Sunday, December 26, 2010

Geology on 35mm film - Conglomerates

I started going through my old 35mm slide collection representing geological field work from the pre-digital era.  Some of these places I will probably not visit again, at least not anytime soon, so I am bringing them to life with the help of a digital scanner.

The Paleocene rocks in the Southern Carpathians foredeep are represented by poorly sorted, massive, clast-supported conglomerates, which onlap  the crystalline basement.  They consist of angular fragments of schist up to 1m in diameter, as shown in the photo below.

©RomaniaRocks
Calimanesti Conglomerate on Topolog Valley, Southern Carpathians - Romania
The schist fragments are lithologically similar to metamorphic rocks in the Southern Carpathians.  The massive conglomerates grade upward into upward-fining cycles of conglomerate and sandstone, each cycle about 8m thick.



©RomaniaRocks
Upward-fining cycles of conglomerate and sandstone.
Calimanesti Conglomerate, Valsan Valley-Romania.
The upward-fining cycles have a clear erosional base, and the lithology of the clasts are more diverse, consisting not only of crystalline rocks, like lower in the section, but also of sandstone and limestone.
©RomaniaRocks
Calimanesti Conglomearte, Valsan Valley - Romania.
Note the erosional base and fining-upward character.
The sandstone at the upper part of each cycle is medium- to very coarse grained and massive, flat-beddd or cross-laminated.
©RomaniaRocks
Calimanesti Conglomerate, Valsan Valley-Romania. Note the erosional base,  
large fragments of crystalline rocks and the finning-upward character
The conglomerates described above were deposited by overlapping alluvial fans sourced by the Southern Carpathians.  The poorly sorted, angular, coarse textured deposits, with fragments up to one meter in diameter are indicative of debris flow deposits, a common occurrence in alluvial fans.  The Paleocene landscape of Romania was probably not too different than the landscape in the photo below, from the Rocky Mountain National Park in Colorado.
©RomaniaRocks
Alluvial fan at the mouth of a canyon in Rocky Mountain National Park, Colorado.
A hike on top of the fan in the Rockies reveals the size and complexity of the fan.  I bet a hike in the Paleocene in Romania, on top of the Calimanesti Conglomerate would have been somewhat similar, less the ability to use the humans for scale :)
©RomaniaRocks
Close-up view of the alluvial fan in Rocky Mountain Park, Colorado.

7 comments:

  1. good photos.. very similar to the Miocene-Pleistocene conglomerate sandstones packages deposited in the Himalayan foredeep.. those too are alluvial fans deformed today to form the Siwalik ranges

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  2. How did you digitize your slides?

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  3. Suvrat, thanks for the comments, I wish one day I will be able to see the conglomerates in the Siwalik ranges.
    Slver Fox, I recently purchased a slide/film scanner (Wolverine). It is OK but not great, but better than the one I had before. I wish, thought, I can find something better; one that would give me more ability to "play" with the image and modify after scanning and before saving.

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  4. The best scanners, like the ones here, are fairly expensive. I'm trying to decide if I'd get more done if I buy one, or if I should just buckle down and send some out. This place uses the Nikon 9000 scanner, the best.

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  5. Thanks, Silver Fox, good advice. I may try to send some slides out just to check out the process. My only fear: what if my slides will get lost?

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  6. Actually thanks for posting something useful..

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