Geology Reference
In-Depth Information
the depositional interface is constantly above wave base.
Agitated-water sediments corresponding to Types III,
IV and V are more typical of the shallow water of shelf
areas, reef and bank settings as well as coastal regions.
on bedding planes). Paleocurrent analysis is primarily
an outcrop study, but some textural criteria can also be
studied in thin sections of oriented rock samples. Paleo-
current patterns of ancient shoreline grainstones based
on cross-bedding data were described by Knewtson and
Hubert (1969), and Stricklin and Smith (1973). The
orientation of clasts (Pl. 16/4, 7; Pl. 18/2; Pl. 139/8)
and fossils are useful criteria (Sect. 5.1.2).
Look for microphotographs showing the orientation
patterns of calcareous algae (Pl. 57/7, Pl. 58/1), fora-
minifera (Pl. 74/5, 8; Pl. 113/1), sponge spicules (Pl.
78/2; Pl. 112/1), mollusk shells (Pl. 18/1; Pl. 102/1, 6;
Pl. 113/2), and tentaculitids (Pl. 91/3, 4).
The differences between the more generalized
Plumley et al. classification and the more detailed En-
ergy Index Classification developed by Catalov (1972)
point to the necessity of revising the energy index con-
cept by considering those microfacies criteria that in-
dicate the degree of energy levels at the depositional
interface with reasonable safety. An attempt in this di-
rection was made by Bissell and Chilingar (1967), who
combined the Energy Index Classification with the
grain/micrite ratio
, proposed by Leighton and Pen-
dexter (1962) as well as with grain percentages. The
grain-micrite ratio is the sum of the percentages of all
grains divided by the percentage of micrite.
Basics: Hydrodynamic controls
Bollinger, W., Burri, P. (1970): Sedimentologie von Schelf-
Carbonaten und Beckenablagerungen im Oxfordian des
zentralen Schweizer Jura. Mit Beiträgen zur Stratigraphie
und Ökologie. - Beiträge zur Geologischen Karte der
Schweiz, Neue Folge,
140
, 1-96
Catalov, G.A. (1972): An attempt at energy index (EI) analy-
sis of the Upper Anisian, Ladinian and Carnian carbonate
rocks in the Teteven Anticlinorium (Bulgaria). - Sedimen-
tary Geology,
8
, 159-175
Grötsch, J., Koch, R., Buser, S. (1994): Fazies, Gildenstruktur
und Diagenese des nördlichen Randes der Dinarischen
Karbonatplattform (Barreme-Apt, W-Slowenien). - Ab-
handlungen der Geologischen Bundesanstalt Wien,
50
,
125-153
Hamblin, W.K. (1969): Marine paleocurrent directions in
limestones of the Kansas City Group (Upper Pennsylva-
nian) in Eastern Kansas. - Geological Survey of Kansas
Bulletin,
194
, 3-25
Skupin, K. (1973): Stratigraphy and microfacies in the
crinoidal limestones (Trochiten limestone, Triassic) of SW
Germany. - Sedimentary Geology,
9
, 1-19
Plumley, W.J., Risley, G.A., Graves, R.W., Kaley, M.E.
(1962): Energy index for limestone interpretation and clas-
sification. - In: Ham, W.E. (ed.): Classification of car-
bonate rocks. - Anerican Association of Petroleum Ge-
ologists, Memoir,
1
, 85-107
Potter, P.E., Pettijohn, F.J. (1977): Paleocurrents and basin
analysis. 2nd edition. - 425 pp., Berlin (Springer)
Riedl, R. (1969): Marinbiologische Aspekte der Wasser-
bewegung. - Marine Biology,
4
, 62-78
Stearn, C.W. (1982): The shapes of Paleozoic and modern
reef builders: a critical review. - Paleobiology,
8
, 228-241
Further reading:
K164, K165
Facies number:
Based on the system proposed by
Plumley et al. (1962), Grötsch (1993) introduced 'fa-
cies numbers' characterizing the degree of water en-
ergy and subdividing the mudstone to grainstone spec-
trum. Facies numbers are successfully used together
with compositional data in statistical analysis, e.g. of
cyclic carbonates (Grötsch et al. 1994).
12.1.1.3 Paleocurrent Data
Currents are major factors influencing the distribution
of sediment and of organisms. Global currents control
the distribution of larvae and of nutrients and water
temperature (scale: up to >1000 km). Currents control
the geometry of reefs (e.g. spur and groove structures),
influence the growth forms of reef builders (scale: about
10 to 1000 m, lateral; up to 100 m, vertical) and assist
in the transport of sand-grade sediment. Small-scale
currents are responsible for the transport of nutrients
and waste, and control the settlement of larvae (scale:
0.1-1.0 cm). Smallest scale currents are produced by
filtering organisms (scale: 0.1-10 cm). Both small-scale
and smallest-scale currents may also be common in low-
energy 'quiet-water' environments.
Paleocurrent indicators used in facies studies of car-
bonate rocks are essentially the same as those applied
to siliciclastic rocks (Potter and Pettijohn 1977; Miall
1990). Criteria allowing the existence and directions
of paleocurrents to be interpreted may indicate only
the sense of current flows (groove marks, channel struc-
tures, parting lineation) or both the sense and direction
of currents (cross-bedding, cross-lamination and ripple
marks, flute marks, slump folds; orientation of fossils
12.1.2 Storms
Storms leave distinct facies criteria in marine cold-
water carbonates (examples in James and Clarke 1997)
and warm-water carbonates as well as in coastal lake
sediments (e.g. Liu and Fearn 1993). The distribution
and taphonomic characters of fossils may be indicative
of storm events, because of a specific response of ani-
mals and plants to hurricanes (Walker et al. 1991).
