by sediment-laden swash. Typically, there is a shoreparallel zonation of both morphological forms and biological organisms, the zonation frequently being expressed
in different surface colors representing pigments of various microbial communities including cyanobacteria,
algae, and fungi that inhabit the beach rock. Diez et al.
(2007) show such communities can be dominated by
cyanobacteria that fix nitrogen at night, and constitute
important primary producers that provide the base of the
intertidal and nearshore food webs.
Bioerosional agents including fish, echinoderms,
worms, and mollusks feed on the microbial mats, and at
the same time, scrape, bore, and burrow into the beach
rock as do some of the blue-green algae (Algae, BlueGreen Boring). Many biolithophagic organisms produce
distinctive micromorphological features such as boreholes, burrows, and tunnels, while others leave smaller
traces like homing scars from limpets and tooth marks
from parrot fish. The geological significance of bioerosion
of beach rock was recognized several decades ago
(McLean, 1974) and the rates and impact of a number of
beach rock eroding taxa, including echinoderms and chitons continue to be investigated (e.g., Barbosa et al., 2008).
Kelletat (2006) has noted that many beach rocks are in
a state of destruction. Mechanical erosion and abrasion of
beach rock can result in smooth surfaces, as alluded to
above, and to the development of rhythmic transverse furrows or grooves in the lower tidal zone, and potholes in the
upper tidal zone. Other common features include undercuts, notches, fractures, and broken slabs caused by basal
undermining, marginal scour, and breakage due to mechanical strain and weakness. In places, where beach rock outcrops have been exposed for a long time, upper surfaces
often show a jagged pool and pinnacle topography or
microkarst resulting from a combination of solution processes (Solution Processes/Reef Erosion) and Bioerosion.
Destruction of beach rock can also be the result of
human activity, where outcrops are quarried like slates
and used as paving stones, building and fencing materials
and tombstones. Such usage is especially true on reef
islands in atoll states where solid rock is sparse.
Bibliography
Barbosa, S. S., Byrne, M., and Kelaher, B. P., 2008. Bioerosion
caused by foraging of the tropical chiton Acanthopleura
gemmata at One Tree Reef, southern Great Barrier Reef. Coral
Reefs, 27, 635–639.
Caldas, L. H. O., Stattegger, K., and Vital, H., 2006. Holocene sealevel history: evidence from coastal sediments of the northern
Rio Grande do Norte coast, NE Brazil. Marine Geology, 228,
39–53.
Chivas, A., Chappell, J., Polach, H., Pillans, B., and Flood, P., 1986.
Radiocarbon evidence for the timing and rate of island development, beach-rock formation and phosphatization at Lady Elliot
Island, Queensland, Australia. Marine Geology, 69, 273–287.
David, T. E. W., and Sweet, G., 1904. The geology of Funafuti. In
The Atoll of Funafuti: Borings into a Coral Reef and the Results.
London: Report of the Coral Reef Committee of the Royal Society, pp. 61–124.
Davies, P., and Kinsey, D.W., 1973. Organic and inorganic factors in
recent beach rock formation, Heron Island, Great Barrier Reef.
Journal of Sedimentary Petrology, 43, 59–81.
Diez, B., Bauer, K., and Bergman, B., 2007. Epilithic
cyanobacterial communities of a tropical beach rock (Heron
Island, Great Barrier Reef ): diversity and diazotrophy. Applied
and Environmental Microbiology, 73, 3656–3668.
Desruelles, S., Fouache, E., Ciner, A., Dalongeville, R.,
Pavlopoulos, K., Kosun, E., Coquinot, Y., and Potdevin, J. L.,
2009. Beachrocks and sea level changes since Middle Holocene:
comparison between the insular group of Mykonos-DelosRhenia (Cyclades, Greece) and the southern coast of Turkey.
Global and Planetary Change, 66, 19–33.
Gardiner, J. S., 1903. The Fauna and Geography of the Maldive and
Laccadive Archipelagoes. Cambridge: Cambridge University
Press, pp. 146–183, 313–346, 376–423.
Gischler, E., and Lomando, A. J., 1997. Holocene cemented beach
deposits in Belize. Sedimentary Geology, 110, 277–297.
Hopley, D., 1986. Beachrock as a sea-level indicator. In Van de
Plassche, O. (ed.), Sea-level Research: A Manual for the
Collection and Evaluation of Data. Norwich: Geo Books,
pp. 157–173.
Kelletat, D., 2006. Beachrock as sea-level indicator? Remarks from
a geomorphological point of view. Journal of Coastal Research,
22(6), 1558–1564.
Khadkikar, A. S., and Rajshekhar, C., 2003. Microbial cements in
Holocene beachrocks of South Andaman Islands, Bay of Bengal.
Current Science, 84, 933–936.
Knight, J., 2007. Beachrock reconsidered. Discussion of:
Kelletat, D. 2006. Beachrock as sea-level indicator? Remarks
from a geomorphological point of view. Journal of Coastal
Research, 23, 1074–1078.
Lambeck, K., Antonioli, F., Purcell, A., and Silenzi, S., 2004. Sealevel change along the Italian coast for the past 10,000 yr. Quaternary Science Reviews, 23, 1567–1598.
McLean, R. F., 1974. Geologic significance of bioerosion of
beachrock. Proceedings Second International Coral Reef Symposium, 2, 401–408.
Scoffin, T. P., and Stoddart, D. R., 1983. Beachrock and intertidal
cements. In Goudie, A. S., and Pye, K. (eds.), Chemical Sediments
and Geomorphology: Precipitates and Residua in the NearSurface Environment. London: Academic, pp. 401–425.
Stoddart, D. R., and Cann, J. R., 1965. Nature and origin of
beachrock. Journal of Sedimentary Petrology, 35, 243–273.
Tatumi, S. H., Kowata, E. A., Gozzi, G., Kassab, L. R., Suguio, K.,
Barreto, A. M., and Bezerra, F. H., 2003. Optical dating
results of beachrock, eolic dunes and sediments applied to
sea-level changes study. Journal of Luminescence, 102–103,
562–565.
Vousdoukas, M. I., Velegrakis, A. F., and Plotmaritis, T. A., 2007.
Beachrock occurrence, characteristics, formation mechanisms
and impacts. Earth Science Reviews, 85, 23–46.
Cross-references
Algae, Blue-Green Boring
Aragonite
Bioerosion
Calcite
Conglomerates
Eolianite
Micrite
Phosphatic Cay Sandstone
BEACH ROCK
111
in different surface colors representing pigments of various microbial communities including cyanobacteria,
algae, and fungi that inhabit the beach rock. Diez et al.
(2007) show such communities can be dominated by
cyanobacteria that fix nitrogen at night, and constitute
important primary producers that provide the base of the
intertidal and nearshore food webs.
Bioerosional agents including fish, echinoderms,
worms, and mollusks feed on the microbial mats, and at
the same time, scrape, bore, and burrow into the beach
rock as do some of the blue-green algae (Algae, BlueGreen Boring). Many biolithophagic organisms produce
distinctive micromorphological features such as boreholes, burrows, and tunnels, while others leave smaller
traces like homing scars from limpets and tooth marks
from parrot fish. The geological significance of bioerosion
of beach rock was recognized several decades ago
(McLean, 1974) and the rates and impact of a number of
beach rock eroding taxa, including echinoderms and chitons continue to be investigated (e.g., Barbosa et al., 2008).
Kelletat (2006) has noted that many beach rocks are in
a state of destruction. Mechanical erosion and abrasion of
beach rock can result in smooth surfaces, as alluded to
above, and to the development of rhythmic transverse furrows or grooves in the lower tidal zone, and potholes in the
upper tidal zone. Other common features include undercuts, notches, fractures, and broken slabs caused by basal
undermining, marginal scour, and breakage due to mechanical strain and weakness. In places, where beach rock outcrops have been exposed for a long time, upper surfaces
often show a jagged pool and pinnacle topography or
microkarst resulting from a combination of solution processes (Solution Processes/Reef Erosion) and Bioerosion.
Destruction of beach rock can also be the result of
human activity, where outcrops are quarried like slates
and used as paving stones, building and fencing materials
and tombstones. Such usage is especially true on reef
islands in atoll states where solid rock is sparse.
Bibliography
Barbosa, S. S., Byrne, M., and Kelaher, B. P., 2008. Bioerosion
caused by foraging of the tropical chiton Acanthopleura
gemmata at One Tree Reef, southern Great Barrier Reef. Coral
Reefs, 27, 635–639.
Caldas, L. H. O., Stattegger, K., and Vital, H., 2006. Holocene sealevel history: evidence from coastal sediments of the northern
Rio Grande do Norte coast, NE Brazil. Marine Geology, 228,
39–53.
Chivas, A., Chappell, J., Polach, H., Pillans, B., and Flood, P., 1986.
Radiocarbon evidence for the timing and rate of island development, beach-rock formation and phosphatization at Lady Elliot
Island, Queensland, Australia. Marine Geology, 69, 273–287.
David, T. E. W., and Sweet, G., 1904. The geology of Funafuti. In
The Atoll of Funafuti: Borings into a Coral Reef and the Results.
London: Report of the Coral Reef Committee of the Royal Society, pp. 61–124.
Davies, P., and Kinsey, D.W., 1973. Organic and inorganic factors in
recent beach rock formation, Heron Island, Great Barrier Reef.
Journal of Sedimentary Petrology, 43, 59–81.
Diez, B., Bauer, K., and Bergman, B., 2007. Epilithic
cyanobacterial communities of a tropical beach rock (Heron
Island, Great Barrier Reef ): diversity and diazotrophy. Applied
and Environmental Microbiology, 73, 3656–3668.
Desruelles, S., Fouache, E., Ciner, A., Dalongeville, R.,
Pavlopoulos, K., Kosun, E., Coquinot, Y., and Potdevin, J. L.,
2009. Beachrocks and sea level changes since Middle Holocene:
comparison between the insular group of Mykonos-DelosRhenia (Cyclades, Greece) and the southern coast of Turkey.
Global and Planetary Change, 66, 19–33.
Gardiner, J. S., 1903. The Fauna and Geography of the Maldive and
Laccadive Archipelagoes. Cambridge: Cambridge University
Press, pp. 146–183, 313–346, 376–423.
Gischler, E., and Lomando, A. J., 1997. Holocene cemented beach
deposits in Belize. Sedimentary Geology, 110, 277–297.
Hopley, D., 1986. Beachrock as a sea-level indicator. In Van de
Plassche, O. (ed.), Sea-level Research: A Manual for the
Collection and Evaluation of Data. Norwich: Geo Books,
pp. 157–173.
Kelletat, D., 2006. Beachrock as sea-level indicator? Remarks from
a geomorphological point of view. Journal of Coastal Research,
22(6), 1558–1564.
Khadkikar, A. S., and Rajshekhar, C., 2003. Microbial cements in
Holocene beachrocks of South Andaman Islands, Bay of Bengal.
Current Science, 84, 933–936.
Knight, J., 2007. Beachrock reconsidered. Discussion of:
Kelletat, D. 2006. Beachrock as sea-level indicator? Remarks
from a geomorphological point of view. Journal of Coastal
Research, 23, 1074–1078.
Lambeck, K., Antonioli, F., Purcell, A., and Silenzi, S., 2004. Sealevel change along the Italian coast for the past 10,000 yr. Quaternary Science Reviews, 23, 1567–1598.
McLean, R. F., 1974. Geologic significance of bioerosion of
beachrock. Proceedings Second International Coral Reef Symposium, 2, 401–408.
Scoffin, T. P., and Stoddart, D. R., 1983. Beachrock and intertidal
cements. In Goudie, A. S., and Pye, K. (eds.), Chemical Sediments
and Geomorphology: Precipitates and Residua in the NearSurface Environment. London: Academic, pp. 401–425.
Stoddart, D. R., and Cann, J. R., 1965. Nature and origin of
beachrock. Journal of Sedimentary Petrology, 35, 243–273.
Tatumi, S. H., Kowata, E. A., Gozzi, G., Kassab, L. R., Suguio, K.,
Barreto, A. M., and Bezerra, F. H., 2003. Optical dating
results of beachrock, eolic dunes and sediments applied to
sea-level changes study. Journal of Luminescence, 102–103,
562–565.
Vousdoukas, M. I., Velegrakis, A. F., and Plotmaritis, T. A., 2007.
Beachrock occurrence, characteristics, formation mechanisms
and impacts. Earth Science Reviews, 85, 23–46.
Cross-references
Algae, Blue-Green Boring
Aragonite
Bioerosion
Calcite
Conglomerates
Eolianite
Micrite
Phosphatic Cay Sandstone
BEACH ROCK
111