Ch9_ Tidal Flat Depositional System

8/9/2019 Ch9_ Tidal Flat Depositional System

1/41

TIDAL FLAT DEPOSITIONAL SYSTEM

Tide dominated shallow seas are common in many parts of the world

The tide dominated sedimentation can !e identified into three distinct

domains

Tidal flats

Tidal shoals

Tidal c"rrent rid#es

Tides ca"se periodic rise and fall of the water le$el% which may !e

semidi"rnal &' tides a day( or di"rnal &) tide a day( Tides areidentified into sprin#*neap cycles

Tidal ran#e increases in the em!ayments and !ays &)+*),m( -owe$er%

in open sea tidal ran#e is small &a!o"t ,+cm(


2/41


3/41


4/41


5/41


6/41

Tidal flat deposits

Tidal flats are #entle slopin# sea coast with mar.ed tidal rhythm and

low wa$e ener#y They occ"r with est"aries% !ays% !ac. !arrier/

sometimes on open sea

Tidal flats are identified into s"pratidal% intertidal and s"!tidal

0ones On the intertidal 0one hi#hly meanderin# channels are

common

1elocity on the tidal flats is "s"ally 2+*,+cm3s% in the tidal channels

it is )*),m3s

S"pratidal 0one is de$eloped as salt marsh

Intertidal 0one shows m"d near -4L &m"d flat(% followed !y mi5ed

flat% and sand near L4L &sand flat(


7/41


8/41


9/41


10/41


11/41


12/41


13/41


14/41


15/41

Supratidal zone show deposition of rooted m"d with crin.led

lamination

Mud flat is made "p of m"d layers with millimeter thin sand layers/

mixed flate5hi!its lentic"lar*flaser !eddin#% tidal !eddin#/ sand flat

shows small ripple !eddin#% flaser !eddin#% hori0ontal !eddin#

The tidal creeks of intertidal 0one show lon#it"dinal cross*!eddin#

&Epsilon cross*stratification(

S"!tidal 0one shows lar#e*scale cross*!eddin# and coarse*#rained

sediments

Tidal flat deposits are characteri0ed !y n"mero"s erosional contacts%

a!r"pt $ertical and hori0ontal chan#es in !eddin# str"ct"res% rarity of

macrose6"ences


16/41


17/41

Tidal shoals

The shallow shelf of tidal sea shows de$elopment of lar#e sandy

areas as sandy shoals and channels

Tidal shoals are formed mainly !y tidal c"rrents with s"!ordinate role

of wa$es The shoals e5tend from s"!tidal 0one to intertidal 0one

They show prominent de$elopment of lar#e !ed forms

The tidal shoal*channel comple5 prod"ce se$eral meter thic. sanddeposits showin# lar#e*scale cross*!eddin# in lower part/ small

ripple !eddin# and laminated sand in the "pper part


18/41


19/41


20/41


21/41


22/41


23/41


24/41


25/41


26/41


27/41


28/41


29/41


30/41


31/41


32/41


33/41

Tidal feat"res in shoal deposits

Tidal shoals and s"!tidal channels e5hi!it few distincti$e feat"res in the

cross !eddin#

Tidal !"ndles

A tidal !"ndle is a set of cross strata% laterally enclosed !y pa"se planes

Three distinct parts are% reactivation structures% full vortex structuresand

slackening structures It is followed !y s"!ordinate tide str"ct"res% which

may incl"de double mud drape

Neap*sprin# tide cycle

In a cross*stratified "nit tidal !"ndles show increase in hei#ht and an#le

of foresets d"rin# neap to sprin#/ and #rad"al decrease in hei#ht and

an#le of foresets d"rin# sprin# to neap '7 tidal !"ndles can !e identified

in a neap*sprin#*neap cycle


34/41

Tidal 8"rrent 9id#es

In tide*dominated continental shel$es% with the a$aila!ility of sand

linear rid#es parallel to c"rrent direction are present

These rid#es occ"r in #ro"ps% ha$in# len#th of tens of .ilometers%

width few .ilometers and hei#ht tens of meters Lar#e !edforms mo$e

o$er the tidal rid#es

Tidal rid#es show lar#e*scale cross !eddin# with some m"d layers

They may represent trans#ressi$e sand deposits of a tide dominated

shelf


35/41


36/41


37/41


38/41


39/41


40/41


41/41

Documents

Ch9_ Tidal Flat Depositional System