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Author Topic: What is the geological origin of Jamaica?  (Read 24407 times)

susanshirleyjamaica

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What is the geological origin of Jamaica?
« on: 31/07/2008 13:27:19 »
Hi...     
I live in Jamaica and have recently become fascinated with the great variety of fossils,rocks and geological formations found here. I grew up in Michigan and as a child spent many happy hours scouring the glacial "gravel pits" for fossils, and of course found many. The "rock-hound" in me has been re-awakened but the geology here is mind boggling compared to the glacial landscape of Michigan. Can you help me find information on exactly how Jamaica's geology evolved?  I have read that both volcanic and tectonic activity were invoved and that the island was submerged and raised several times. From doing a little googling on plate tectonics, I have also learned that Jamaica originated far west of where it is now, relative to Cuba.  But I need to know much more!  PS. I originally posted this question in the wrong forum (not called a newbie for nothing!) and was referred here.  I hope I've got it right this time!
Thanks,
Susan
Susanshirleyjamaica


[Mod edit - subject re-formatted as a question. Please try to do this where possible as it makes it easier for people to find your post and reply]
« Last Edit: 04/08/2008 16:41:24 by chris »

Evie

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What is the geological origin of Jamaica?
« Reply #1 on: 07/08/2008 19:31:09 »
I think you may have answered your own question! Yes, Jamaica was originally formed through volcanism (80-100 mya), rose above sea level, then began to subside (during which limestone and shale were deposited, where you probably find your fossils), and then rose above sea level again through tectonic uplift. If you are looking for in-depth scientific research, a local library is your best destination. You can find scientific geology papers online, but usually have to subscribe in order to read the paper in its entirety. Here's a few websites I came across while fact-checking:

http://en.wikipedia.org/wiki/Geography_of_Jamaica/
http://www.cockpitcountry.com/formjamaica.html/
http://users.skynet.be/sky33676/karst.html/
http://energy.ihs.com/Resource-Center/Lease-Rounds/jamaica/geological.htm/

susanshirleyjamaica

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What is the geological origin of Jamaica?
« Reply #2 on: 11/08/2008 14:16:57 »
Thanks! I like your simple basic explanation... it helps put other things I have learned into perspective.
While waiting for answers... I did quite a bit of on-line research and ordered several books... most interesting might be "Caribbean Geology into the Third Millennium: Transactions of the Fifteenth Caribbean Geological Conference" though it may be academically way over my head!
I will now check out the links you gave me.

I live on the north coast of Jamaica where the Rio Nuevo enters the sea.  It is a "rock beach" and has an unbelievable variety of rock types.

Bass

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What is the geological origin of Jamaica?
« Reply #3 on: 16/08/2008 05:42:24 »
Having never visited Jamaica (but would love to come visit-hint,hint), this is from general Caribbean geology and literature review.
Jamaica is located on the northern edge of the Caribbean plate, not far from the plate boundary with the North American plate.  The plate boundary is the Cayman Trench, a large left-lateral fault (similar to the San Andreas Fault).
The oldest rocks are Cretaceous (>65 million years old), and are a mish-mash of metamorphic, sedimentary and igneous rocks- which is why you find so many interesting varieties of rocks on the beach. At the beginning of the Tertiary (<65 million years ago), Jamaica underwent a period of extension, or pulling apart, resulting in NW trending fault blocks and subsidence below sea level.  As the land continued to subsided, reefs in the shallow ocean formed the massive limestone beds that cover most of the island and allow for the characteristic "karst" (cave) landforms over the majority of the island.  Rainwater dissolves the CaCO3 in the limestone, creating caves, sinkholes and buried rivers.

Jamaica re-emerged during the Eocene (40 to 60 m.y. ago) as volcanoes once again erupted on the island.  With the more recent development of the Cayman Trench, Jamaica has been uplifted, squeezed and ripped by E-W trending faults.  Below is a general geologic map of Jamaica (from about.com)



As you can see, most of the island is covered in Limestone (yellow), but the really interesting rocks are on the eastern half of the island.

Hope that helps.
« Last Edit: 16/08/2008 05:45:12 by Bass »

susanshirleyjamaica

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What is the geological origin of Jamaica?
« Reply #4 on: 16/08/2008 13:24:25 »
Hey, thanks allot!  Your explanation helps to put some of the "bits and pieces" together for me.  As a matter of fact, I live on the Northeast coast and according to your map, we drive right through the most geologically varied areas everytime we go back and forth to Kingston, on the south of the island.  I have lots more questions like why do so many of the fossil rocks (rounded by either sea or river) have clean holes right through them, and why is the chert coated with thick layer of white limestone and worn into smooth balls and egg shapes. But at least I feel like I am pointed in the right direction and am no longer completely mystified by Jamaica's amazing geology.  I have already gotten a geologists pick (pic?) and cold chisel and plan to take some samples and pictures while my son visits next month.
Thanks again!
Susan

JimBob

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What is the geological origin of Jamaica?
« Reply #5 on: 10/09/2008 16:13:29 »
This is the start of the process - the rest is going to be up one of these days.

This is about 70 million years ago - but DO NOT quote me on the age. I have not gone back to the source of these drawings I annotated to make sure.

« Last Edit: 10/09/2008 16:16:47 by JimBob »

susanshirleyjamaica

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What is the geological origin of Jamaica?
« Reply #6 on: 10/09/2008 22:26:52 »
Thanks...  I had come to understand that Jamaica sort of broke off the Yucatan area... but it is really strange, while at the same time really cool, to realise that Jamaica started out so very far west!  At what geological point did it submerge... and about when did it push back up?  Was it mostly volcanic island building or tectonic "mountain building" that lifted it up.  I picked up that term on a BBC documentary.  :-)

Klondyk

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What is the geological origin of Jamaica?
« Reply #7 on: 15/10/2008 16:09:55 »
Hey JimBob!

I'm currently writing my exam at the University of Hamburg. The topic is a "Geosystemanalyse of Jamaica" and I would like to ad the map you posted to my writings. All I need to know is the exact origin/source of the map! It's all about the scientific rules, you know ;) Originator, Title, Page etc.... Maybe you would be so kind and send me an answer! Thanks in forward!


JimBob

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What is the geological origin of Jamaica?
« Reply #8 on: 15/10/2008 22:35:27 »
Klondyk: the maps are from this link.

http://www.dinodata.org//Golonka/Golonka.htm

There is a whole series from before this to the present at this site - with discussion.

-------------------

Thanks...  I had come to understand that Jamaica sort of broke off the Yucatan area... but it is really strange, while at the same time really cool, to realise that Jamaica started out so very far west!  At what geological point did it submerge... and about when did it push back up?  Was it mostly volcanic island building or tectonic "mountain building" that lifted it up.  I picked up that term on a BBC documentary.  :-)

Jamaica started out as a volcanic platform, similar to Japans islands, and through accretion (coral reefs, etc.) and erosion (the breccias you have posted) was at times above and below sea level that ended up with the island at present (what? Did you think it was Fairyland?) The serpentines you posted are the remnant of the oldest part of the island.


Klondyk

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What is the geological origin of Jamaica?
« Reply #9 on: 18/10/2008 21:19:45 »
Thanks, JimBob! That'll do...!

There's another thing that bothers me: I cant't find a map showing a cross-section of the Jamaican underground! All I have is a 'Sequence of Geological Formations' from Rober T. Hills book "Geology and physical Geography of Jamaica". The book's out of 1899(!!), yet it's still a fantastic work regarded from a modern point of view!

Maybe somebody can help me with a proper map of the underworld!

Klondyk

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What is the geological origin of Jamaica?
« Reply #10 on: 21/10/2008 17:33:37 »
Here's another Link to the topics scientific debate. It's a pretty new paper out of Current Science.

Rao, T. Ramamohana: „Geological Evolution of the Carribean Plate: Some critical aspects in the two divergent models”, Current Science, Vol. 95, No.6, 25.9.2008

http://www.ias.ac.in/currsci/sep252008/736.pdf


Barrettia

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What is the geological origin of Jamaica?
« Reply #11 on: 23/10/2008 17:17:39 »
I am a Professor at UWI in Kingston and can point you in some directions.

A four phase model for the evolution of Jamaica works - this was originally suggested by Gren Draper, and has been a little modified by me.

1. Island Arc phase (Cretaceous to Paleocene or 140 to 60 million years ago). Jamaica was part of a volcanic island chain, much like the Lesser Antilles today. The rocks include lavas and sediments derived from the volcanoes. These sediments range from conglomerates to sandstones to shales, and depending on how close you are to the volcano, the amount of lava decreases or increases. So in eastern Jamaica, volcanic rocks predominate, whereas in western Jamaica sedimentary rocks predominate. Limestones are also present and the most characteristic fossils are rudists (aberrant extinct clams) that grew up to 200 cm in size or more. Jamaica has some 120 species of rudist.

2. The extension phase (Late Cretaceous to Early Eocene 70 to 50 million years age). This includes extension with the formation of basins - the best known is the Watwager Trough. This has some 9 km thickness of sandstones and conglomerates with minor lavas.

3. The quiescence phase (Eocene to middle Miocene, 50 to 13 million years ago). Jamaica gradually subsided and eventually all was bathed by shallow waters. The rocks change from impure carbonates and conglomerates, sands and shales, to pure limestones of the White Limestone.

4. Uplift and deformation (13 million years to present). Interactions between the Caribbean Plate and North American Plate led do deformation shortening and uplift (also in Hispaniola). The mountains and plateaus rose, were eroded and the older rocks exposed. The Coastal Group was deposited around the fringe of the island and is represented by coral reef deposits. The White Limestone karstified to form the cockpits and cave systems so characteristic of Jamaica's topography.

Sadly, there is no real book for the interested amateur. I may write one one day. There are some good resources though.

The Geological Museum at UWI (Geography and Geology Department) has displays of rocks and fossils from Jamaica and is free. It is open on week days.

The Geological Society of Jamaica organises fieldtrips for both Professionals and Amateurs. Their web page is http://gsj.monainformatixltd.com/

The University has some stuff (my page has some papers on Jamaica as pdfs - some links may not work. I just looked and the page is down at moment but should be back up soon)

http://www.mona.uwi.edu/geoggeol/Staff/Mitchell/sfmitchell.htm

Hope this is useful,

Simon


Bass

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What is the geological origin of Jamaica?
« Reply #12 on: 23/10/2008 18:52:23 »
Informative post Simon!  Welcome to the forum.

JimBob

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What is the geological origin of Jamaica?
« Reply #13 on: 24/10/2008 22:21:50 »
Informative post Simon!  Welcome to the forum.

I would like to echo the welcome - but I also must let you know you have crushed one of the beliefs I have had since college. There is a black Mississippian Limestone near where I went to school that is full of rudists. The proper thinking of the time was that they were an aberrant form of coral. OH, LOrd How long will I live with outdated knowledge of paleo?

If I may ask, Simon, when were they reclassified to Mollusca? How long have I been out of date?????????

Please don't tell me 40 years - please!
 

Barrettia

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What is the geological origin of Jamaica?
« Reply #14 on: 25/10/2008 01:07:13 »
Hi Jimbob,

Not wanting to crush anything - but more than 100 years ago!

I tell you what. I will post a few pictures of some rudists from Jamaica for everyone to see - AND say what they mean.

Tomorrow,

Simon

JimBob

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What is the geological origin of Jamaica?
« Reply #15 on: 26/10/2008 00:45:38 »
Hi Jimbob,

Not wanting to crush anything - but more than 100 years ago!

I tell you what. I will post a few pictures of some rudists from Jamaica for everyone to see - AND say what they mean.

Tomorrow,

Simon

GAD! I have been duped! The professor who led the field trip was a prominent Cretaceous stratigrapher. If it wasn't an ammonite, it didn't count as a fossil to him. That is probably why he fobbed it off as a coral.

susanshirleyjamaica

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What is the geological origin of Jamaica?
« Reply #16 on: 20/11/2008 21:50:04 »
I've been away and haven't checked the site recently.  I was surprised to see the conversation continued after I last saw it.

Thanks all... especially Simon at UWI

Susan

 

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