Stamberg-Member

Representation and status

Color CMYK

(0%,24%,62%,2%)

Color RGB

R: 250 G: 190 B: 95

Rank

lithostratigraphic Member (Subformation)

Validity

Unit is in Use

Status

valid formal name

Nomenclature

Deutsch

Stamberg-Member

Français

Membre du Stamberg

Italiano

Membro dello Stamberg

English

Stamberg Member

Origin of the Name

Stamberg (BL), südlich Liedertswil

Historical Variants

«Trigonodus-Dolomit» auct., Stamberg Member (Pietsch et al. 2016)

Description

Description

Hellbeiger, zuckerkörniger und poröser, schlechtgebankter Dolomit («Trigonodusdolomit») mit Oolithbänken und Lumachellenlagen im mittleren Teil, sowie zahlreiche Silexknollen im obersten Teil. Lokal reich an Bivalven und Gastropoden in den Dolomitbänken. Besonders die oberste Schichten, welche früher als Unterer Keuper definiert waren, sind reich an Makrofossilien. Lokal erscheint das Stamberg-Member sandig oder enthält Anhydrit.

Thickness

20 m (Fischer et al. 1971) ; 10 - 37 m (Müller et al. 1984) ; mittlere Mächtigkeit ca. 20 - 30 m, stark variierend wegen unterschiedlicher Dolmitisierung (Pietsch et al. 2016) ; bis 35 m bei Schinznach (Häring 1997) und 37 m in Benken (Nagra 2001).

Components

• gastropods
• bivalves

Hierarchy and sequence

Superordinate unit

• Schinznach-Formation

Subordinate units

• Kaisten-Bank
• Eptingen-Bank

Units at roof

• Asp-Member

Units at floor

• Liedertswil-Member

Upper boundary

Asp-Member

Lower boundary

Petrographische Grenze: Liesertswil-Member bzw. Kienberg-Member, falls die Dolomitisierung bis zum Trochitenkalk hinunter reicht.

Age

Age at top

• Early Ladinian

Age at base

• Early Ladinian

Geography

Geographical extent

Nordschweizer Jura.

Type area

Schuppenzone des frontalen Faltenjuras

Type locality

• Stamberg (BL), südlich Eptingen
  Site particularities
  • typische Fazies
  Coordinates
  • (2628625 / 1248025)
  Note
  • Merki 1961, Pietsch et al. 2016 Fig.12

Type profile

• Stamberg (BL), südlich Eptingen
  Site particularities
  • typische Fazies
  Coordinates
  • (2628625 / 1248025)
  Note
  • Merki 1961, Pietsch et al. 2016 Fig.12

Point of interest

• Tuttigraben (AG), Oberkaisten
  Site particularities
  • typische Fazies
  Site accessibility
  • Bachprofil
  Coordinates
  • (2646600 / 1265700)
  Note
  • Wildi 1983 S.42

Palaenography and tectonic

• Triassic of the Jura Mountains

Paleogeography

Northern Tethyan Carbonate Platform :
Plateforme de Bourgogne, ... = Northern Tethyan Carbonate Platform (NTCP)

Tectonic unit (resp. main category)

• Jura :
  Juragebirge

Kind of protolith

• sedimentary

Conditions of formation

Regressive sequence from marine (but later fully dolomitised) to coastal early diagenetic dolomite.

Metamorphism

non metamorphic

References

Definition

Pietsch Johannes S., Wetzel Andreas, Jordan Peter (2016) : A new lithostratigraphic scheme for the Schinznach Formation (upper part of the Muschelkalk Group of northern Switzerland). Swiss J. Geosc. 109/2, 285-307

The lower boundary is defined by the change from (dolomitic) limestone with single dolomitic strata to a laterally continuous and several m-thick pure dolomite. Single calcareous beds may occur within the Stamberg Member (compare mineralogic composition of borehole Weiach; Nagra (1989); Fig. 15) but the dolomite content has to exceed 90 percent. Macroscopically the dolomite varies considerably. Especially the upper part of the Stamberg Member typically shows a higher weatherability, which may arise from the texture prior to dolomitisation. The lower part often cannot be separated sharply from the underlying limestones of the Liedertswil Member visually. Matter et al. (1988b) recognise an offset of 1.75 m between a boundary set by macroscopic observation and a boundary set by the effective dolomite content. Because the lower, less erodible part of the Stamberg Member resembles the limestones of the Liedertswil Member, former investigators divided the dolomite in typical ‘‘Trigonodusdolomit’’ and dolomitic ‘‘Plattenkalk’’ (e.g. Merki 1961; Matter et al. 1988a). Due to the diagenetic nature of the lower boundary of the Stamberg Member, the level of the boundary varies within the Schinznach Formation. It is therefore possible that the Stamberg Member directly rests on the Kienberg Member, if dolomitisation reached down to the uppermost strata rich in crinoid detritus. The dolomites of the Stamberg Member nowadays have a mudstone appearance, but they mostly seem to have been mud- and wackestones prior to dolomitisation. Locally bivalve- and gastropod-rich strata occur within the dolomites (Herb 1957; Merki 1961). Especially the uppermost strata, which partly were defined to belong to the Lower Keuper formerly, are rich in macrofossils. Bonebeds occur in the upper part and contain, for example, fish and reptile teeth (Braun 1920). The Stamberg Member locally contains chert nodules. In Liedertswil (Fig. 11) they occur in stromatolitic dolomites, as also known from southwestern Germany, where stromatolitic dolomites are present in the upper part of the Rottweil Formation (Alesi 1984). Locally the Stamberg Member seems to be sandy (Disler 1914; Vonderschmitt 1942) or contains anhydrite (e.g. Vonderschmitt 1942; Matter et al. 1988a). The top of the Stamberg Member is defined by the first decimetre-thick mud or argillaceous marl layer of the Asp Member.

Important Publications

Pietsch Johannes S., Wetzel Andreas, Jordan Peter (2016) : A new lithostratigraphic scheme for the Schinznach Formation (upper part of the Muschelkalk Group of northern Switzerland). Swiss J. Geosc. 109/2, 285-307