Wrangellian Posted October 21, 2014 Share Posted October 21, 2014 (edited) Gerastos is found in many different localities and formations in Morocco. There are many different species, too! Well, different... it's all in the details with Gerastos On a side note, the so-called "Hamar Lagdad formation" does not exist. It's maybe a fancy term invented by traders in order to make it seem as though they provide your with the precise origin of the trilobite. Hamar Lagdad is a valid locality east of Erfoud, with a carbonate mud mound facies. But no formation. OK so at least I have a location, but what is the name of the formation in that area, or are there several? Edited October 21, 2014 by Wrangellian Link to comment Share on other sites More sharing options...
piranha Posted October 22, 2014 Share Posted October 22, 2014 On 10/21/2014 at 3:02 PM, Wrangellian said: OK so at least I have a location, but what is the name of the formation in that area, or are there several? Attached is a chart with maps to help pinpoint the different species of Gerastos and their formations in Morocco: Gibb, S.L., & Chatterton, B.D.E. (2010) Gerastos (Order Proetida; Class Trilobita) from the Lower to Middle Devonian of the southern Moroccan Anti-Atlas region. Palaeontographica Canadiana, 30:1-89 2 Link to comment Share on other sites More sharing options...
Wrangellian Posted October 22, 2014 Share Posted October 22, 2014 Thanks again Scott, I guess I need to narrow down my specimen to species to be able to narrow down the locations... The only info that came with it is "Proetus sp, Devonian, Morocco, Collector: BHI" Link to comment Share on other sites More sharing options...
Fred Posted October 22, 2014 Share Posted October 22, 2014 OK so at least I have a location, but what is the name of the formation in that area, or are there several? Unfortunately to my experience, a specimen from there labeled as coming from the 'Hamar Lagdad fm', does not necesserily originate from the Hamar Lagdad hill range (which is, by the way, not depicted on the maps in the Gibb & Chatterton publication because it is more to the northeast). It might well be that your specimen is found in the Ma'der basin altogether. Imho, your best bet it to identify the specimen. This will give you a fair idea of the stratigraphy, because most Gerastos are more or less confined to a specific formation. You might even be tempted to derive a a shortlist of potential localities from literature. However, since this one is clearly a surface find, it might have been collected outside of the usual spots, maybe even in colluvium. Perhaps even an accidental find when crossing the landscape. I think it is near impossible to trace the exact origin. Unless you find the original collector and he remembers. You have the initials, right? You need a detective Paleo database, information and community Link to comment Share on other sites More sharing options...
Wrangellian Posted October 22, 2014 Share Posted October 22, 2014 Yes, Scott has sent me the paper for Gerastos ID but I am struggling with it (could take me hours - if I ever settle on a confident ID - which I'm not sure is worth it for this one measly specimen, never mind the detective!....) At least if I can narrow down the ID and location it will be an improvement on "Devonian, Morocco". Maybe I need to consider the lithology too, that table from the paper gives some description.. it is in grey limestone, with a black trilo. BTW I didn't mean to sidetrack Dave's topic, sorry Dave! Link to comment Share on other sites More sharing options...
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