Transcript The Harz Mountains…..

Harz Excursion – March 2006
(or…. where are these crazy geologists taking us??!!!)
The Harz Mountains…..
- Mittelgebirge – “low mountain range”
- 180km long x 30km wide
- 400 – 1100m elevation
Geology of the Harz
- formed by tectonic uplift 140Ma – 70Ma
- consists of rather old rocks surrounded by younger rocks
- all major rock types present (igneous, sed., and meta.)
- “klassische oder goldene Quadratmeile der Geologie" Goethe, 1784
Mining in the Harz
• sulfidic lead (Pb) and zinc (Zn) ores
• gold and silver coined in Goslar
Geologic
Time Scale
408 – 360 Ma – Devonian Period
- sharks, bony fishes appeared
- oceans dominated by reef builders
- first amphibians
- first seed plants (earliest trees)
- late Devonian extinction had little effect on land
- 22% marine families, 57% marine genera
408 – 360 Ma – Devonian Period
350 - 285 Ma – Carboniferous Period
- early climate is warm, lush plant growth
- hydrocarbons
- O2 levels highest in history of earth (35%?)
- amphibians colonize land, dominate
- amniote egg allows certain tetrapod amphibians to
give rise to synapsids and reptiles
- Gondwana moves south and climate cools
350 - 285 Ma – Carboniferous Period…continued
350 - 285 Ma – Carboniferous Period…continued
285 – 245 Ma – Permian Period
- Formation of supercontinent Pangea
- first time continental area > oceanic area
- therapsids and gymnosperms dominate land, drier
- largest extinction with two pulses
- 1st coincides with glacial pulse
- 2nd larger, fast, >80% species die
- causes – flood basalts, anoxic pulse, impact?
285 – 245 Ma – Permian Period…continued
Middle Devonian, 385 Ma b.p.
clastic sediments in basin
mafic extrusives at rifts
carbonate reefs on highs
Upper Carboniferous, 305 Ma b.p.
Intense deformation (folding)
during Variscan Orogeny
End of Upper Carboniferous, 300 Ma b.p.
Intrusion of felsic magmas of
Brocken and Ramberg plutons,
contact metamorphism
turns sedimentary country
rocks into hornfels,
first vein mineralization
Permian (Rotliegendes), 280 Ma b.p.
weathering and erosion,
deposition of sediment in
intramountaneous basins
and in the foreland
Upper Permian / Triassic, 250 Ma b.y.
erosion to peneplain
below sea-level,
formation of evaporites
(carbonates and salts)
under arid climate
Upper Cretaceous, 80 Ma b.p.
renewed uplift!
younger sequences
surrounding the Hars Mts.
are folded, tilted and
dragged upwards,
contineous erosion removes
post-Carboniferous rocks and
exposes granite plutons
Re-newed uplift in the Upper Cretaceous
exposes pre-Permian rocks of the Hars Mts.
and drags post-Carboniferous rocks upwards