Parasequence

Walther's Law

Figure 5 above is associated with the exercises on high frequency clastic parasequences. Note the hierarchy of sedimentary structures and their association, from seaward to landward, with the different depositional systems that are listed in Table below. The vertical and lateral relationships seen here are intended to demonstrate the basis of Walther's Law.

Setting	Relationship to Waves & Tide	Sedimentary Structures
Coastal Plain	Tidal zone, subject to storm wash-over	Trough-cross bedded fill of tidal inlet, estuarine & fluvial channels Rooted seat earths & coals
Foreshore & upper shoreface	Zone of breaking waves & the wave swash zone	Trough-cross stratified sandstone sometimes overlain by planar-cross bedded sandstone
Lower shoreface & delta-front sandstones	Just above fair-weather wave base	Current ripple beds Wave ripple beds, Hummocky cross-beds Contorted beds
Transition between offshore shelf & lower shore-face	Between storm wave-base & fair-weather wave-base	Alternations of hummocky cross-stratified sandstone Highly burrowed silty mudstones
Offshore shelf	Below storm wave-base	Highly burrowed mudstones

 

 

 

 

 

 

 

The table shows the relationship between the sediments of a clastic shoreline depositional setting to tide & waves, and sedimentary structures.