Wednesday, January 19, 2011

Geology on 35mm film #2 - Soft sediment deformation

Soft sediment deformation in the form of a small compressional fold, in the
Olanesti Formation (Eocene). Note the undeformed strata above and below
the fold.  The outcrop is located in a road cut, east of the Olt river.

Good examples of soft sediment deformation structures exist in the Eocene section of the Getic Basin in Romania.  The photographs give some examples of reverse faults and small compressional folds found in road-cut outcrops to the east of the Olt River.

These features most likely formed in a pro-delta environment, characterized by high sedimentation rates and relatively steep slopes.  Because of the high sedimentation rates, water did not expel easily from the recently deposited sediment.  This resulted in increased pore pressure immediately after deposition, which lead to displacement and movement of unconsolidated sediment.

Soft sediment deformation in the form of a small compressional fold.
The strata are Eocene in age and the outcrop is located east of the Olt river.
Soft sediment deformation in the Eocene strata, Getic Basin.
The section consists of silty mudstone with interbeds of sandstone.
The deformation is in the form of a reverse fault.

Sunday, January 9, 2011

Mud cracks revisited

In a previous post I showed a picture of the desiccation cracks that formed when a little pond on our Brenham property dried out this summer.  We visited three months later (yesterday), and found that the cracks in the mud weathered, and now look more like ant mounds.  The two pictures, side by side are shown below.
October 14, 2010                ©RomaniaRocks                          January 8, 2011
Three-month repeat photography of desiccation cracks, Brenham - Texas.
The picture to the left was taken immediately after the water in the pond evaporated; the mud on the bottom of the pond was exposed to the surface, it shrunk and cracked resulting in the polygonal shapes shown in the photo.  As the mud continued to dry during the three months of subaerial exposure, it lost its strength and started to crumble, taking the mounded form shown in the picture to the right.

Also very interesting is the fact that this polygonal pattern so characteristic to the desiccation cracks shows up in many places and at a variety of scales in nature, from beer foam, to the skin of a giraffe, to structures found at the nano-particle scales, to patterns found in the Universe.  The short video below  from University of Nottingham-Sixty Symbols describes very nicely the multi-scale occurrence of the polygonal pattern.

Saturday, January 1, 2011

The Danube, New Year, Vienna and Music

Odd combination one may say, but there is a common thread here.  On January 1st every year I watch the New Year's concert from Vienna; it is a family tradition, about which I blogged here one year ago.  The concert is centered around music from the Strauss family, and one of the most anticipated pieces every year is the Blue Danube waltz.  So there, you now see the connection.

The Danube River ends its "journey" in the Black Sea, where it forms the Danube Delta, which is one of my favorite places in Romania for many reasons: scenery, geology, landscape, people, the food, the culture, and the list could go on.

The Danube Delta (Romania and Ukraine). Image credit - Chelys, via Earth Snapshot.
The Danube Delta overlies two geologic provinces: the Scythian Platform and the Pre-Doborogea Depression.  The deltaic sedimentary complex is up to 400m thick and formed during Late Pleistocene - Holocene. The delta consists of three depositional systems: 1) a deltaic plain, which in the picture above is roughly the dark green area, from the first point of bifurcation of the Danube River (marked by the red circle in the photo above), to the shoreline; 2) the delta front parallels the coast and roughly coincides with the area where sediment plumes are visible in the water; and 3) the pro-delta, offshore of the delta-front, in water depths as deep as 50-60m.

In Vienna, on every January 1st, the Blue Danube waltz is the second of the three encore pieces played during the New Year's Concert.  The tradition is that the orchestra starts the music, and after the first few measures the audience interrupts with applause.  The conductor stops the music, turns towards the audience and wishes everyone a Happy New Year, after which the orchestra resumes the music.

I wish everyone a happy, healthy and prosperous 2011, and I am looking forward to some Champagne and waltz music tonight, including one of my favorites - the Blue Danube Waltz.

Happy New Year!

Wednesday, December 29, 2010

Romania viewed from above - Carpathians and the Black Sea

Envisat image showing the deep freeze that affected the southeastern Europe in January 2010.
Image source - European Space Agency

Weather in Europe has been very rough recently, so it looks like the year will end the same as it started: cold!  The picture above is from January 25, 2010 and it shows the deep freeze in SE Europe at the time.  The Carpathians are visible in the center left, the Danube Delta is seen in the center of the image, at the edge of the Black Sea.

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.

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.

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.
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.
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.
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 :)
Close-up view of the alluvial fan in Rocky Mountain Park, Colorado.

Friday, December 10, 2010

Earth as art #1

Photo credit - European Space Agency
Fascinating geomorphology in the Arctic tundra combined with modern technology (multitemporal Advanced Synthetic Aperture Radar), gives this amazing image that rivals the most creative human talent.
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Sunday, December 5, 2010

Rivers, geology and culture (#1) - Arges, Romania

A river represents the perfect fusion between geology and culture.  Rivers  are characterizesd, generally speaking, both by erosion and deposition; this is where the geology aspect comes from.  Think of the Grand Canyon and you can visualize the results of river erosion through time.  Take a canoe down or up a river, stop on the river bank for lunch and look around; the canoe trip and the lunch break will help you witness river processes, deposition and their resulting features.
Rivers are also amazing "cultural centers", in the sense that human settlements usually started along a river.  Any major city in Europe for example is  associated with a river: Paris-Seine, Vienna-Danube, Frankfurt-Main, Bucharest-Dambovita, Rome-Tiber, and the list could go on...  This is where the cultural aspect comes from.
With this post, I am starting a geological-cultural trip along a river, the Arges River in Romania, to be more precise; I imagine I am a rock particle (or a water molecule) originating from the Southern Carpathians and traveling along the Arges River all the way to the Danube.  The trip will witness some amazing history (geological and human), culture and landscapes.
The Arges River headwaters are located in the Southern Carpathians, between the two highest mountain peaks in Romania: Moldoveanu and Negoiu.
Google map showing the headwaters of the Arges River, located between Negoiu and Modoveanu, the highest mountain peaks in Romania.  Top of the map is towards South.
Geologic sketch of the area around
the Arges River (modified after  Mutihac, 1990). Note that only
the geology relevant to the Arges River is represented in color.
Cn2= Serbota crystalline series; Cn1=Fagaras crystalline series;
Pg=Paleogene; m=Miocene; N=Neogene
The Arges River has its headwaters in the metamorphic rocks of the Fagaras Mountains.  The views are breathtaking, the weather is harsh and as a result, the few motels and chalets that exist in the area function only during the summer.
The upstream part of the Arges River is probably most famous because it parallels the second highest paved road in Romania - the Transfagarasan. The road was built in early 1970's in response to the Soviet invasion of Czechoslovakia. Ceausescu, the Communist President of Romania at the time, wanted to have quick access across the mountains in case the Soviets attempted a similar move in Romania.  The road was built with heavy human (forty people lost their life) and financial sacrifice.
The next posts will take us to the Vidraru lake, then through the most upstream permanent settlements (villages) along the river; this will allow us to explore more geology and culture.
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