reconstruction of palaeoclimate - sedimentology
Reconstruction of Palaeoclimate - Examples of Data Sources
 qualitative data for climate analysis in decades to million-year range, e.g. distribution of marine and non-marine climate sensitive fauna and flora climate sensitive marine and non-marine sediments synthesis of biotic and abiotic climate indicators
 sedimentological examples laminated sediments varvites
 Examples for environment and climate reconstruction newsbusters.org

reconstruction of palaeoclimate - sedimentology
Varvites as archive for environmental processes rhythmite: laminated sediment with periodic repetition varves: rhythmic sediments with annual character, formed in lacustrine and marine environments.
type (De Geer 1912, Sweden ) consists of a silty, graded summer -layer and a winter -layer of clay and refers to laminated deposits in glacial lakes. extended definition
Varves form in a variety of marine and lacustrine depositional environments from seasonal variation in clastic, biological, and chemical sedimentary processes.
http://en.gtk.fi/export/sites/default/Research/images/varves2.jpg

reconstruction of palaeoclimate - sedimentology
Clastic Varves
Variation in clastic sedimentation from seasonal/annual runoff
- in subarctic or boreal environments runoff associated with winter/summer seasons
- in subtropical and tropical environments runoff seasonality mainly controlled by Monsoonal circulation or other factors controlling the rainy season
Caution: In arid environments clastic layers might represent non-seasonal flood events rather than annual sedimentation.
Biogenic Varves
Seasonal variation in bio-production
- caused by seasonal changing insolation, life cycles of (planctic) organisms and stratification of the water column
- often linked with seasonal clastic sedimentation
Evaporitic Varves
Formed in saline lakes of semi-arid and arid regions when seasonal/rythmical evapotranspiration exceeds precipitation.
- evaporite minerals that may precipitate are carbonates, gypsum and halite,etc.
- depending on solubility of evaporit minerals, characteristic sequences could be formed
Those types occur in non-marine and marine environments as well; could be combined in different manner.

Varves form in a variety of marine and lacustrine depositional environments from seasonal variation in clastic, biological, and chemical sedimentary processes.
dual lamination triplet lamination quadrouplet lamination
Interpretation:
number of laminae depents on climate types
 intensity of seasons and linked abiotic/biotic processes climate with two seasons climate with four seasons

bedding types of fluivial and lacustrine deposits
New Zealand, Mt. Cook subaquatic, shallow lacustrine - Litoral lacustrine-pelagial  Varves fluvial subaquatic, transition fluvial-lacustrine

Clastic varves - classical glacial varves examples for proximal and distal types
 in subarctic or boreal environments runoff associated with winter/summer seasons proximal glacial varve - couplet of two layers between 0.5 and 50 cm distal
“winter” layers (dark), usually >90% clay, often gradational with the top of the preceding summer layer below, sharply truncated at the base of the following summer layer
“summer” or melting season layers multiple micro-graded beds or laminations, showing often a general fining upward and may grade into the “winter” layer above. distinct graded bed of sand and silt mark the beginning of the melting season layer – sharp base
„Bänderschluff“ typical banded silt/clay; light layers – coarser summer deposits, dark layers - clay-rich winter deposits
Macherslust near Eberswalde, Brandenburg de.academic.ru/pictures/dewiki/66/Baendertone.JPG
Typical distal varved clay, lake deposits;
Passumpsic Valley, East Barnet, Vermont, USA http://geology.tufts.edu/varves/Geology/varves.asp

Non-glacial clastic varves
Variation in clastic sedimentation from seasonal/annual runoff
 in subtropical and tropical environments runoff seasonality mainly controlled by
Monsoonal circulation or other factors controlling the rainy season
(In arid environments clastic layers might represent non-seasonal flood events rather than annual sedimentation.)
Clastic lamination depents on
• sediment supply
• lake size, morphometry, stratification
• preservation potential – no bioturbation !
Investigation techniques:
- digital image analysis of sections or cores
- digital grain size analysis or color density analysis
 calibration to a climatic variable, e.g. sunspot cycle, El Niño-Southern
Ossicillation http://en.gtk.fi/export/sites/default/Research/images/varves2.jpg

Marine combined clastic-biogenic varves – modern example marine varves
monsoonal climate
Pakistan coast
Formed by
seasonal variation in upwelling which cause algal blooms  a
seasonal variation in clastic sediment supply from aeolian input, river discharge and wind driven coastal sediment transport along the shore  b
Schulz et al. 1996

Marine combined clastic-biogenic varves – modern example marine three-component varves
warm-humide climate
Gulf of California
Formed by
seasonal variation in insolation rate cause different algal blooms
seasonal variation in clastic sediment supply from aeolian input and river discharge

Biogenic Lamination / Varves
Seasonal variation in bio-production are caused by
- seasonal changing insolation, life cycles of (planctic) organisms and stratification of the water column
- often linked with seasonal clastic sedimentation
- mainly expressed in more or less regular alternation of organic and clastic laminae
Biogenic lamination depends on:
• seasonal changing bio-productivity in the aquatic environment – e.g. plankton/algal blooms
• seasonal growth of microbial mats – stromatolithes, oolithes
• seasonal entry of terrestrial organic material – pollen, plant leaves etc.
• seasonal biogenic and/or abiogenic induced precipitation of minerals e.g. calcite, vivianite (iron(II)-phosphat)
• seasonal sediment supply
Seasonal stratification and circulation of lake water masses example: dimictic lake thermocline caused by density anomaly
 maximum density for freshwater is 4 °C stratification  water masses with different properties
salinity (halocline), oxygenation (chemocline), density (pycnocline), temperature (thermocline)  form layers that act as barriers to water mixing
- dimictic lake undergoes stratification in the summer and winter and complete overturn in the autumn and spring,
during winter, surface ice prevents mixing by the wind,
with cooler water (0° C) staying near the surface, warmer, more dense water (4° C) extending to the bottom.

Biogenic lamination – postglacial lake Holzmaar example autum summer lake Holzmaar , Eifel spring biogenic varves
Holzmaar, scale bar 0,2 mm winter typical 1-year-varve
Annually laminated, non-glacial lake sediments from Lake Holzmaar (Eifel, western Germany)
absolute age of varve intervals with variations in thickness and composition correlated to climatic changes recorded by glacier fluctuations in the Alps.
Back to 8800 years VT (varve time = varve years before 1950) glacier advances coincide with sedimentation rate minima; prior to 8800 years VT they coincide with sedimentation rate maxima. early and middle Holocene sediments suggest a periodicity of about 1000 years for cold/warm cycles.
A sequence of 512 varve-thickness measurements was subjected to spectral analysis.
These provide apparent evidence for a 11-year sun-spot cycle. from Zolitschka
Maar lake Holzmaar, Eifel

Evaporitic Varves - modern examples
Formed in saline lakes and epicontinental seas of semi-arid and arid regions when seasonal/rythmical evapotranspiration exceeds precipitation.
- evaporite minerals that may precipitate are carbonates, gypsum and halite,etc.
- depending on solubility of evaporit minerals, characteristic sequences could be formed
Sabkha-playa lake Chott el Djerid, Sahara,
Tunesia halite chips
Chott el Djerid lake Boneville/
Great Salt lake,
Northern Utah laminated siltstone/gypsum/halite
Dead Sea, Jordan

Types of evaporitic varves
Late Permian Castile Formation ~500 m thick accumulation of evaporites in west Texas and SE New Mexico
Approximate location of Castile evaporite basin
Types of Castile varves (Late Permian)
(A) Thin couplets. (B) Couplets. (C) Thick couplets.
dark laminae are calcite and admixed organic matter
light laminae are anhydrite.
(D) Triplets
laminae are anhydrite, thin beds are halite
(Kirkland 2003).

Evaporitic Varves – examples from earths history
Formed in saline lakes and epicontinental seas of semi-arid and arid regions when seasonal/rythmical evapo(transpi)ration exceeds precipitation.
- evaporite minerals that may precipitate are carbonates, gypsum and halite, etc.
- depending on solubility of evaporite minerals, characteristic sequences could be formed laminated anhydrite
Zechstein, Late Permian
Barbarossa cave,
Kyffhäuser
Interpretation:
- light layers – pure anhydrite  evaporation during dry season
- dark layers – clay rich anhydrite  sediment suppley during rainy season

mainly bio-induced
evaporation may play a role early Permian Rotliegend
Heuberg lake horizon
Friedrichroda,
Thuringian Forest basin
 indicative for semiarid seasonal climate
Interglacial calcite varves from Piànico ,
Southern Alps, Bergamo, Italy http://www.gfz-potsdam.de/portal/-
;jsessionid=44E486F3380A00C8F93A96A0A4107500?$part=C msPart&docId=1575607

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