7.9 Cyclo- and Event Stratigraphy
a
LACUSTRINE CYCLE
(NEWARK GROUP)
-1'CALCAREOUS CLAYSTONE
AND SILTSTONE,
I
ABUNDANT DESICCATION
I
CRACKS AND ROOT
I
:::rv:r-_ HORIZONS
I
---cryy (MUDFLAT !PLAYA FACIES)
I
---v-::rv=
I
I
BLACK SHALE.
CYCLE
CALCAREOUS.
MICROLAMINATED,
"'Sm
+FISH F:OSSILS. ETC.
I
(LACUSTRINE FACIES)
I
CALCAREOUS CLAYSTONE
I
OR SILTSTONE WITH
I
LENTICULAR LAMINATION,
I
BURROWS. MUDCRACKS
I
± OOLITES, STROMATOI
LlTES
I
~
(TRANSGRESSIVE
LAKE SHORE FACIES)
d AUTOCYCLIC
SEDIMENT
BUILDUP
SUBSIDENCE
FACIES
TIDAL
b
BACKREEF DACHSTEIN-TYPE
("LOFER CYCLE")
tI
DEEPENING
I
UPWARD
I
SUBTIDAL
f
I
I
BIOCLASTIC LlMESTONE, DIVERSE
CYCLE
MARINE FAUNA
"-'3.5m
MEGALODONTS
I
I
SUPRATIDAL -INTERTIDAL
I
ALGAL MATS ~OFERITES).
l _
±DOLOMITIC. UD CRACKS
EMERGENCE:
MICROKARST, SOlL
.. FORMATION
C
UNCONFORMITY
~ROOTS, SOlL , SHALLOWING
I
CALCRETE.
UPWARD
CYCLE
SABKHA
r
TlDAL CARBONATE,
LAGOONAL MUD
TRANSGRESSIVE
LAß
e ALLOCYCLIC
DEEP KARSTIWATER DEPTH
FICATION
EMERGENCE
AND LlMITED
EROSION
ISOCHRONES
(KARSTlFICATIONI
367
f
MEAN
SUPRATIDAL
SEA LEVEL
LlMESTON1
LOFER CYCLES
~DOLOMITE
~I~~~E
\ ~
TlDAL
I
~-- (END MEMBERS) --~ ~/
:-~
SUBTIDAL
... : ....
::~~~~~~~~~~:rw~:!::~!1!~~
Fig. 7.40. a Idealized sedimentary cyc1e in the lacustrine Triassic Newark Group, North America. b,c
Peritidal-lagoonal carbonate cycles from the Triassic
in the Alps (b) and southem Europe (c). The Lofer
cycles in Dachstein limestone display transgressive,
deepening-upward sequences tnmcated by emergence. cUpward shallowing Purbeckian cyc1es in the
Swiss-French Jura Mountains. (a,b Modified from
Fischer 1991; c after Haas 1991; Strasser 1991). d,e
Models to explain peritidal cyc1es by subsidence
alone (d autocyclic) or by sea level oscillations (e
allocyc1ic). (Based on Strasser 1991; Koerschner and
Read 1989). f Facies model for the generation of
symmetric and asymmetric peritidal carbonate cycles,
with or without dolomite. (After Haas 1991)