2307223 Sedimentology Sedimentary structures Sukonmeth Jitmahantakul WEEK 5
Textbooks
Sediment pathway From Nichols (2009)
Outline 1. Introduction 2. Classification 3. Primary sedimentary structures 4. Secondary sedimentary structures
Sedimentary structures Sedimentary structures are internal megascopic features of sedimentary rocks that are best study in the field. They reflect environmental conditions that prevailed at, or very shortly after, the time of deposition. Some sedimentary structures can be used to identify the tops and bottoms of beds.
Sedimentary structures The interpretation of the origin of sedimentary structures is based on studies of their modern counterparts, on laboratory experiments and on theoretical physics.
Classification of sed. structures most common mostly chemical origin Primary structures Secondary structures weathering erosion transportation deposition diagenersis Primary structures generated in a sediment during or shortly after deposition. e.g. cross-bedding, ripples, channels, load casts Secondary structure formed sometime after sedimentation. e.g. concretions, stylolites
PRIMARY Sedimentary structures
Primary sedimentary structures (PSS) 1. Stratification & bedforms Planar bedding & lamination - Laminated bedding - Graded bedding - Massive (structureless) bedding Bedforms - Ripples - Dunes - Antidunes Cross-stratification - Cross-bedding - Ripple cross-lamination - Flaser & lenticular bedding - Herringbone cross-stratification - Hummocky cross-stratification 2. Bedding-plane marking - Groove casts, striations, bounce, brush, prod, and roll marks - Flute casts - Load casts - Tracks, trails, burrows - Mudcracks & syneresis cracks - Biogenetic structures - Pits & small impressions 3. Other structures - Sedimentary sills & dikes Irregular stratification - Convolute bedding & lamination - Flame structures - Ball & pillow structures - Synsedimentary folds and faults - Dish & pillar structures - Channels - Scour-and-fill structures - Stromatolites
Primary sedimentary structures > Stratification & bedforms > Planar bedding & lamination
Primary sedimentary structures > Stratification & bedforms > Planar bedding & lamination Laminated bedding From Nichols (2009)
Primary sedimentary structures > Stratification & bedforms > Planar bedding & lamination Graded bedding
Primary sedimentary structures > Stratification & bedforms > Planar bedding & lamination Graded bedding
Primary sedimentary structures > Stratification & bedforms > Planar bedding & lamination Massive bedding
Primary sedimentary structures > Stratification & bedforms > Bedforms
Primary sedimentary structures > Stratification & bedforms > Bedforms Ripples
Primary sedimentary structures > Stratification & bedforms > Bedforms Ripples
Primary sedimentary structures > Stratification & bedforms > Bedforms Dunes Photograph taken by Luca Zanon
Primary sedimentary structures > Stratification & bedforms > Bedforms Antidunes http://myweb.facstaff.wwu.edu/talbot/cdgeol/sediment/sedstruct2.html
Primary sedimentary structures > Stratification & bedforms > Bedforms Antidunes From Nichols (2009)
Primary sedimentary structures > Stratification & bedforms > Bedforms Antidunes
Primary sedimentary structures > Stratification & bedforms > Bedforms Antidunes
Primary sedimentary structures > Stratification & bedforms > Cross-stratification
Primary sedimentary structures > Stratification & Bedforms > Cross-stratification Cross-bedding
Primary sedimentary structures > Stratification & bedforms > Cross-stratification Cross-bedding From Nichols (2009)
Primary sedimentary structures > Stratification & bedforms > Cross-stratification Ripple cross-lamination
Primary sedimentary structures > Stratification & bedforms > Cross-stratification Flaser & lenticular bedding mixture of sand and mud variations in current or wave activity or sediment supply due to changing current strength or wave power e.g. tidal setting From Nichols (2009)
Primary sedimentary structures > Stratification & bedforms > Cross-stratification Flaser & lenticular bedding
Primary sedimentary structures > Stratification & bedforms > Cross-stratification Flaser & lenticular bedding
Primary sedimentary structures > Stratification & bedforms > Cross-stratification Herringbone cross-stratification results from a tidal current flowing predominantly in one direction for a period of time, probably many years, followed by a change in the pattern of tidal flow The herringbone pattern is characteristic of tidal sedimentation. From Nichols (2009)
Primary sedimentary structures > Stratification & Bedforms > Cross-stratification Herringbone cross-stratification
Primary sedimentary structures > Stratification & bedforms > Cross-stratification Hummocky cross-stratification occur in offshore transition zone (shallow marine) where sands are deposited and reworked by storms. - Storm deposits consisting of rounded mounds of sand on the sea floor a few centimetres high and tens of centimetres across convex upward, dips in all directions at low angles, and thickness laterally concave layers = Swaley cross-stratification The environment where hummocky and swaley cross-stratification form is yet another source of debate. From Nichols (2009)
Primary sedimentary structures > Stratification & bedforms > Cross-stratification Depositional model for HCS & SCS A: Fair-weather conditions. Sediment transport is shoreward with short-period, low oscillatory velocity affecting bottom from shoreline to fair-weather wave base. B: Storm conditions. From Dumas & Arnott (2006) Sediment transport is basinward with long-period, high oscillatory velocity waves affecting bottom from shoreline to storm wave base. From Nichols (2009)
Primary sedimentary structures > Stratification & bedforms > Cross-stratification Hummocky cross-stratification Gary Nichols : Sedimentology and Stratigraphy
Primary sedimentary structures > Stratification & bedforms > Cross-stratification Hummocky cross-stratification Gary Nichols : Sedimentology and Stratigraphy
Primary sedimentary structures > Stratification & bedforms > Irregular stratification
Primary sedimentary structures > Stratification & Bedforms > Irregular stratification Convolute bedding & lamination The layering within sediments can be disrupted during or after deposition by localised and small-scale liquefaction of the material. The structures range from slight overstepping of cross-strata to the development of highly folded and contorted layers. Either deposited on slight slope or where there is a shear stress on the material due to flow of overlying fluid. Convolute lamination is particularly common in turbidites. From Nichols (2009)
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Convolute bedding & lamination
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Convolute bedding & lamination
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Convolute bedding & lamination
Primary sedimentary structures > Stratification & Bedforms > Irregular stratification Load cast & flame structures form where higher density sand has partially sunk into the underlying mud to form downward-facing, bulbous structures The mud may become forced up into the overlying sand bed to form a flame structure. Ball-and-pillow structure mud From Nichols (2009)
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Flame structures
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Load cast
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Load cast & flame structures Gary Nichols : Sedimentology and Stratigraphy
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Ball & pillow structures Photograph taken by Rygel, M.C.
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Diapirism form where the instability due to density differences between layers of unconsolidated sediment results in movements of material on a large scale. most commonly observed where the density contrast is large and the low-density material is relatively mobile From Nichols (2009)
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Diapirism http://sepwww.stanford.edu/sep/jon/crustal/
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Synsedimentary folds & faults a result of gravitational instabilities in sediment piles
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Synsedimentary folds & faults
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Synsedimentary folds & faults
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Synsedimentary folds & faults Gary Nichols : Sedimentology and Stratigraphy
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Dish & pillar structures Photograph taken by Rudolf Pohl
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Dish & pillar structures Photograph taken by Rudolf Pohl
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Dish & pillar structures Evolution of dish structure in and adjacent to small anticlinal convolution. From Lowe & LoPiccolo (1974)
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Liquefaction
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Channels Channel confines the flow. size range from features less than a metre deep and only metres across to large-scale structures many tens of metres deep and kilometres to tens of kilometres in width. occur in diverse environments ranging from subaerial alluvial plains to submarine continental margins can be petroleum reservoirs and aquifers contain placer and replacement mineral ore bodies cut out coal seams
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Channels Image credit: Callan from blogs.agu.org
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Channels
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Channels Pringle et al 2010
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Scour-and-fill structures
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Stromatolites Photograph taken by Rygel, M.C.
Primary sedimentary structures > Stratification & bedforms > Irregular stratification Stromatolites http://www.nsf.gov/news/mmg/media/images/stromatolite1_h.jpg
Primary sedimentary structures > Bedding-plane markings
Primary sedimentary structures > Bedding-plane markings Cast & mould occur on surfaces between beds formed before the deposition of the overlying bed Cast Mould
Primary sedimentary structures > Bedding-plane markings Sole marks Small-scale erosional features on a bed surface found in a very wide range of depositional environments, but common in successions of turbidites Scour marks are negative relief features produced as a result of erosion of a sediment surface by the current flowing over it, formed via the impingement of usually sediment-laden eddies on beds. Tool marks - impression formed by object carried in the water flow
Primary sedimentary structures > Bedding-plane markings Scour marks asymmetric in cross-section with one steep edge opposite a tapered edge In plan view, they are narrower at one end, widening out onto the tapered edge wider edge marks the passage of the eddy as it is swept away by the current. can be used as palaeocurrent indicators From Nichols (2009)
Primary sedimentary structures > Bedding-plane markings Flute mark Image credit Christopher Spencer from travellinggeologist.com
Primary sedimentary structures > Bedding-plane markings Flute mark Image credit Christopher Spencer from travellinggeologist.com
Primary sedimentary structures > Bedding-plane markings Obstacle scours Gary Nichols : Sedimentology and Stratigraphy
Primary sedimentary structures > Bedding-plane markings Tool marks sharply defied elongate marks created by an object (tool) being dragged along the bed often seen in lines along the bedding plane The shape and size of all tool marks is determined by the form of the object From Nichols (2009)
Primary sedimentary structures > Bedding-plane markings Groove marks Gary Nichols : Sedimentology and Stratigraphy
Primary sedimentary structures > Bedding-plane markings Groove marks Gary Nichols : Sedimentology and Stratigraphy
Primary sedimentary structures > Bedding-plane markings Mudcracks caused by subaerial desiccation of mud a broader spacing occurs in thicker deposits In cross-section desiccation cracks taper downwards and the upper edges may roll up mud-chips, mud-flakes Gary Nichols : Sedimentology and Stratigraphy
Primary sedimentary structures > Bedding-plane markings Desiccation cracks Gary Nichols : Sedimentology and Stratigraphy
Primary sedimentary structures > Bedding-plane markings Syneresis cracks Gary Nichols : Sedimentology and Stratigraphy
Primary sedimentary structures > Bedding-plane markings Biogenetic structures One of the basic principles of trace fossil analysis is that similar ichnogenera can be produced by a wide variety of organisms. The shape of a trace fossil reflects environment rather than creator. Trace fossils always occur in place and cannot be reworked like most other fossils. Ichnofossils have been grouped according to the activity which made them and according to their topology.
Primary sedimentary structures > Bedding-plane marking Ichnology Plant rootlets Vertebrate footprints (tracks) Trails Soft sediment burrows Hard rock borings Study of trace fossils = Ichnology Gary Nichols : Sedimentology and Stratigraphy
Primary sedimentary structures > Bedding-plane markings Bioturbation The presence of evidence of organisms disturbing sediment very common feature in sedimentary rocks the absence of bioturbation in shallow marine deposits may be taken as an indicator of something unusual about conditions - anoxic sea floor. the intensity of bioturbation in a body of sediment is an indication of the number of animals living there and the length of time over which they were active
Primary sedimentary structures > Bedding-plane markings Ichnofacies The broad correlation between depositional environment and characteristic trace fossil assemblages. From Nichols (2009)
Primary sedimentary structures > Bedding-plane markings Burrows
Primary sedimentary structures > Bedding-plane markings Burrows Crab burrow in a modern sandy beach.
Primary sedimentary structures > Bedding-plane markings Complex burrows Gary Nichols : Sedimentology and Stratigraphy
Primary sedimentary structures > Bedding-plane markings Complex burrows Gary Nichols : Sedimentology and Stratigraphy
Primary sedimentary structures > Bedding-plane markings Zoophycos Gary Nichols : Sedimentology and Stratigraphy
Primary sedimentary structures > Bedding-plane markings Palaeodictyon Gary Nichols : Sedimentology and Stratigraphy
Primary sedimentary structures > Bedding-plane markings Helminthoidea Gary Nichols : Sedimentology and Stratigraphy
PSS - depositional structures 1. Stratification & bedforms Planar bedding & lamination - Laminated bedding (A, B, C) - Graded bedding (A) - Massive (structureless) bedding (A) Bedforms - Ripples (A, B) - Dunes (A, B) - Antidunes (A) 2. Bedding-plane marking - Groove casts, striations, bounce, brush, prod, and roll marks - Flute casts - Load casts - Tracks, trails, burrows - Mudcracks & syneresis cracks - Pits & small impressions Cross-stratification - Cross-bedding (A, B) - Ripple cross-lamination (A, B) - Flaser & lenticular bedding (A) - Herringbone cross-stratification (A) - Hummocky cross-stratification (A) 3. Other structures - Sedimentary sills & dikes Irregular stratification - Convolute bedding & lamination - Flame structures - Ball & pillow structures - Synsedimentary folds and faults - Dish & pillar structures - Channels - Scour-and-fill structures - Stromatolites A.Suspension settling & current- and waved-formed structures B.Wind-formed structures C.Chemically & biochemicallly formed structures
PSS - erosional structures 1. Stratification & bedforms Planar bedding & lamination - Laminated bedding - Graded bedding - Massive (structureless) bedding Bedforms - Ripples - Dunes - Antidunes 2. Bedding-plane marking - Groove casts, striations, bounce, brush, prod, and roll marks (E) - Flute casts (E) - Load casts - Tracks, trails, burrows - Mudcracks & syneresis cracks - Pits & small impressions Cross-stratification - Cross-bedding - Ripple cross-lamination - Flaser & lenticular bedding - Herringbone cross-stratification - Hummocky cross-stratification Irregular stratification - Convolute bedding & lamination - Flame structures - Ball & pillow structures - Synsedimentary folds and faults - Dish & pillar structures - Channels (D) - Scour-and-fill structures (D) - Stromatolites 3. Other structures - Sedimentary sills & dikes D. Scour marks E. Tool marks
PSS - deformation structures 1. Stratification & bedforms Planar bedding & lamination - Laminated bedding - Graded bedding - Massive (structureless) bedding Bedforms - Ripples - Dunes - Antidunes 2. Bedding-plane marking - Groove casts, striations, bounce, brush, prod, and roll marks - Flute casts - Load casts (G) - Tracks, trails, burrows - Mudcracks & syneresis cracks (J) - Pits & small impressions (K) Cross-stratification - Cross-bedding - Ripple cross-lamination - Flaser & lenticular bedding - Herringbone cross-stratification - Hummocky cross-stratification Irregular stratification - Convolute bedding & lamination (G) - Flame structures (G) - Ball & pillow structures (G) - Synsedimentary folds and faults (F) - Dish & pillar structures (I) - Channels - Scour-and-fill structures - Stromatolites 3. Other structures - Sedimentary sills & dikes (H) F. Slump structures G. Load & founder structures H. Injection structures I. Fluid-escape structures J. Desiccation structures K. Impact structures
PSS - biogenic structures 1. Stratification & bedforms Planar bedding & lamination - Laminated bedding - Graded bedding - Massive (structureless) bedding Bedforms - Ripples - Dunes - Antidunes Cross-stratification - Cross-bedding - Ripple cross-lamination - Flaser & lenticular bedding - Herringbone cross-stratification - Hummocky cross-stratification Irregular stratification - Convolute bedding & lamination - Flame structures - Ball & pillow structures - Synsedimentary folds and faults - Dish & pillar structures - Channels - Scour-and-fill structures - Stromatolites (M) 2. Bedding-plane marking - Groove casts, striations, bounce, brush, prod, and roll marks - Flute casts - Load casts - Tracks, trails, burrows (L) - Mudcracks & syneresis cracks - Pits & small impressions 3. Other structures - Sedimentary sills & dikes (H) L. Bioturbation structures M. Biostratification structures
SECONDARY Sedimentary structures
Secondary sedimentary structures Concretions
Secondary sedimentary structures Stylolites