沉积构造(Sedimentary-structures)-英文课件

1、沉积构造(Sedimentary-structures)-英文,1,Contents,Introduction Unconsolidated clastic sediments Sedimentary rocks Diagenesis Sediment transport and deposition Sedimentary structures Facies and depositional environments Glacial/eolian/lacustrine environments Fluvial/deltaic/coastal environments Shallow/deep

2、 marine environments,Stratigraphic principles Sequence stratigraphy Sedimentary basins Models in sedimentary geology Applied sedimentary geology Reflection,沉积构造(Sedimentary-structures)-英文,2,Sedimentary structures,Sedimentary structures occur at very different scales, from less than a mm (thin sectio

3、n) to 100s1000s of meters (large outcrops); most attention is traditionally focused on the bedform-scale Microforms (e.g., ripples) Mesoforms (e.g., dunes) Macroforms (e.g., bars),沉积构造(Sedimentary-structures)-英文,3,沉积构造(Sedimentary-structures)-英文,4,沉积构造(Sedimentary-structures)-英文,5,Sedimentary struct

4、ures,Laminae and beds are the basic sedimentary units that produce stratification; the transition between the two is arbitrarily set at 10 mm Normal grading is an upward decreasing grain size within a single lamina or bed (associated with a decrease in flow velocity), as opposed to reverse grading F

5、ining-upward successions and coarsening-upward successions are the products of vertically stacked individual beds,沉积构造(Sedimentary-structures)-英文,6,沉积构造(Sedimentary-structures)-英文,7,Animation,沉积构造(Sedimentary-structures)-英文,8,Animation,沉积构造(Sedimentary-structures)-英文,9,Sedimentary structures,Cross s

6、tratification Cross lamination (small-scale cross stratification) is produced by ripples Cross bedding (large-scale cross stratification) is produced by dunes Cross-stratified deposits can only be preserved when a bedform is not entirely eroded by the subsequent bedform (i.e., sediment input sedimen

7、t output) Straight-crested bedforms lead to planar cross stratification; sinuous or linguoid bedforms produce trough cross stratification,沉积构造(Sedimentary-structures)-英文,10,沉积构造(Sedimentary-structures)-英文,11,沉积构造(Sedimentary-structures)-英文,12,沉积构造(Sedimentary-structures)-英文,13,沉积构造(Sedimentary-struc

8、tures)-英文,14,沉积构造(Sedimentary-structures)-英文,15,沉积构造(Sedimentary-structures)-英文,16,沉积构造(Sedimentary-structures)-英文,17,沉积构造(Sedimentary-structures)-英文,18,沉积构造(Sedimentary-structures)-英文,19,Sedimentary structures,Cross stratification The angle of climb of cross-stratified deposits increases with depos

9、ition rate, resulting in climbing ripple cross lamination Antidunes form cross strata that dip upstream, but these are not commonly preserved A single unit of cross-stratified material is known as a set; a succession of sets forms a co-set,沉积构造(Sedimentary-structures)-英文,20,沉积构造(Sedimentary-structur

10、es)-英文,21,Sedimentary structures,Planar stratification Planar lamination (or planar bedding) is formed under both lower-stage and upper-stage flow conditions Planar stratification can easily be confused with planar cross stratification, depending on the orientation of a section (strike sections!),沉积

11、构造(Sedimentary-structures)-英文,22,沉积构造(Sedimentary-structures)-英文,23,沉积构造(Sedimentary-structures)-英文,24,沉积构造(Sedimentary-structures)-英文,25,沉积构造(Sedimentary-structures)-英文,26,Sedimentary structures,Cross stratification produced by wave ripples can be distinguished from current ripples by their symmetr

12、y and by laminae dipping in two directions Hummocky cross stratification (HCS) forms during storm events with combined wave and current activity in shallow seas (below the fair-weather wave base), and is the result of aggradation of mounds and swales Heterolithic stratification is characterized by a

13、lternating sand and mud laminae or beds Flaser bedding is dominated by sand with isolated, thin mud drapes Lenticular bedding is mud-dominated with isolated ripples,沉积构造(Sedimentary-structures)-英文,27,沉积构造(Sedimentary-structures)-英文,28,沉积构造(Sedimentary-structures)-英文,29,沉积构造(Sedimentary-structures)-英

14、文,30,Sedimentary structures,Cross stratification produced by wave ripples can be distinguished from current ripples by their symmetry and by laminae dipping in two directions Hummocky cross stratification (HCS) forms during storm events with combined wave and current activity in shallow seas (below

15、the fair-weather wave base), and is the result of aggradation of mounds and swales Heterolithic stratification is characterized by alternating sand and mud laminae or beds Flaser bedding is dominated by sand with isolated, thin mud drapes Lenticular bedding is mud-dominated with isolated ripples,沉积构

16、造(Sedimentary-structures)-英文,31,沉积构造(Sedimentary-structures)-英文,32,沉积构造(Sedimentary-structures)-英文,33,Sedimentary structures,Tide-influenced sedimentary structures can take different shapes: Herringbone cross stratification indicates bipolar flow directions, but are rare Mud-draped cross strata are

17、much more common, and are the result of alternating bedform migration during high flow velocities and mud deposition during high or low tide (slackwater) Tidal bundles are characterized by a sand-mud couplet with varying thickness; tidal bundle sequences consist of a series of bundles that can be re

18、lated to neap-spring cycles,沉积构造(Sedimentary-structures)-英文,34,Sedimentary structures,Gravity-flow deposits Debris-flow deposits are typically poorly sorted, matrix-supported sediments with random clast orientation and no sedimentary structures; thickness and grain size commonly remain unchanged in

19、a proximal to distal direction Turbidites, the deposits formed by turbidity currents, are typically normally graded, ideally composed of five units (Bouma-sequence with divisions a-e), reflecting decreasing flow velocities and associated bedforms,沉积构造(Sedimentary-structures)-英文,35,沉积构造(Sedimentary-s

20、tructures)-英文,36,Sedimentary structures,Gravity-flow deposits Debris-flow deposits are typically poorly sorted, matrix-supported sediments with random clast orientation and no sedimentary structures; thickness and grain size commonly remain unchanged in a proximal to distal direction Turbidites, the

21、 deposits formed by turbidity currents, are typically normally graded, ideally composed of five units (Bouma-sequence with divisions a-e), reflecting decreasing flow velocities and associated bedforms,沉积构造(Sedimentary-structures)-英文,37,沉积构造(Sedimentary-structures)-英文,38,沉积构造(Sedimentary-structures)-

22、英文,39,Sedimentary structures,Imbrication commonly occurs in water-lain gravels and conglomerates, and is characterized by discoid (flat) clasts consistently dipping upstream Sole marks are erosional sedimentary structures on a bed surface that have been preserved by subsequent burial Scour marks (ca

23、used by erosive turbulence) Tool marks (caused by imprints of objects) Paleocurrent measurements can be based on any sedimentary structure indicating a current direction (e.g., cross stratification, imbrication, flute casts),沉积构造(Sedimentary-structures)-英文,40,沉积构造(Sedimentary-structures)-英文,41,Sedim

24、entary structures,Imbrication commonly occurs in water-lain gravels and conglomerates, and is characterized by discoid (flat) clasts consistently dipping upstream Sole marks are erosional sedimentary structures on a bed surface that have been preserved by subsequent burial Scour marks (caused by ero

25、sive turbulence) Tool marks (caused by imprints of objects) Paleocurrent measurements can be based on any sedimentary structure indicating a current direction (e.g., cross stratification, imbrication, flute casts),沉积构造(Sedimentary-structures)-英文,42,沉积构造(Sedimentary-structures)-英文,43,Sedimentary stru

26、ctures,Imbrication commonly occurs in water-lain gravels and conglomerates, and is characterized by discoid (flat) clasts consistently dipping upstream Sole marks are erosional sedimentary structures on a bed surface that have been preserved by subsequent burial Scour marks (caused by erosive turbul

27、ence) Tool marks (caused by imprints of objects) Paleocurrent measurements can be based on any sedimentary structure indicating a current direction (e.g., cross stratification, imbrication, flute casts),沉积构造(Sedimentary-structures)-英文,44,沉积构造(Sedimentary-structures)-英文,45,沉积构造(Sedimentary-structures)-英文,46,Sedimentary structures,Trace fossils (ichnofossils) are the tracks, trails or burrows left behi