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Author Topic: Tectites in Jamaica?  (Read 24670 times)

Offline susanshirleyjamaica

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Tectites in Jamaica?
« on: 07/09/2008 20:15:52 »
So sorry to submit this twice the easiest ones (chert and flint) The more I learn about those... the more I begin to learn about other beach stones.
However...  A couple of years ago, while looking in the field above the cliffs for black glass remnants of 18th century bottles... I came across what appeared to be an oddly shaped blob of black glass.  I figured it might some kind of primitive bottle stopper, but that didn't really make sense.  So I put it up figuring someday I might get a clue.
So just yesterday when I was searching thru my new rock books... I came across something I had never heard of before... a Tektite.
Jamaica doesn't seem to be the right location for these phenomena... but my sample meets the pictures and description so very exactly that I must wonder.  Can you give me any clues as to identifying this piece?

Much thanks for your kind help,


 

Offline Bass

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« Reply #1 on: 07/09/2008 21:53:46 »
Certainly resembles the few tektites I've seen- all of which were much smaller.

Were there any old mines, glassworks or smelters in the area where you found this?  What sort of other rocks were nearby?   
 

Offline susanshirleyjamaica

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« Reply #2 on: 07/09/2008 23:08:56 »
Hi Bass... This object was found in a bulldozed field which extends back from the cliff at which base I am finding all the wonderful rocks.  To my knowledge there were no glass works of any kind in this area.  Early settlers were Spanish and then English.  All bottles (and they sure left evidence of using ALOT of bottles) are European.  It was found near an area where a house once stood, perhaps in the late 1600's.  I'm going to see if I can add the other picture which I was having trouble with!
 

Offline susanshirleyjamaica

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« Reply #3 on: 07/09/2008 23:18:44 »
Sorry, you asked what other kinds of rocks are in the area... up on the flatlands it is just limestone and small river-stone type rocks.  I have never before in my life seen anything like this... until I saw it described in a book.  Do you suppose a settler could have brought it along from Europe as a good luck charm... or something like that?
I'd like to show you some of the amazing rocks I have found on the beach.  There are MANY breccias.  Your explanation of plates grinding together would seem to be the perfect explanation for these.  I am having trouble understanding the distinctions of chert, flint, smokey quartz and something that looks like quatz agate.

Thanks for your interest,
Susan
 

Offline Bass

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Tectites in Jamaica?
« Reply #4 on: 08/09/2008 04:57:04 »
Breccia!?

My favorite rocks.  What type of breccias?  Are they all the same?  Any pictures?

Will post some pictures of breccias on my project thread later this week.
 

Offline susanshirleyjamaica

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« Reply #5 on: 08/09/2008 14:44:47 »
I have found MANY breccias but I happened to have taken a picture of this one, my favourite, yesterday.  It is like a finely banded rock brocken up and cemented in a red matrix.  Has the look and feel of jasper.  I am showing it both dry and wet to try to show the colours.



 

Offline susanshirleyjamaica

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« Reply #6 on: 08/09/2008 15:34:19 »
Here is another breccia.  Could you tell me the correct pronunciation?  There are many more of different types... but I only just started collecting them.


 

Offline Bass

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« Reply #7 on: 09/09/2008 02:52:07 »
Nice ferruginous (iron oxide) breccia in top picture.  Appears to be mostly clast supported (supported by large fragments) with a mix of clasts in an iron rich matrix.  Definite rotation of the clasts- iron oxides are probably secondary (from weathering) since there is little alteration of the clasts.

Bottom picture- my guess would be karst collapse breccia.  Definitely clast suppported, and given Jamaica's karst topography, would not be out of line.  Does it bubble when you put acid on it (either the clasts or the matrix)? 

pronunciation: http://www.merriam-webster.com/dictionary/breccia
then press the pronunciation (audio) icon
 

Offline susanshirleyjamaica

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« Reply #8 on: 09/09/2008 18:39:50 »
The only think I have that resembles acid is vinegar... so I dunked the designated breccia in a bath of it, but very little fizzing.  Then I put another small breccia into the bath and it fizzed with gusto.



ok... I'm having trouble putting more than one picture on a post... so this is continued below.
« Last Edit: 09/09/2008 18:50:20 by susanshirleyjamaica »
 

Offline susanshirleyjamaica

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« Reply #9 on: 09/09/2008 18:52:26 »
Here's another pretty cool breccia... the matrix is quatz-like



continued below
 

Offline susanshirleyjamaica

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« Reply #10 on: 09/09/2008 18:55:59 »
ok... this is what I think is a jasper group.  The banded one looks very much like the clast material in one of the earlier pictures.



continued below
 

Offline susanshirleyjamaica

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« Reply #11 on: 09/09/2008 19:01:28 »
So... speaking of banded... can you tell me anything about this? Texture is chert/quartz-like.



continued below
« Last Edit: 09/09/2008 19:13:15 by susanshirleyjamaica »
 

Offline susanshirleyjamaica

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« Reply #12 on: 09/09/2008 19:11:00 »
ok... one more for this time.  Apologies, but I am going to keep picking your brain until you get sick of me!  (or until you decide to come to Jamaica and see for yourself!)   :-)

This is a group that seems to contain jasper and... copper?... blue stuff?? The one on the far left is way cool with diagonal band meeting horzontal band.



Maybe a stupid question... but how do I put more than one picture in a single post? 

Thanks a WHOLE lot for the help you have been giving me.  Every bit helps fill in the "big picture" for me.  I'm not done with rocks, but I have some neat fossils from the cliff face and beach. Would you like to see them?  I'll be very disappointed if you don't!  :-)
« Last Edit: 09/09/2008 19:16:43 by susanshirleyjamaica »
 

Offline JimBob

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« Reply #13 on: 10/09/2008 16:50:16 »
OK, first I am remiss in my promise, Susan, and I do apologize - I will eventually get the illustrations about the evolution of Jamaica up but see the subject for a temporary fix.

HUMM.... lets see, chert, green rocks, limestone and dolomite (the no phizz stuff) breccias, and possibly some of the green being originally a basalt-related rock, serpintine - sound suspiciously like the grand trinity of ophiolites. No, not ophiolitism but ophiolites.

the trinity - serpentine, pillow lava, and chert ("Steinmann's trinity") http://en.wikipedia.org/wiki/Ophiolite

I will venture a guess you live in eastern Jamaica. Why?, you may well ask.

An abstract of an article I am too cheap to purchase.

The ophiolitic Bath-Dunrobin Formation, Jamaica: significance for Cretaceous plate margin evolution in the north-western Caribbean

G. Wadge, T. A. Jackson, M. C. Isaacs and T. E. Smith

Two neighbouring areas of tholeiitic basalts, dolerites, isotropic gabbros and tonalites in eastern Jamaica are recognized as the upper section (~2.5 km thick) of an ophiolite. Limestones associated with this Bath-Dunrobin Formation contain a fauna of Upper Campanian and Lower Maestrichtian age. The basalts are overlain by a thick sequence of Maestrichtian volcaniclastic rocks and are faulted against a blueschist terrain. Since its emplacement the ophiolite has been subjected to uplift and major left-lateral strike-slip tectonism beginning in the Eocene. Recognition of this subduction zone complex and regional considerations of island arc polarity necessitates that ocean crust must have been consumed by a southward-dipping subduction zone. The overlying late Cretaceous/Palaeogene arc stretched from Guatemala through Jamaica to Oriente Province, Cuba. This arc separated the Yucatan Basin to the N, where active spreading accompanied subduction, from the Colombian Basin and the southern Nicaraguan Rise to the SE, where tholeiitic magmatism (B") penetrated older ocean crust. The Bath-Dunrobin Formation probably represents ocean crust from the Yucatan Basin obducted during the Maestrichtian. The major ophiolite terrains of Guatemala and Oriente, Cuba are by inference also derived from a proto-Yucatan Basin.


So now you know. If you do not live in Eastern Jamaica move there and don't make me look like a fool (again)!

Lastly, I doubt that it is a tektite BUT I am not sure.

Ok, I'll try to log on to PhotoBucket again to upload the fix for the other subject. 
 

Offline susanshirleyjamaica

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« Reply #14 on: 10/09/2008 17:09:06 »
Hi JimBob,

I still think it might very well be a tektite (I am so embarrassed to have spelled it incorrectly in my first post).  I did some research and found that a tektite field originating from Cuba includes Jamaica.  Also... this field seems to have heavier (larger?) tektites than others.  Could be?

I need to digest the info you just sent then will get back to you.  Yes, I live on the northeast coast of Jamaica.  There is a cliff face right below us which is providing fossils and though I don't know where they originated, the beach is littered with many different and beautiful rock types.

Can I ask you about fossils?  I have many whorls, both large and small... and I am trying to figure out what kind of shell they are from.

Thanks,
Susan
 

Offline RD

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« Reply #15 on: 10/09/2008 17:13:59 »
Jamaica is a stones throw tektites throw from Chicxulub
 

Offline susanshirleyjamaica

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« Reply #16 on: 10/09/2008 17:22:56 »
Oh!  Thank you for that link!  And JimBob... thanks for introducing me to the concept of the of ophiolite and the "trinity".  I am starting to "get it"!
 

Offline RD

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« Reply #17 on: 10/09/2008 18:21:47 »
Your "tektite" looks like the concretion in the green rectangle ...




http://web.utah.edu/unews/releases/04/jun/marsmarbles.html
« Last Edit: 10/09/2008 18:27:52 by RD »
 

Offline susanshirleyjamaica

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« Reply #18 on: 10/09/2008 22:18:10 »
Yes, that is it!  Thanks.  Now... is it unusual for such a band of ophialite to be exposed?  Am I especially blessed to have such a variety on one rock beach? 
So here are three more I picked up yesterday evening (my husband is beginning to think I am nuts!). The one on the left appears to have volcanic rock embedded in a sort of quartz.  Next is just another breccia in paradise.  On the right is an amazing rock with pink speckles and exposed quartz crystals.



So now I am going to bring out my fossils.  :-)
 

Offline susanshirleyjamaica

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« Reply #19 on: 10/09/2008 22:23:11 »
The urchin was found on the beach and the other two were dug (very carefully) out of newly exposed limestone cliff face.  Can you help me identify and date the two shells?  I know one is a scallop of some sort... and the other is some sort of huge snail ? or something?



and one more question below.
Thanks!
 

Offline susanshirleyjamaica

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« Reply #20 on: 10/09/2008 22:28:58 »
I am fascinated by the little curly things I have been collecting... I have tentatively identified them as whorls.  But could the big doughnut one be a whorl? or something else?  Many, MANY beach rocks have holes in them, like the one on far right... but don't seem to be whorls.  I'd really like to find out what animal these shell whorls might have come from... also, what could all the other holes be?



As usual... thanks so much for all the info...
 

Offline RD

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« Reply #21 on: 10/09/2008 23:17:24 »
This site may be able to ID your fossil shells ...

Quote
If you have a shell or a shell fossil at home and you just can't place an identification label to it, or is your snail doing something and you're not to sure just what, here's where you might get some help. I am but an amateur collector myself, but there are many good conchologists and malacologists that may be willing to help you.

Send your photos and collection data, if you have any, to me, Avril Bourquin . I will set up a file page for your shell or fossil shell then people can contact you personally in regards to their idea as to your shells proper identification. Please try to keep your jpg files small.

This kind of service is also available from some other GREAT shell collectors and dealers on their web sites. You may wish to seek out their assistance as well. Contact information forsome of these sites and people is located at the very bottom of this page.

Good luck in getting that definitive identification on your treasured shell or shell fossil.
http://www.manandmollusc.net/id_help.html

PS
     some of your holey finds look a bit like vertebrae, the holes being where the spinal cord passes.
« Last Edit: 10/09/2008 23:29:50 by RD »
 

Offline susanshirleyjamaica

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« Reply #22 on: 10/09/2008 23:36:08 »
Vertebrae?  Really?  That would be really neat... but I haven't found any other "body parts".
I will try that site, Thanks!
Susan
 

Offline RD

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« Reply #23 on: 11/09/2008 00:00:18 »
The rock on the left is a Septarian nodule


Your find on the right looks like it formed under similar conditions.
 

Offline susanshirleyjamaica

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Tectites in Jamaica?
« Reply #24 on: 11/09/2008 00:17:51 »
oh for a lapidary saw!  This is really the first rock that I've really wanted to look inside!
 

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Tectites in Jamaica?
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