(FM) Flysch Stratigraphic Suite -- Molasse Basin, Switzerland

Title

(FM) Flysch Stratigraphic Suite -- Molasse Basin, Switzerland

Alternative Title

Typical turbidite sequence rocks (predominantly clastics with some evidence of carbonate input)

Identifier

FM 1-11

Description

Flysch is dominantly a turbidite succession, alternating sandstone and shale 100mm to rarely 100m in syntectonic accumulations. With a rising landmass shedding clastic debris into "deep" troughs, oversteepening of sediments along the shelf or actual tilting of the shell initiated turbidity currents flows deeper into the marine basin. There may be hundreds of these units in a given section. Nappes then over rode the soft sediments, locally producing strong deformational structures in the flysch sediments. 

The nappes shed their debris into fresh marine environments in great fans with large accumulations of coarse conglomerates. A molasse section may be a thousand meters thick. Molasse comprises a clastic sedimentary succession in a post-tectonic environment.

Flysch and molasse both have sedimentatlogical as well as tectonic implications associated with their appearance in an outcrop.  

Dr. Trumpy at the Geological Institute in Zurich suggested specific localities for collecting and arranged for Dr. Hanspeter and Mr. Freeman to take me into the field on successive days. Later, Mr. Freeman spent several days in order to procure this suite.

A set of kodachrome slides is available and should be used with the specimens to put the rocks into relationships seen in the field. There are 11 slide specimens. All slide specimens were photographed in PPL and XPL.

Date

Oct. 10, 2013

Contributor

Western Minerals, inc.

Spatial Coverage

Molasse Basin, Sternenberg, Germany

Temporal Coverage

In the Late Eocene, the area subsided again and developed into the Molasse Basin.

Accrual Method

Purchased by Western Minerals Inc.

References

Start Here:
Eynatten, H.V., 2003, Petrology and chemistry of sandstones from the Swiss Molasse Basin: an archive of the Oligocene to Miocene of the Central Alps: Sedimentology, v.50, p.703-724. http://dx.doi.org/10.1046/j.1365-1309.2003.00571.x

  • Fluvial sandstones from the Swiss Molasse Basin were analyzed for sandstone framework composition, heavy minerals, whole-rock geochemistry and detrital chrome spinel chemistry to understand its provenance.

Additional resources:
Schlunegger, F., Matter, A., Burbank, D.W., and  Klaper, E.M., 1997, Magnetostratigraphic constraints on relationships between evolution of the central Swiss Molasse Basin and Alpine orogenic events: Geological Society of America Bulletin, v.109, p.225-241. http://dx.doi.org/10.1130/0016-7606(1997)1092.3.CO;2

  • Magnetostratigraphic chronologies, together with lithostratigraphic, sedimentological, and petrological data enable detailed reconstruction of the Oligocene to Miocene history of the North Alpine foreland basin in relation to specific orogenic events and exhumation of the Alps. 

Sinclair, H.D., 1997, Flysch to molasses transition in peripheral foreland basins; the role of the passive margin versus slab breakoff: Geology, v.25, p.1123-1126. http://dx.doi.org/10.1130/0091-7613(1997)0252.3.CO;2

  • It is proposed that slab breakoff may have been responsible for the increased sediment supply that resulted in the flysch to molasse transition in the North Alpine foreland basin, and that this provides an alternative to the passive margin model. 

Spiegel, C., Siebel, W., Frisch, W., and Berner, Z., 2002, Nd and Sr isotopic ratios and trace element geochemistry of epidote from the Swiss Molasse Basin as provenance indicators; implications for the reconstruction of the echumation history of the Central Alps: Chemical Geology, v.189, p.231-250.

  • Uses a combination of events to explain the geodynamic scenario of large-scale lateral extension processes affecting the Central Alps in post-collisional times. 

Willet, S.D. and Schlunegger, F., 2010, The last phase of deposition in the Swiss Molasse Basin; from foredeep to negative-alpha basin: Basin Research, v.22, p.623-639. http://dx.doi.org/10.1111/j.1365-2117.2009.00435.x

  • Simple analytical theory for the necessary conditions for such a negative-alpha basin to develop and be maintained.

Subject

Turbidite sequences and carbonate pulses of deposition in a basin.

Abstract

The collection consists of a variety of shale, sandstones and conglomerates that illustrate sediment trapped in a molasse basin.

Collection Items

OCR PDF Supplementary information for the Flysh Molasse suite.

Fossiliferous Biofloatstone in a mud matrix
Fresh water marl with plant remains. Specimens selected to include leaf and or stem remains. Hand sample specimen is small and crumbly. Fossil bearing biofloatstone composed of soft silt, mud and limestone matrix, with carbon imprint and original…

Conglomerate
Conglomerate, dominated by carbonate pebbles). Only a medium grained (1-10cm) facies collection of out of what was perhaps a 50ft exposure of coarse conglomerates. Light pink quartzite pebbles are interpreted to have been deposited during the…

Calcareous Sandstone
Fine grained relatively soft calcareous sandstone. Thin Section Fine angular grains with fairly close packing characterize this thin section, with unusually sharp angles. Sample is still clay dominated.

Shale
Organic rich to moderate black to light grey shale. Some parts of FM-4 are silty shale. Minor rust stains are present on lighter samples. Representative of upper portion of a turbidite sequence.

Thin Section
Very fine (

Sandstone
Gray, medium to coarse grained quartz-rich lithic sandstone with rip up clasts and mud rich areas present. Thin Section Fine, (.7-.1 mm) sub angular crystal fragments floating in mud matrix, with feldspar, quartz, and pyroxene present.

Light Sandstone
Coarse grained mainly quartz sandstone with minor lithic and mud incorporated. Cross bedding present. Note the larger grain size of the sample, as well as the grains composed of conglomerate material indicating reworking of older sediments. Present…

Conglomerate
Poorly sorted, coarse grained conglomerate; bearing chert, quartzite and granitoid fragments in calcite cement, with an odd mica flake indicating very short transport. The facies that this rock is representative of is uncommon. Conglomerate beds at…

Fine Banded Sandstone
Very fine grained sandstone and silty shale noted between shale and dark, fine grained sandstone (sample 4 &5).

Thin Section:
Very fine sized sub rounded grains of pyroxene, quartz, and feldspar in a calcic matrix.


Shale
Shale, foliated, and bearing organic matter, from the interbeds between sandstone layers. Fine grained laminated sands between shales were uncollectible, but present. Friable and fragile.

Thin Section:
Very fine to fine grain, poorly sorted…

Sandstone
Sandstone with ripple marks and cross bedding and strong flute casts along surface indicating mid-high energy. Poorly sorted coarse sandstone with ripple marks, cross bedding and strong flute casts, as well as small pebbles that vary from angular to…

Conglomerate
Collected from blocks moved during road construction. Have been moved perhaps 200 yards. More quartzite and igneous and crystaline metamorphic rocks than at Sternenberg sampling site. Thin Section Coarse to fine (7-.1 mm) poorly sorted grains of…
View all 12 items