Dyngjusandur sand sheet this study will argue that Dyngjusandur is a compositional and structural analog for the Stimson Fm. in Gale Crater, Mars.

Keywords

Dyngjusandur, Iceland, mafic, Mars, sand, Stimson

Pages

xii, 145 pages

Bibliography

Includes bibliographical references (pages 54-57).

Comments

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Copyright

Copyright © 2017 Michael James Sara

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