7.7 Continental Sequence Stratigraphy
347
Ci MAIN FACTORS CONTROLLING LAKE LEVELS
OPEN LAKES
ELEVATION OF
OUTFLOW
c--:::
~,* \;\='< ::?;~::~:J~:P>"""
EROSIONAL DOWNCUTTING
AND/OR TECTONISM
LAKE LEVEL
TIME (0. 1 - 1 Ma)
CLOSED LAKES, CLiMATE CONTROL
SPILL LEVEL OF BASIN (OPEN LAKE)
f
I
>100 m
I
TIME (10-'00 kaI .;
- _ .... _ .. ,
'--r--MORE HUMID
ARID
b RESPONSE OF LAKE SEDIMENTS TO Bl-CHANGE
± EVAPORITES
SHALE
(OPEN LACUSTRINE)
Fig. 7.30. a Principal types of lake-level changes of
open and closed lake basins. The upperrnost lake
level of closed basins is fixed by spill over which is
reached during relatively long periods of climatic
caused by northward drift of the Laurasian continent. This
change is reflected by the transition from red beds and
evaporites to playa mudstones and lacustrine carbonates. Finally, black shales were deposited in the basin center (Fig.
7.31). Along the basin margins deltaic and sandy foreshore
sediments dominated. Lake-level fluctuations, creating sequence boundaries and stratigraphie gaps, are well documented within this facies zone. During the late Triassie and
early Jurassie the c10sed basin experienced numerous highfrequency, fairly high-amplitude lake-level fluctuations with
TS
HIATUS
DELTA FRONT AND
DISTRIBUTARY CHANNEL
PRODELTA
AND SHOREFACE
cycles, whereas the level of the closed basin varies
frequently. (Partly based on Rogers and Astin 1991).
b Response of lake sediments and associated valleys
to lake-level changes. See text for further explanation
time periods in the range ofthe Milankovitch band. The lake
was ultimately flooded by the Jurassie (Pliensbachian) marine transgression.
An outstanding example of a continuous, annual c\imatic
record has been reported from varved Permian evaporites of
the Delaware Basin in New Mexico (Anderson 1982). The
measured sequence consists of calcite-laminated anhydrite
and anhydrite-laminated halite caused by seasonal changes in
temperature and evaporation (cf. Sect. 6.4.2). It represents a
time span of 260 ka, but can be subdivided into cyc\es of
347
Ci MAIN FACTORS CONTROLLING LAKE LEVELS
OPEN LAKES
ELEVATION OF
OUTFLOW
c--:::
~,* \;\='< ::?;~::~:J~:P>"""
EROSIONAL DOWNCUTTING
AND/OR TECTONISM
LAKE LEVEL
TIME (0. 1 - 1 Ma)
CLOSED LAKES, CLiMATE CONTROL
SPILL LEVEL OF BASIN (OPEN LAKE)
f
I
>100 m
I
TIME (10-'00 kaI .;
- _ .... _ .. ,
'--r--MORE HUMID
ARID
b RESPONSE OF LAKE SEDIMENTS TO Bl-CHANGE
± EVAPORITES
SHALE
(OPEN LACUSTRINE)
Fig. 7.30. a Principal types of lake-level changes of
open and closed lake basins. The upperrnost lake
level of closed basins is fixed by spill over which is
reached during relatively long periods of climatic
caused by northward drift of the Laurasian continent. This
change is reflected by the transition from red beds and
evaporites to playa mudstones and lacustrine carbonates. Finally, black shales were deposited in the basin center (Fig.
7.31). Along the basin margins deltaic and sandy foreshore
sediments dominated. Lake-level fluctuations, creating sequence boundaries and stratigraphie gaps, are well documented within this facies zone. During the late Triassie and
early Jurassie the c10sed basin experienced numerous highfrequency, fairly high-amplitude lake-level fluctuations with
TS
HIATUS
DELTA FRONT AND
DISTRIBUTARY CHANNEL
PRODELTA
AND SHOREFACE
cycles, whereas the level of the closed basin varies
frequently. (Partly based on Rogers and Astin 1991).
b Response of lake sediments and associated valleys
to lake-level changes. See text for further explanation
time periods in the range ofthe Milankovitch band. The lake
was ultimately flooded by the Jurassie (Pliensbachian) marine transgression.
An outstanding example of a continuous, annual c\imatic
record has been reported from varved Permian evaporites of
the Delaware Basin in New Mexico (Anderson 1982). The
measured sequence consists of calcite-laminated anhydrite
and anhydrite-laminated halite caused by seasonal changes in
temperature and evaporation (cf. Sect. 6.4.2). It represents a
time span of 260 ka, but can be subdivided into cyc\es of