300
Chapter 7 Sequences, Minor Cycles, and Event StratigraphY
Table 7.2. Definitions and terms describing architectural elements of sedimentary sequences
(for more details see text)
Aggradation,
pro gradation,
backstepping
Sequence
stratigraphy
S tratigraphic (or
genetic sequence)
Allostratigraphy,
allomember
(Fig.7.3d)
Sequence
boundaries
(Fig.7.3f)
System tracts or
facies tract
(Fig. 7.3g and h)
Parasequences,
parasequence,
sets
Transßl:ession or
regressIOn
Marine flooding
surface
Transgressive
surface, TS
Maximum
flooding surface,
MFS
Condensed
section, CS
Coastal onlap,
offlap, downlap
Terms to describe the different modes of the growth of sedimentary bodies in relation
to the basin geometry (stratal patterns, Fig. 7.3e)
Study of sedimentary facies relationships within a chronostratigraphic framework of
repetitive, genetically related strata
The sedimentary sequence produced by one full cycle of sea-Ievel or base-level change
is the fundamental unit in sequence stratigraphy. It is bounded by one or two types of
sequence boundaries (SB)
An allostratigraphic unit or allomember is a facies tract which is commonly not
bounded by time lines (isochrones). It often comprises different types of facies and its
isochrones may run obliquely through individual facies zones. In sequence stratigraphy, an allomember may describe a parasequence or a systems tract bounded by
diachronous erosional or transgressive surfaces
A Type I sequence boundary (SB!) is an erosional unconformity. It represents a stratigraphic gap (hiatus) of differing duration caused by subaerial and/or sub-marine erosion. This boundary is mostly diachronous and tends to become younger basinward
where it passes into a Type 2 sequence boundary (SB2). This boundary is a "correlative conformity"
System tracts are subunits of depositional sequences: lowstand systems tract LST,
transgressive systems tract TST, highstand systems tract HST, and shelf margin systems tract SMST
Systems tracts can be subdivided into smaller, commonly shallowing-upward units
called parasequences bounded by marine flooding surfaces (see below) which are assumed to be isochrones
Landward or basinward shifting of the coastline (and depocenter of sedimentation
(prograding and backstepping)
Diachronous surface indicating minor submarine erosion (no subaerial erosion) and
separating strata of shallower environment (bottom) from deposits of deeper environment (top). Correlative, less distinct surfaces m3Y exist on the coastal plain and the
shelf
This surface is the first significant marine flooding surface on top of the lowstand systems tract
This ± isochronous surface forms at the transition from TST to HST and reaches maximum landward extent. The toes of prograding HST clinoforms downlap onto this surface (downlap surface)
Thin unit of hemipelagic to pelagic marine sediments deposited in a relatively distal
basin position during the late TST and early HST
S tratal termination patterns in seismic stratigraphy (F ig. 7.3 f)
Eustasy, EU, signifies coeval global sea-Ievel
change which is controlled by two principal factors:
change in the volume of the ocean basins (tectonoeustasy) and/or change in the water volume of the
oceans (glacio-eustasy). The volume of the ocean
basins mainly results from the age and distribution of
continental and oceanic crust, i.e. plate tectonic proces ses. The ocean water volume changes with the
Chapter 7 Sequences, Minor Cycles, and Event StratigraphY
Table 7.2. Definitions and terms describing architectural elements of sedimentary sequences
(for more details see text)
Aggradation,
pro gradation,
backstepping
Sequence
stratigraphy
S tratigraphic (or
genetic sequence)
Allostratigraphy,
allomember
(Fig.7.3d)
Sequence
boundaries
(Fig.7.3f)
System tracts or
facies tract
(Fig. 7.3g and h)
Parasequences,
parasequence,
sets
Transßl:ession or
regressIOn
Marine flooding
surface
Transgressive
surface, TS
Maximum
flooding surface,
MFS
Condensed
section, CS
Coastal onlap,
offlap, downlap
Terms to describe the different modes of the growth of sedimentary bodies in relation
to the basin geometry (stratal patterns, Fig. 7.3e)
Study of sedimentary facies relationships within a chronostratigraphic framework of
repetitive, genetically related strata
The sedimentary sequence produced by one full cycle of sea-Ievel or base-level change
is the fundamental unit in sequence stratigraphy. It is bounded by one or two types of
sequence boundaries (SB)
An allostratigraphic unit or allomember is a facies tract which is commonly not
bounded by time lines (isochrones). It often comprises different types of facies and its
isochrones may run obliquely through individual facies zones. In sequence stratigraphy, an allomember may describe a parasequence or a systems tract bounded by
diachronous erosional or transgressive surfaces
A Type I sequence boundary (SB!) is an erosional unconformity. It represents a stratigraphic gap (hiatus) of differing duration caused by subaerial and/or sub-marine erosion. This boundary is mostly diachronous and tends to become younger basinward
where it passes into a Type 2 sequence boundary (SB2). This boundary is a "correlative conformity"
System tracts are subunits of depositional sequences: lowstand systems tract LST,
transgressive systems tract TST, highstand systems tract HST, and shelf margin systems tract SMST
Systems tracts can be subdivided into smaller, commonly shallowing-upward units
called parasequences bounded by marine flooding surfaces (see below) which are assumed to be isochrones
Landward or basinward shifting of the coastline (and depocenter of sedimentation
(prograding and backstepping)
Diachronous surface indicating minor submarine erosion (no subaerial erosion) and
separating strata of shallower environment (bottom) from deposits of deeper environment (top). Correlative, less distinct surfaces m3Y exist on the coastal plain and the
shelf
This surface is the first significant marine flooding surface on top of the lowstand systems tract
This ± isochronous surface forms at the transition from TST to HST and reaches maximum landward extent. The toes of prograding HST clinoforms downlap onto this surface (downlap surface)
Thin unit of hemipelagic to pelagic marine sediments deposited in a relatively distal
basin position during the late TST and early HST
S tratal termination patterns in seismic stratigraphy (F ig. 7.3 f)
Eustasy, EU, signifies coeval global sea-Ievel
change which is controlled by two principal factors:
change in the volume of the ocean basins (tectonoeustasy) and/or change in the water volume of the
oceans (glacio-eustasy). The volume of the ocean
basins mainly results from the age and distribution of
continental and oceanic crust, i.e. plate tectonic proces ses. The ocean water volume changes with the