普通地质学(英文).ppt

1、SEDIMENTARY ARCHIVES,Sedimentary Structures Cross-bedding or Cross-stratification,SEDIMENTARY ARCHIVES,Sedimentary Structures Cross-bedding or Cross-stratification Beds in which one set is inclined to others Advance of delta or dunes Current dominated environment Wind or water Slope of cross-bed can

2、 indicates current or prevailing wind direction,SEDIMENTARY ARCHIVES,Sedimentary Structures Cross-bedding or Cross-stratification,Tabular or Planar,SEDIMENTARY ARCHIVES,Sedimentary Structures Cross-bedding or Cross-stratification,Trough,SEDIMENTARY ARCHIVES,Sedimentary Structures Graded beds,SEDIMEN

3、TARY ARCHIVES,Sedimentary Structures Sole marks,SEDIMENTARY ARCHIVES,Sedimentary Structures Flute casts,SEDIMENTARY ARCHIVES,Sedimentary Structures Tool marks,SEDIMENTARY ARCHIVES,Sedimentary Structures Flame Structures,SEDIMENTARY ARCHIVES,Sedimentary Structures Geopetal Structures or Which Way is

4、UP? Load structures,SEDIMENTARY ARCHIVES,Sedimentary Structures Geopetal Structures or Which Way is UP? Mudcracks,SEDIMENTARY ARCHIVES,Sedimentary Structures Geopetal Structures or Which Way is UP? Planar Cross-beds,SEDIMENTARY ARCHIVES,Sedimentary Structures Geopetal Structures or Which Way is UP?

5、Trough Cross-beds,SEDIMENTARY ARCHIVES,Sedimentary Structures Geopetal Structures or Which Way is UP? Oscillation ripples,SEDIMENTARY ARCHIVES,Sedimentary Structures Geopetal Structures or Which Way is UP? Tool marks,SEDIMENTARY ARCHIVES,Sedimentary Structures Geopetal Structures or Which Way is UP?

6、 Fossils,SEDIMENTARY ARCHIVES,Sedimentary Structures Geopetal Structures or Which Way is UP? Fossils,SEDIMENTARY ARCHIVES,Sedimentary Structures Geopetal Structures or Which Way is UP? Raindrop Impressions,SEDIMENTARY ARCHIVES,Interpretation of Sedimentary Rocks Provide information about conditions

7、in and near the site of deposition Such as:source area from composition amount of transport erosion Qtz vs. Feldspar (clay and iron compounds) vs Ferromagnesians Immature vs mature,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,Systems of classification are not hatracks, objectively presen

8、ted to us by nature. They are dynamic theories developed to express particular views. Stephen Jay Gould,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,TEXTURE,SEDIMENTARY ARCHI

9、VES,Classification of Sedimentary Rocks,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,Quartz Arenite,90% Quartz Cement: silica calcite,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,Feldspathic Arenite Arkose,25% Feldspar Granitic source Remainder is quartz Cement: clay calcite

10、iron oxides,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,Lithic Arenite Greywacke,33% rock fragments Immature sandstone Poorly sorted, angular Remainder is quartz, feldspar Cement: very little mostly clays,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,Composition Carbonate roc

11、ks consist of limestone and dolostone. The minerals present in each are: Limestone Calcite Aragonite Dolostone Dolomite,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,Carbonates,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,Carbonates Most of marine origin Directly or indirectly

12、 related to biological processes Skeletal remains may be visible Can be evaporites Changes in water temp., alkalinity, CO2 conc. Clear, shallow tropical waters,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,Carbonates Characteristics of most marine carbonate environments: Warm water Tropic

13、al climate (30 N - 30 S of equator) Shallow water (less than 200 m deep) Clear water (low to no terrigenous input) Sunlight required for photosynthesis by algae,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,Carbonates,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,Carbonates Ori

14、gin of carbonate sediments Much lime mud forms from the disintegration of calcareous algae (such as Halimeda and Penicillus). When the calcareous algae die, their skeletons break down and disintegrate producing aragonite needle muds. These lime muds lithify to form fine-grained limestone.,SEDIMENTAR

15、Y ARCHIVES,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,Carbonates Fossiliferous limestone Biomicrite Biosparite,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,Carbonates Oolitic limestone Oomicrite Oosparite,SEDIMENTARY ARCHIVES,Classification of Sedimentary Rocks,Carbonates D

16、olostone Composed of dolomite (CaMg(CO3)2) The Dolomite “Problem” Dolomite is believed to form when magnesium that has been concentrated in sea water replaces calcium carbonate in a previously deposited limestone. Today, dolomite only forms in a few areas of the world where intense evaporation of se

17、awater concentrates the magnesium. Extensive areas of carbonate rocks of Precambrian, Paleozoic, and Mesozoic age have been altered to dolomite. Dolomitization may be related to times of high sea level worldwide, under favorable climatic conditions.,SEDIMENTARY ARCHIVES,Classification of Sedimentary

18、 Rocks,Clays, Mudrocks and Shales Mudrocks are a very fine-grained Composed of clay and silt-sized particles If the mudrock is fissile it is a -shale Typically form in low energy environments,SEDIMENTARY ARCHIVES,Sea Level Changes,Eustatic Sea Level Change Global change in sea level position Caused

19、by:Glacial advance and retreat Change in spreading rates Effect lowland areas,SEDIMENTARY ARCHIVES,Sea Level Changes,Sequence Stratigraphy Epeiric seas Seas covered continents Produced packages called sequences Led to sequence stratigraphy,SEDIMENTARY ARCHIVES,Sea Level ChangesSequence Stratigraphy,

20、Sequence Stratigraphy A group of relatively conformable strata that represents a cycle of deposition and is bounded by unconformities or correlative conformities. Sequences are the fundamental unit of interpretation in sequence stratigraphy. Sequences comprise systems tracts.,SEDIMENTARY ARCHIVES,Se

21、a Level Changes,SEDIMENTARY ARCHIVES,Sea Level Changes,Vail Curve,Sequence Stratigraphy,SEDIMENTARY ARCHIVES,Sea Level Changes,/clastic-movie.html,SEDIMENTARY ARCHIVES,Sea Level Changes,Sequence Stratigraphy,THE FOSSIL RECORD,Paleontology,Attempts to understand all aspects of the succession of plants and animals over time. Based on study of fossils,Archaeopteryx,THE FOSSIL RECORD,Paleontology,Fossil Preservation Cover this aspect in lab