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Gold Prospecting
Alluvial Gold Prospecting
Confused about sudden change in deposition layers in creek
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<blockquote data-quote="user 4386" data-source="post: 481168" data-attributes="member: 4386"><p>I suspect that BE means a Bendigonian age graptolite locality, and that BECH is a locality that straddles the Bendigonian and Chewtonian age boundary (or possibly that the fossil cannot be uniquely assigned to one or the other, but could be either). Rocks of Ordovician age in Victoria are subdivided into zones according to their graptolite species - we don't know exact ages, but we do know that a certain graptolite fossil occurs before (or after) another species, In a general way, the graptolites evolved to be simpler in form at younger ages. They are named after areas where they are abundant - so from oldest to youngest in rocks of Ordovician age they are the Lancefieldian, Bendigonian, Chewtonian, Castlemainian, Yapeenian, Darriwilian, Gisbornian, Eastonian and Bolindian. So in your area they are fairly old Ordovian (we would actually say "low in the Ordovician sequence" since it really represents their position in the stratigraphy rather than age, although the position correlates with age). The graptolites did not stop at the top of the Ordovician (Bolindian) but continued into overlying (and younger) Silurian and Devonian rocks - by the Devonian a single stipe ("arm") was common (Monograptus) whereas low in the Ordovician forms with 8, 4 and 2 stipes were common.</p><p></p><p><img src="https://www.prospectingaustralia.com/forum/img/member-images/4386/1554105293_graptolites.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p><img src="https://www.prospectingaustralia.com/forum/img/member-images/4386/1554105362_graptolites2.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p><img src="https://www.prospectingaustralia.com/forum/img/member-images/4386/1554105362_graptolites3.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p><img src="https://www.prospectingaustralia.com/forum/img/member-images/4386/1554105470_graptolites4.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p></blockquote><p></p>
[QUOTE="user 4386, post: 481168, member: 4386"] I suspect that BE means a Bendigonian age graptolite locality, and that BECH is a locality that straddles the Bendigonian and Chewtonian age boundary (or possibly that the fossil cannot be uniquely assigned to one or the other, but could be either). Rocks of Ordovician age in Victoria are subdivided into zones according to their graptolite species - we don't know exact ages, but we do know that a certain graptolite fossil occurs before (or after) another species, In a general way, the graptolites evolved to be simpler in form at younger ages. They are named after areas where they are abundant - so from oldest to youngest in rocks of Ordovician age they are the Lancefieldian, Bendigonian, Chewtonian, Castlemainian, Yapeenian, Darriwilian, Gisbornian, Eastonian and Bolindian. So in your area they are fairly old Ordovian (we would actually say "low in the Ordovician sequence" since it really represents their position in the stratigraphy rather than age, although the position correlates with age). The graptolites did not stop at the top of the Ordovician (Bolindian) but continued into overlying (and younger) Silurian and Devonian rocks - by the Devonian a single stipe ("arm") was common (Monograptus) whereas low in the Ordovician forms with 8, 4 and 2 stipes were common. [img]https://www.prospectingaustralia.com/forum/img/member-images/4386/1554105293_graptolites.jpg[/img] [img]https://www.prospectingaustralia.com/forum/img/member-images/4386/1554105362_graptolites2.jpg[/img] [img]https://www.prospectingaustralia.com/forum/img/member-images/4386/1554105362_graptolites3.jpg[/img] [img]https://www.prospectingaustralia.com/forum/img/member-images/4386/1554105470_graptolites4.jpg[/img] [/QUOTE]
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Gold Prospecting
Alluvial Gold Prospecting
Confused about sudden change in deposition layers in creek
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