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!

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