Geology Reference
In-Depth Information
Fig. 21.20
Panorama of conspicuously bedded peritidal
carbonate successions along the Azadshahr Highway in eastern
Alborz Mountains: (
a
) Highstand lagoonal shallowing-upward
cycles of the Upper Permian Ruteh Formation (
right
) capped by
a laterite horizon, which is in turn overlain by the peritidal cycles
of the Lower Triassic lower member of the Elika Formation.
(
b
) The Lower and Middle Triassic peritidal deposits of the
lower and middle members of the Elika Formation comprising
two depositional sequences. The lower sequence is bounded by
the lowstand laterite horizon at the Permian-Triassic boundary
(
right
) and a quartz sandstone bed at the Lower-Middle Triassic
boundary in the middle of the photograph, and consists of
lagoonal- to intertidal cycles intercalated by numerous storm
beds. The Middle Triassic middle member (
upper left
of the
photograph) is a depositional sequence composed almost entirely
of intertidal- to supratidal shallowing-upward cycles
21.6.1.3 Sequence Stratigraphy
The meter-scale cycles are superimposed on an under-
lying lower-frequency 3rd-order relative sea level
cycle (e.g. Goldhammer et al.
1993
; Kerans and Tinker
1997
; Spence and Tucker
2007
) (see the Middle
Triassic tidalites in Sect.
21.7.5.2
for an example). The
3rd-order cycle has a duration of 1-3 my (Haq et al.
1987
) or 1-10 my, (Kerans and Tinker
1997
; Lehrmann
with subaerial exposure surface or karstic/calichie soil
cap, and asymmetric deepening-upward can develop
depending on tectonic setting. The cycles have the
same thickness and frequency as eustatic or autocyclic
processes, however, lateral variation of cycle types and
cycle stacking and irregular non-bundled stacking of
the cycles support an overriding tectonic control
(De Benedictis et al.
2007
; Bosence et al.
2009
) .
