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Figure 8-20: Schematic dip profile showing the key sequence-stratigraphic surfaces. Dark 10.3.5 Recall that I mentioned earlier that there can be several distinct orders of sea-level cyclicity, from as short as centuries or millennia to as long as tens of millions of years. For that reason, one often has to deal with sedimentary successions deposited during more than one order of sea-level cycle. the result is: thinner and shorter-term sequences superimposed on thicker and longer-term sequences! In particular, the term parasequence is used for the shortest-period and thinnest such cycles, typically with thicknesses on the scale of one to a few meters, which are superposed on thicker sequences that may be tens to a hundred meters thick.

Figure 8 -20: Schematic dip profile showing the key sequence-stratigraphic surfaces. Dark 10.3.5 Recall that I mentioned earlier that there can be several distinct orders of sea-level cyclicity, from as short as centuries or millennia to as long as tens of millions of years. For that reason, one often has to deal with sedimentary successions deposited during more than one order of sea-level cycle. the result is: thinner and shorter-term sequences superimposed on thicker and longer-term sequences! In particular, the term parasequence is used for the shortest-period and thinnest such cycles, typically with thicknesses on the scale of one to a few meters, which are superposed on thicker sequences that may be tens to a hundred meters thick.

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6.3 Common within conformable sedimentary sequences are disconformities—surfaces representing breaks in time without any discordance of strata. Disconformities represent temporary cessation of deposition, and these nondepositional episodes may or may not be accompanied by erosion of the preexisting sediment. Where there is erosion of the underlying sediment the disconformity is said to be an erosional disconformity. If there is no erosion, the presence of the disconformity is difficult or impossible to detect. The break or zap in time represented by a disconformity is called a hiatus or a diastem.
6.3 Common within conformable sedimentary sequences are disconformities—surfaces representing breaks in time without any discordance of strata. Disconformities represent temporary cessation of deposition, and these nondepositional episodes may or may not be accompanied by erosion of the preexisting sediment. Where there is erosion of the underlying sediment the disconformity is said to be an erosional disconformity. If there is no erosion, the presence of the disconformity is difficult or impossible to detect. The break or zap in time represented by a disconformity is called a hiatus or a diastem.
Figure 8-12. A disconformity involving both erosion and change in sediment type.
Figure 8-12. A disconformity involving both erosion and change in sediment type.
Figure 8-14: Cross section normal to a shoreline, to illustrate the effect of cyclic fluctuation. s in sea level on sediment deposition
Figure 8-14: Cross section normal to a shoreline, to illustrate the effect of cyclic fluctuation. s in sea level on sediment deposition
10.2.3 Several kinds of relationships of sedimentary layers are characteristic of seismic reflection profiles (Figure 8-19). A clinoform is an inclined surface, reflecting the sloping seafloor (or lake floor!) on which a body of strata is deposited. The usual interpretation of clinoform is that they represent the progradation geometry of sediment packages that build out into deeper water. Also commonly seen on seismic sections are unconformities, about which you learned earlier in this chapter. Unconformities usually involve actual erosional truncation.
10.2.3 Several kinds of relationships of sedimentary layers are characteristic of seismic reflection profiles (Figure 8-19). A clinoform is an inclined surface, reflecting the sloping seafloor (or lake floor!) on which a body of strata is deposited. The usual interpretation of clinoform is that they represent the progradation geometry of sediment packages that build out into deeper water. Also commonly seen on seismic sections are unconformities, about which you learned earlier in this chapter. Unconformities usually involve actual erosional truncation.
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