Early-to-mid Miocene erosion rates inferred from pre-Dead Sea rift Hazeva River fluvial chert pebbles using cosmogenic <sup>21</sup>Ne
<p>In this work, we utilize a novel application of cosmogenic <span class="inline-formula"><sup>21</sup>Ne</span> measurements in chert to compare exposure times measured in eroding surfaces in the central Jordanian Plateau with exposure times from chert pebbl...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-04-01
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| Series: | Earth Surface Dynamics |
| Online Access: | https://www.earth-surf-dynam.net/8/289/2020/esurf-8-289-2020.pdf |
| Summary: | <p>In this work, we utilize a novel application of cosmogenic <span class="inline-formula"><sup>21</sup>Ne</span> measurements in chert to compare exposure times measured in eroding surfaces in the central Jordanian Plateau with exposure times from chert pebbles transported by the Miocene Hazeva River. The Miocene Hazeva River was a large fluvial system (estimated catchment size <span class="inline-formula">></span> 100 000 km<span class="inline-formula"><sup>2</sup></span>) that drained the Arabian Plateau and Sinai Peninsula into the Mediterranean Sea during the early-to-mid Miocene. It was established after the rifting of the Red Sea uplifted the Arabian Plateau during the Oligocene. Following late-Miocene-to-early-Pliocene subsidence along the Dead Sea rift, the Hazeva drainage system was abandoned and dissected, resulting in new drainage divides on either side of the rift. We find modern erosion rates derived from cosmogenic <span class="inline-formula"><sup>21</sup>Ne</span>, <span class="inline-formula"><sup>26</sup>Al</span>, and <span class="inline-formula"><sup>10</sup>Be</span> in exposed in situ chert nodules to be extremely slow (between 2–4 mm kyr<span class="inline-formula"><sup>−1</sup></span>). Comparison between modern and paleo-erosion rates, measured in chert pebbles, is not straightforward, as cosmogenic <span class="inline-formula"><sup>21</sup>Ne</span> was acquired partly during bedrock erosion and partly during transport of these pebbles in the Hazeva River. However, <span class="inline-formula"><sup>21</sup>Ne</span> exposure times calculated in Miocene cherts
are generally shorter (ranging between <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mn mathvariant="normal">0</mn><mrow><mo>-</mo><mn mathvariant="normal">0</mn></mrow><mrow><mo>+</mo><mn mathvariant="normal">59</mn></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="23pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="c57f2577aded925cc9eeb50bfe158236"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="esurf-8-289-2020-ie00001.svg" width="23pt" height="17pt" src="esurf-8-289-2020-ie00001.png"/></svg:svg></span></span> and <span class="inline-formula">242±113</span> kyr) compared to exposure times calculated in the currently eroding chert nodules presented here (<span class="inline-formula">269±49</span> and <span class="inline-formula">378±76</span> kyr) and other chert
surfaces currently eroding in hyperarid environments. Miocene exposure times are shorter even when considering that they account for bedrock erosion in addition to maintained transport along this large river. Shorter exposure times in Miocene cherts correspond to faster paleo-erosion rates, which we attribute to a combination of continuous surface uplift and significantly wetter climatic conditions during the early-to-mid Miocene.</p> |
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| ISSN: | 2196-6311 2196-632X |