«Murchisoni-Kalk»
Back to Lower HelveticRepresentation and status
- Color CMYK
- N/A
- Color RGB
- R: 120 G: 120 B: 120
- Rank
- lithostratigraphic unit
- Validity
- Unit is not in Use
- Status
- incorrect name (though informally used)
Nomenclature
- Deutsch
- «Murchisoni-Kalk»
- Français
- «Calcaire à Nummulites murchisoni»
- Italiano
- «Calcare a Nummulites murchisoni»
- English
- «Murchisoni Limestone»
- Origin of the Name
-
Namengebendes Fossil: Foraminiferenart Nummulites murchisoni. Diese Art ist jedoch bis im unteren Teil des «Grauen Nummulitenkalks» vorhanden.
- Historical Variants
-
Murchisonikalk = Murchisonkalk [sic] (Jeannet et al. 1935), Granulosa-Murchisonikalk (Ochsner 1975), Murchisoni horizon (Lihou 1995), Nummulitenkalk
Description
- Thickness
- 1,1 - 2 m ; 1,6m am Sihlsee (Jeannet et al. 1935)
Components
- glauconite
- nummulites
Nummulites "Murchisoni"
Hierarchy and sequence
- Units at roof
Age
- Age at top
-
- late Ypresian
- Age at base
-
- middle Ypresian
Palaenography and tectonic
-
- Tertiary
- Paleogeography
-
North Tethyan Shelf
:
marge continentale européenne - Tectonic unit (resp. main category)
-
-
Östliches Helvetikum
:
u.a. Glarner Alpen
-
Östliches Helvetikum
:
- Kind of protolith
-
- sedimentary
- Conditions of formation
-
neritisch
- Metamorphism
- non metamorphic
References
- Definition
-
1995) :
A new look at the Blattengrat unit of eastern Switzerland: Early Tertiary foreland basin sediments from the south Helvetic realm Eclogae geol. Helv. 88/1, 91-114
(
p.104: The first hardground in the Nummulitic Limestone marks the base of the Murchisoni horizon, named after the common occurrence of Nummulites murchisoni, a lower to middle Cuisian nummulite (Schaub 1981). In Weisstannental, the Murchisoni horizon is represented by a calcareous greensand with echinoderm debris, that passes southeastwards into a sandy limestone at Gula-Schwamm (Fig. 5). East of Elm, the same stratigraphic horizon thickens to the south and passes into a limestone-rich facies in the Fanenstock profile (Fig. 4). There, the hardground is overlain by a limestone breccia containing Operculina sp. and Globigerina sp.; whilst Operculina sp. inhabits a range of water depths (0-130 m) (Murray 1991), globigerinids are rare at depths of less than 40 m, and only abundant above 80-100 m (Brasier 1980). The limestone breccia passes upwards into a glauconitic foraminiferal limestone with very big nummulitids and discocyclinids; the bias towards large B-form nummulitids either arose by winnowing out of smaller A-forms by bottom currents, or selective transport of larger forms during high energy storm events (Crampton 1992). In situ faunas are dominated by A-forms in an A:B ratio of 10:1 (Blondeau 1972).