Dublin Core for stratigraphic units

This is a first draft which shows how I would encode metadata on stratigraphic units.
The usage of the coverage and subject (which both now contain the chronostratigraphic position of the unit) tag is still preliminary. I have to look up the DC specifications, as far as I remember there was the possibility to specify spatial as well as temporal coverage..

<metadata>
<oai_dc:dc xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
<dc:format>text/html</dc:format>
<dc:rights>
Licensed under a Creative Commons Attribution 2.5 License
</dc:rights>
<dc:publisher>
Stratigraphy.Net http://www.stratigraphy.net</dc:publisher>
<dc:type>Stratigraphic Unit</dc:type>
<dc:title>Ammergauer Schichten</dc:title>
<dc:date>1855</dc:date>
<dc:creator>Studer</dc:creator>
<dc:identifier>http://some_URL</dc:identifier>
<dc:relation>Wetzstein-Schichten</dc:relation>
<dc:subject>Malm</dc:subject>
<dc:coverage>Malm</dc:coverage>
<dc:coverage>Germany</dc:coverage>
<dc:coverage>Ammergebirge</dc:coverage>
</oai_dc:dc>
</metadata>