Geology Reference
In-Depth Information
1 cm
Fig. 20.2.
Thin section of a recent warm-temperate carbonate sediment deposited on a volcanic seamount (Gettysburg
Seamount, Atlantic Ocean, W of Gibraltar, 86 m water depth). This highly diverse sample contains fragments of herbivorous
gastropods, bryozoans (mainly cheilostome bryozoans), sessile benthonic foraminifera (
Miniacina miniacea
), serpulids,
bivalves, echinoids, coralline algae, and volcanic rocks. The coralline alga indicates that at least part of sediment was formed
within the photic zone.
BI - Bivalves, BR - Bryozoans, CA - Coralline red algae, ECH - Echinoid spine, FOR - Foraminifera (
Miniacina
), GA -
Gastropods, SERP - Serpulids, SI - Siliciclastic debris
1 cm
Fig. 20.3.
Thin section of a recent beach deposit near Tromsø (N-Norway), rich in fragments of coralline algae (
Lithothamnium
glaciale
), balanid plates, bivalves, gastropods, echinoderms (sea urchins), serpulids, bryozoans, and siliciclastic rock fragments.
Beach deposits very often represent a mixture of different littoral environments. High abundance of organisms needing a
hard substrate for their metamorphosis and growth (balanids, coralline algae) is typical for rocky shores as e.g. in northern
Norway.
BI - Bivalves, BA - Balanids, BR - Bryozoans, CA Coralline red algae (upper corner: bored), ECH - Echinoid spines, GA -
Gastropods, SI - Siliciclastic grains
