provided for non-commercial research and educational use only. …€¦ · this chapter was...

Provided for non-commercial research and educational use only. Not for reproduction, distribution or commercial use.

This chapter was originally published in the Treatise on Geomorphology, the copy attached is provided by Elsevier for the author’s benefit and for the benefit of the author’s institution, for non-commercial research and educational use.

This includes without limitation use in instruction at your institution, distribution to specific colleagues, and providing a copy to your institution’s administrator.

All other uses, reproduction and distribution, including without limitation commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution’s website or repository, are prohibited.

For exceptions, permission may be sought for such use through Elsevier’s permissions site at:

http://www.elsevier.com/locate/permissionusematerial

De Waele J., and Furlani S. (2013) Seawater and Biokarst Effects on Coastal Limestones. In: John F. Shroder (ed.) Treatise on Geomorphology, Volume 6, pp. 341-350. San Diego: Academic Press.

© 2013 Elsevier Inc. All rights reserved.

Author's personal copy

6.28 Seawater and Biokarst Effects on Coastal LimestonesJ De Waele and S Furlani, Dipartimento di Scienze della Terra e Geologico-Ambientali, Bologna, Italy, and Dipartimento diGeoscienze, Trieste, Italy

r 2013 Elsevier Inc. All rights reserved.

6.28.1 Introduction 341
6.28.2 Historical Perspective 341 6.28.3 Coastal Karst 343 6.28.4 Seawater Effects 344 6.28.5 Biokarst Effects 344 6.28.6 Resulting Morphologies 347 6.28.7 Conclusions 348 References 348
De

lim

Ge

Ge

Tre

GlossaryEndolith Organism that lives inside rock or other hard

materials, or in the pores between mineral grains of a rock.

An euendolith penetrates actively into the interior of rocks;

a chasmoendolith colonizes fissures and cracks in the rock,

whereas a cryptoendolith colonizes structural cavities

within porous rocks, including spaces produced and

vacated by euendoliths

Eogenetic Associated with the depositional environment

of the carbonate rock. Eogenetic forms occur in young

limestones that are still undergoing consolidation and early

diagenesis.

Epilith Organism (e.g., plant and fungus) that lives on the

rock surface.

Flank margin cave A natural cave formed at the

freshwater–seawater mixing zone in generally young

(eogenetic) limestone close to the coast.

Waele, J., Furlani, S., 2013. Seawater and biokarst effects on coastal

estones. In: Shroder, J. (Editor in Chief), Frumkin, A. (Ed.), Treatise on

omorphology. Academic Press, San Diego, CA, vol. 6, Karst

omorphology, pp. 341–350.

atise on Geomorphology, Volume 6 http://dx.doi.org/10.1016/B978-0-12-3747

Micro-erosion meter (and traversing micro-erosion

meter) Instrument that consists of a dial gauge

(micrometer) which measures the height of rock

surface with relation to a fixed reference

position.

Phytokarst Coastal carbonate rock deeply pitted by

biologically enhanced dissolution, commonly darkly

colored because of the presence of boring algae and

other organisms.

Solution pan A relatively shallow, subcircular, generally

flat-bottomed basin formed by commonly biologically

enhanced dissolution upon an exposed carbonate surface;

also known as kamenitze.

Trottoir A constructional bench formed by

calcareous algae (e.g., Lithophyllum) at the mid-tide

level.

Abstract

Coastal limestones are characterized by a typical set of morphologies throughout the world, related to a combination of

physical, chemical, and biological processes, the relative importance of each depends on geographical and local conditions.In tropical and temperate areas biological processes are dominant, whereas at high latitudes physical abrasion becomes

more important. The morphology of limestone coasts depends on a wide set of interrelated processes that are locally

contingent and, therefore, cannot be described by a global scheme.

6.28.1 Introduction

In storm-wave environments at high latitudes, mechanical

wave action plays a dominant role over bioerosion and bio-

corrosion in the shaping of coasts, biological and chemical

processes are predominant on coastal karst at mid- and low

latitudes. The related coastal landscape is, therefore, charac-

terized by morphologies that are mainly originated by chem-

ical and biological marine weathering, such as notches, karren,

tidal pools, and ‘black phytokarst’. They develop mainly in the

intertidal zone, where these processes are focused (Trudgill,

1985). Even if the debate on the relative contribution of the

different processes on coastal limestones is far from being

solved (Spencer, 1988), they do produce well-defined ero-

sional features. Sometimes the form and distribution of

coastal landforms are closely related to past sea levels and they

can be considered as inherited karst morphologies.

The analysis of seawater and biokarst effects on coastal

limestones involves karstologists, geomicrobiologists, geo-

morphologists, biologists, and geologists. This causes the

overlap of terms used by different fields of work and the no-

menclature is consequently characterized by different words

indicating similar morphologies and/or processes.

39-6.00109-3 341

342 Seawater and Biokarst Effects on Coastal Limestones


6.28.2 Historical Perspective

Although some interesting observations on coastal limestones

have been carried out since the beginning of the nineteenth

century, detailed studies started in the 1950s. Stephenson and

Stephenson (1949) suggested that the zonation of organisms

is a characteristic feature of rocky shores, distinguishing

a supratidal, intertidal, and subtidal zone. Their position

and the boundaries between them depend on the bedrock,

on the slope (Chapman and Trevarthen, 1953; Lewis, 1964)

and on the climatic setting (Schneider, 1976). Guilcher

(1953), in the first detailed work on limestone coast geo-

morphology (Figure 1), suggested the term ‘corrosion’ as the

sum of chemical and biological processes acting on coastal

carbonates.

Neumann (1966) introduced the term bioerosion, study-

ing the bioerosive effects of living sponges in the intertidal

zone. Fairbridge (1968) pointed out that ‘‘much more needs

to be known about the actual mechanisms by which organ-

isms destroy rocky substrates and about the zonation of

rocky-destroying organisms and the relationship between

these communities and the morphologic features of the coast’’.

Trudgill (1985) studied coastal erosion processes and focused

attention on rates and forms. Also, Trenhaile (1987) broadly

described the morphologies associated with coastal carbonates

and the relative processes. Detailed studies on the biological

activity on the bedrock have been carried out, for example,

marine borers (Becker, 1959; Bathurst, 1966) or, more in

general the bioerosion of rocky coasts (Bromley, 1978), or

about the interrelationships between biotic and abiotic factors

British Isles

Solution pits

Pools

Pools andkarren

Tenareatrottoir

High tideLow tide

Karren

Mediterranean (Provence)

Figure 1 Littoral limestone zonations.

(Trudgill, 1976). Studies of the biological communities and

their role in the substrate corrosion have focused attention on

etching (Viles, 1987; Jones, 1989; Pohl and Schneider, 2002),

on the mechanical processes (Moses and Smith, 1993), and

on grazing (Trudgill, 1987; Andrews and Williams, 2000); the

term ‘bioerosion’ was preferred (Torunski, 1979).

Trudgill (1985) gave an overview on coastal limestones, the

processes and their relative importance. Since the 1970s, a

number of authors tried to quantify limestone erosion by

using direct field methods, such as the microerosion meter

(MEM; High and Hanna, 1970) and the traversing microero-

sion meter (TMEM; Trudgill et al., 1981), or laser scanner

techniques (Swantesson et al., 2006). Also the contribution of

biological processes affecting the platform morphologies and

downwearing (Naylor and Viles, 2002; Fornos et al., 2006),

the short-time surface variations of coastal limestones, both

on natural (Gomez-Pujol et al., 2007) and laboratory-made

surfaces (Furlani et al., 2010), and the role of different

lithologies and textural manipulations in influencing early-

stage biotic colonization have also been investigated.

Interest in rocky coasts has increased over the last decade

(Robinson and Lageat, 2006). Some interesting reviews

on shore platforms and rocky coasts (Stephenson, 2000;

Trenhaile, 2002), as reported by Stephenson and Brander

(2003), and a recent special issue on rock coast geomorph-

ology (Stephenson and Naylor, 2010) witness the increasing

interest on this theme. Coastal weathering has also been in-

vestigated using mathematical models (e.g. Trenhaile, 2001),

in order to study the relationships at different timescales be-

tween processes and geomorphology.

Morocco (Atlantic)

Pools

Karren

Tropics (Oahu, Hawai’i)

NotchPools

Limestone

Deepened pools

Pools andkarren

Seawater and Biokarst Effects on Coastal Limestones 343


6.28.3 Coastal Karst

The coastal karst represents the contact between soluble car-

bonate rocks and seawater. Karst coasts show characteristic

small- and medium-scale landforms not present elsewhere

and related to their lithologic nature and the wide range of

processes contributing to the destruction and construction of

carbonate rocks (Trudgill, 1985). Geomorphic processes can

be subdivided into chemical, physical, and biological types,

with the biological characteristically being the most powerful

in shaping intertidal carbonate coastlines. Processes include

wave action (wave and storm-wave quarrying), haloclastism,

wetting and drying, splash and spray impact, mixing cor-

rosion, dissolution, and biological action, as bioconstruction

and accretion, bioerosion and biocorrosion (Figure 2). Their

relative importance mainly depends on the mineralogical

composition of the limestones, the geographic and climatic

setting, and the position with respect to the mean sea level and

its evolution in the past.

Mechanical wave attack is an important erosional agent on

many limestone coasts, not only in storm environments,

playing an important role in joint block removal (Naylor

and Stephenson, 2010). In general, high wave energy and

the presence of sediments increase abrasion and generally

decrease biological colonization.

Chemical and salt weathering, as wetting and drying, salt

crystallization, and other processes, are very active in warm

climates, especially in the intertidal zone, whereas splash and

spray erosion–corrosion is also active in the supratidal zone.

Physical abrasion is obviously more important in the lower

intertidal and subtidal zones.

Dissolution of carbonates in seawater, although very

slow, can be induced by many mechanisms such as increase

in carbon dioxide by respiring organisms or decay of organic

matter, chelation with organic compounds, and differential

dissolution of carbonate minerals. Slightly undersaturated

conditions are normally reached in calm, isolated, or

inshore waters during the night, when carbon dioxide is

released into the water and mixing is less important. Also,

seawater–freshwater mixing is known to enhance dissolution

Spitzkarren

Intertidalnotch

Bio

corr

osio

n

Bio

cons

truc

tion

Dis

solu

tion

Mix

ing

corr

osio

n

Wet

ting/

dryi

ng

Hal

ocla

stis

m

Bio

eros

ion

Accretions

Sheltered

Moderately

exposed

Figure 2 General scheme of the vertical zonation of geomorphic processecoast at middle and low latitudes.

of carbonates. Mixing corrosion can become important in

tropical high rainfall areas or simply in carbonate coastlines

where freshwater springs or rivers bring large quantities of

freshwater to the sea.

The subdivision in supratidal, intertidal, and subtidal

zones is generally not sufficient to adequately describe car-

bonate coasts. Besides tidal levels, the effects of direct wave

attack, wave splash and spray, insolation and temperature

variations, nearshore fluctuations in seawater chemistry, and

rainfall should also be considered. Moreover, the changing

zone boundaries that result from the interaction of these

factors (Figure 3) are further modified by substrate type

(Chapman and Trevarthen, 1953) and shore platform gradient

(Lewis, 1964).

Morphological zonation on karst coasts commonly broadly

corresponds to biological zonation and reflects tidal levels and

a wide set of environmental parameters (Lewis, 1964; Lund-

berg, 2004). A biological subdivision of carbonate coasts is

commonly used for tropical and midlatitude coasts (Schneider,

1976; Taylor, 1978). In particular, Schneider (1976) proposed a

general scheme of evolution based essentially on moisture re-

tention, and thus biological colonization (bioerosion).

Morphology of coasts also greatly depends on exposure

to winds, waves, and storms and on tidal range. In sheltered

areas, a tidal notch will form, whereas exposed coasts typically

have tidal platforms mostly made of carbonate-encrusting

organisms. In these high-energy environments, bioerosion

with formation of a notch can continue in the subtidal zone.

In microtidal environments, notches will be deep and con-

centrated on a small vertical range, whereas in higher-energy

environments they become higher and less deeply carved.

Other important factors that influence the morphology of

carbonate coasts are lithology and structure. Well-cemented,

metamorphized, and recrystallized older carbonate rocks are

more resistant to both erosion and corrosion than are eoge-

netic Tertiary and Quaternary limestones. Also, bedding

planes and fractures are controlling factors, favoring dis-

solution, increasing the surface on which colonization can

take place, and creating favorable environmental conditions

for biota.

Spl

ash

Spr

ay

Abr

asio

n

Wav

e qu

arry

ing

Sto

rm w

ave

quar

ryin

g

Tidal pools

High tide

Low tide

Subtidal notch

Very exposed

s on a sheltered, moderately exposed, and very exposed limestone

SpitzkarrenHigh tide

Low tide

Tidal pool

Biocorrosion

Bioerosion

Bioconstruction

Dissolution

Mixing corrosion

Wetting/drying

Haloclastism

Splash

Spray

Abrasion

Wave quarrying

Storm wave quarrying

Subtidalnotch

Figure 3 General scheme of the horizontal zonation of geomorphicprocesses on a limestone coast at middle and low latitudes.Thickness of gray horizontal bars is indicative of the importance ofthe process.



From the above discussion, it is clear that there is no

global scheme that explains the morphology of carbonate

coasts. Many factors and processes contribute to their for-

mation, and although several general schemes can be defined,

generally local conditions (exposure, lithology, biological

colonization, climate, etc.) are the most determinant ones. For

example, geomorphological landforms on a limestone coast

can change drastically even at the scale of some hundreds of

meters.

Coastal karst has been extensively studied in the tropics, such

as at Aldabra atoll (Indian Ocean) (Trudgill, 1976, 1979; Viles

et al., 2000), the Cayman Islands (Folk et al., 1973; Jones, 1989),

the Mariana islands (Taborosi et al., 2004; Jenson et al., 2006),

and the Bahamas (Mylroie et al., 1995). Most of these areas are

characterized by eogenetic limestones of Tertiary and Quaternary

age (Vacher and Mylroie, 2002). Similar calcareous arenites have

been studied in subtropical Morocco (Duane et al., 2003), SE

Australia (Moses, 2003), and Mediterranean areas (De Waele

et al., 2009). In this last area, diagenetic limestones of Tertiary

and Mesozoic age, instead, have been studied in Mallorca

(Gomez-Pujol et al., 2006) and the Adriatic coast (Schneider,

1976; Torunski, 1979). Nice case studies on coastal karst areas in

cool and temperate areas have been carried out on Carbonifer-

ous massive crystalline limestones in Ireland (Trudgill, 1987)

and in the Bristol channel (Ley, 1979). More to the north, in

cold temperate climates, an interesting study on marine karren

developed in Precambrian marbles has been published by

Holbye (1989).

Rates and effects of biological and solutional processes can

be quantitatively measured through in situ measurements of

surface changes (Stephenson and Finlayson, 2009), through

experimentation with exposure blocks, the collection of sedi-

ment products or laser scanner techniques (Swantesson et al.,

2006). The MEM (High and Hanna, 1970) and the TMEM

(Trudgill et al., 1981) methods are probably the most used

all over the world for measuring limestone lowering rates

(Torunski, 1979; Cucchi and Forti, 1989; Gomez-Pujol et al.,

2007; Furlani et al., 2009; Stephenson and Finlayson, 2009).

Rates of bioerosion have been summarized by Trudgill (1985),

Trenhaile (1987), and Spencer (1988). MEM, TMEM, and

laser scanner measurements are reported in Table 1.

6.28.4 Seawater Effects

The word corrosion was introduced by Guilcher (1953) in this

context and includes different chemical, physicochemical,

and biological processes operating on carbonate-rich rocks in

coastal environments and resulting in specific erosional

features.

The effectiveness of seawater to dissolve calcium carbonate

is still debated. The coastal seawater, in fact, is saturated or

oversaturated with calcium carbonate, but data indicate that

the emission of carbon dioxide by green algae living in pools

can dissolve carbonates, in particular during the night. Trudgill

suggested that in tropical environments undersaturation of

inshore waters may occur at night with respect to calcite and at

any time with respect to aragonite and high magnesian calcite,

accounting for some 10% of the erosion in coralline limestones

(Trudgill, 1976). Besides, many authors identified coastal

morphologies clearly formed by dissolutional processes. Hig-

gins (1980), studying tidal notches in Greece, observed these

developed better in correspondence with submarine springs

suggesting a link between freshwater and notch carving. The

rate of sea corrosion in carbonate rocks has been measured in a

great number of sites all over the world (see Table 1). A mean

rate of about 1 mm yr�1 may be considered as an average.

Dissolution is particularly important in the marine and

freshwater mixing zone, where the introduction of foreign

ions into a saturated CaCO3 solution increases solubility of

carbonate minerals. Some morphological expressions of this

mixing zone are the above-mentioned tidal notch (Higgins,

1980), enlarged cave entrances and flank margin caves

(Mylroie and Carew, 1990) (Figure 4).

These caves are typically formed along the border of the

freshwater lens where it comes into contact with the marine

water (respectively, at the base and at the top of the lens).

Mixing phenomena are also responsible for the develop-

ment of the microcanyons in the intertidal zone described

in calcareous arenites along the Somalian coast (Forti and

Francavilla, 1990).

6.28.5 Biokarst Effects

Bioerosion, a term for the removal of rock by the direct action

of living organisms, is generally acknowledged to play an

important role in the development of coastal corrosional

Figure 4 The karst estuary of St. Paul’s Underground River (Palawan, Philippines). Tidal effects and seawater–freshwater mixing are veryimportant in the shaping of this extensive karst system. Photos Paolo Petrignani, La Venta Exploring Team.

Table 1 Limestone lowering rates collected using MEM, TMEM, and laser scanner

Authors Location Mean annual rates (mm yr�1)

Cucchi and Forti (1989) Coastal classical karst (Italy) 0.009–0.194 (coastal karst morphologies)Spencer (1985) Grand Cayman Islands 0.29–3.67 (subtidal), 0.31–3.01 (intertidal), 0.09–1.77 (surf platform)Kirk (1977) Kaikoura Peninsula 1.53 (shore platform)Stephenson and Kirk (1996) Kaikoura Peninsula 1.10 (limestone platforms)Stephenson (1998) Kaikoura Peninsula 0.875 (limestone platforms)Torunski (1979) Gulf of Piran, Slovenija 0.07–1.114 (intertidal limestones)Trudgill et al. (1976) Aldabra Atoll, Indian Ocean 2.0–4.0Trudgill et al. (1981) Country Clare (Ireland) 0.145–0.383Viles and Trudgill (1984) Aldabra Atoll, Indian Ocean 1.27 (Ramp edge), 2.20 (Ramp foot)Neves et al. (2001) Portugal 0.153 (Intertidal limestone)Furlani et al. (2009) Northeastern Adriatic coast 0.08–2.966 (intertidal limestones)Furlani et al. (2010) Northeastern Adriatic coast (intertidal limestone manmade slab)Swantesson et al. (2006) Mallorca 0.090 (coastal limestone)

Source: Adapted from Stephenson, W.J., Finlayson, B.L., 2009. Measuring erosion with the micro-erosion meter – Contributions to understanding landform evolution. Earth-Science

Reviews 95, 53–62; Furlani, S., Cucchi, F., Forti, F., Rossi, A., 2009. Comparison between coastal and inland Karst limestone lowering rates in the northeastern Adriatic Region (Italy

and Croatia). Geomorphology 104, 73–81, and Furlani, S., Cucchi, F., Odorico, R., 2010. A new method to study microtopographical changes in the intertidal zone: one year of

TMEM measurements on a limestone removable rock slab (RRS). Zeitschrift fur Geomorphologie N.F. 54, 137–151.



features, not only in the tropics where an enormously varied

marine biota lives on calcareous substrates, but also at higher

latitudes (Kelletat, 1988). Organisms involved in the coastal

erosion can act both directly, by rasping away the rock surfaces

during grazing and boring activity, and indirectly influencing

local chemical environment (Trudgill, 1985). Biologists and

geologists have described a number of bioeroding organisms:

algae, bacteria, foraminifera, sponges, bryozoa, annelid

worms, barnacles, gastropods, bivalves, echinoderms, fish, and

mammals (Fox, 2005).

Organisms constitute an important erosive factor, both

creating specific morphologies and increasing the total



denudation rates on preexistent landforms (Spencer, 1988).

On the contrary, some organisms may form encrustations and,

therefore, protect the substrate from denudation processes

(bioprotection) (Naylor and Viles, 2002).

Bioerosional activity is mainly the result of the combin-

ation of physical and chemical processes. Torunski (1979)

distinguished between biological abrasion that produces de-

tritus and biological corrosion, solutional processes produced

by microorganisms without supply of erosion products.

Bioerosion is affected by: (1) environmental, (2) physical/

chemical, (3) lithological factors, and (4) ecological (biotic)

interactions. Environmental factors include the distribution of

marine organisms, both in the vertical and horizontal plane

(Doty, 1957), the tidal and wave environment, and the

availability of moisture. Physical/chemical factors include the

variability of parameters such as salinity, temperature, pH,

sunlight exposure, etc, whereas lithological factors include

both the nature of the substrate and its structure (porosity,

bedding, joints and fractures) (Naylor and Stephenson, 2010).

Organisms on coasts can be classified by size (micro- or

macrounits) and niche type. Although epiliths live on the

rock surface, endoliths live embedded within the substrate

(Golubic et al., 1981). Endoliths are divided in euendoliths

(a)

(c)

Figure 5 Some examples of biokarst effects on coastal limestones: (a) boF Antonioli); (b) circular holes excavated by Patella cerulea (Sussex, Englanbarnacles (Balanus) covering (Adriatic sea, Croatia), which produce wide pr

that actively bore the bedrock, chasmoendoliths that inhabit

existing fractures, and cryptoendoliths that live in the porous

substrates (Ginsburg, 1953).

Algae are probably the most important erosive organisms,

both in the intertidal and the supralittoral zones (Nadson,

1927; Ginsburg, 1953; Dalongeville, 1977). Endolithic algae

penetrate the bedrock and are connected to the surface by a

network of filaments (Trenhaile, 1987). Conversely, epilithic

algae can potentially protect the rock surface, but can be

limited in occurrence by the presence of grazing organisms in

the intertidal and eulittoral zone.

Surface lowering, however, results also from grazing activ-

ity of macroorganisms, following the foraging and feeding

behavior of the interested species. Grazers, such as the gas-

tropods Littorina and Patella (Figure 5(b)), can cause mech-

anical rasping of rock surfaces, that have been previously

weakened by the penetration of endolithic algae, following

interlinked processes (Spencer, 1988). Limestone destruction

can be produced by mechanical weathering, such as the action

produced by the chiton Acanthopleura that erodes the rock

using its radula teeth.

Borers are responsible for excavations into the substrate.

The upper intertidal and supratidal zones are characterized by

(b)

(d)

reholes drilled by Lithophaga litophaga (Tyrrhenian Sea, Italy) (photod); (c) cyanobacteria on coastal limestones (Istria, Croatia); (d)otective crusts.



epilithic and endolithic microorganisms, the latter pitting the

surface rather than shaping true boreholes. The subtidal zone

is dominated by cyanobacteria that penetrate the surface up to

a depth of 600–900 mm (Figure 5(c)). Schneider (1976) dis-

tinguished true endoliths, or perforants, from cariants, epiliths

that corrode the surface giving a fretted or carious aspect.

Fungi and sponges bore deeper than algae and they are not

dependant upon light. Limestone holes can be produced also

by bivalve barnacles and other molluscs, which produce tub-

ular borings up to several centimeters (Figures 5(a) and 5(d)).

The most important is Lithophaga and the barnacle Lithotrya

(Ansell and Nair, 1969; Carriker and Smith, 1969). They act

through mechanical boring facilitated by acid secretion, which

causes the softening of the rock.

Even the sponges pertaining to the genus Cliona, which

are able to bore microscopic to macroscopic excavations in

limestones, play a particularly important role in the disinte-

gration of rock substrates. Also worms, such as Polydora, may

be active borers in calcareous substrates. Biological erosion is

of great significance on limestone coasts, justifying the use of

the term of biokarst proposed for the resulting forms (Spencer,

1988).

6.28.6 Resulting Morphologies

Small- and mid-scale seawater solution and bioerosion

morphologies (from millimeters to meters) are easily recog-

nized along the limestone coasts, whereas at a greater scale the

corrosion effects, in particular biological effects (Spencer,

1988), are more difficult to confirm. Coastal karst morphol-

ogies occur on different types of coast: shore platforms,

plunging cliffs, and limestone ramp coast, each of them

showing a distinct combination of forms.

Coastal karren are distinctive meso- and microlandforms

of the littoral karst areas, differing substantially from their

inland cousins from a genetic point of view; whereas moun-

tainous karren assemblages are mainly formed by dis-

solutional processes, with only subordinate importance of

biological and physical ones, marine karren are the product of

a combination of dissolutional, physical, and biological pro-

cesses, with the biological largely prevailing. The coastal kar-

ren assemblages can be distinguished commonly by form

and processes in zones parallel to the coast, and these gener-

ally take the names of the prevailing organisms living therein

(e.g., Verrucaria, Littorina, Barnacle, and Mussel) (Lundberg,

2004).

The most characteristic karst forms are the solution pans,

whose genesis is related to a combination of salt, biological,

and dissolution weathering. They resemble the kamenitze of

mountain karsts, especially in the supratidal zone, and look

like basins with flat floors (Trenhaile, 1987). Some authors

refer to them as tidal pools, although this term should be

restricted to solution pans in the intertidal zone. The rock

surfaces in between these basins are pitted by circular milli-

meter-sized holes, called alveoli. In this location, their origin

is due to differential salt weathering combined with biological

and dissolution processes (Moses, 2003).

Tidal pools are shallow, flat-bottomed depressions

frequently occurring on limestone coasts. These coastal

features are prominent structures that form in the intertidal

zone where resistant bedrock is exposed (Griggs, 2007)

(Figure 6(c)). Tidal pools develop from small pits or holes, a

few centimeters in size, and over time they reach several

meters of diameter. Their genesis is related to the type of rock

exposed, the tidal range, the wave action, the erosion, and the

weathering processes acting on the rocks (De Waele et al.,

2009).

In many tropical coasts, the differential dissolution of

eogenetic limestones leads to the formation of a very jagged

black-coated pinnacle karst (spitzkarren) (Figure 6(d)), for

which the term phytokarst is generally used (Folk et al., 1973;

Bull and Laverty, 1982; Jones, 1989). Although it is better to

use the term biokarst, implying both plant- and animal-

induced karst, the role of cyanobacteria, algae, and lichens is

commonly by far dominant in sculpturing the carbonate rock.

Where these karren forms are displayed on young immature

limestones the term eogenetic karren is preferred (Vacher and

Mylroie, 2002). Light-oriented (or -directed) phytokarst has

been reported as photokarren in literature (Bull and Laverty,

1982), not only for tropical areas but also in Mediterranean

settings (De Waele et al., 2009) and in temperate cold coastal

areas (Simms, 1990).

In exposed coastal karst areas in cold climates, dissolu-

tional and physical processes (abrasion) dominate over bio-

logical ones, thereby creating a particular set of coastal karren.

These circular depressions, called bowl-karren, appear to form

due to turbulent dissolution on inclined carbonate outcrops

(Holbye, 1989; Lundberg and Lauritzen, 2002).

Limestone rocks are commonly eroded into the shape of a

notch, mainly on vertical rock surfaces (Figure 6(a)). Notches

are horizontal erosion features extended along the intertidal

zone of marine cliffs. They are characterized by horizontal

back-wearing of rocky shore faces, most commonly along

extensive and continuous stretches of the coastline. Their

relation to tidal levels and their shape may differ from

place to place. Two main genetic types of notches can be

distinguished around the coastlines of the world: surf

notches, cut above high tide level in exposed sites, and tidal

notches, well developed in relatively protected sites (Pirazzoli,

1986). Tidal notches cut on stacks may result in mushroom-

like morphologies (Paskoff, 2005) (Figure 6(a)). Double

notches occur both in the tropics (Focke, 1978), whose

genesis is related to high wave exposure, and in the Medi-

terranean, where Antonioli et al. (2006) suggested that their

genesis is related to a glacial isostatic adjustment of the

coastline.

Among the biokarst effects, bioconstruction plays an im-

portant role in shaping the limestone coasts. Trottoirs and

corniches are organic protrusions that grow out from steep

rock surfaces at about the sea level or, alternatively, rock ledges

with a thin crust of organic material (Peres, 1968), generally,

but not exclusively, occurring on carbonate rocks of the

Mediterranean and tropical seas (Guilcher, 1953; Laborel and

Laborel-Deguen, 1996).

Corniches are mainly composed of the calcareous alga

Tenarea tortuosa and other Melobesiacieae algae (Lithophyllum

incrustans, Lithopthamnium lenormandi, etc.). The accumu-

lations, absent in sheltered areas, protrude 0.5–2 m in length

at around mean sea level (Guilcher, 1953).

(a) (b)

(c) (d)

Figure 6 Coastal morphologies on littoral limestones: (a) tidal notch (Barbados); (b) trottoirs along the coast of San Vito Lo Capo with thecharacteristic ‘plate-a vasques’ (Sicily, Italy); (c) tidal pools (Malta); (d) pinnacles on Miocene limestones (Punta Funtanas, Sardinia).



Trottoirs are generally associated with thin crusts of Den-

dropoma petraeum below mean tide in the infralittoral zone,

well developed at the seaward margin of the platform, as

in Algeria and Sicily, corresponding to the most agitated

water. This produces ‘plate-forme a vasques’, that is shallow

pools separated by elevated Vermetid ridges (Molinier, 1955)

(Figure 6(b)). Trottoirs are common also in tropical areas.

6.28.7 Conclusions

As previously suggested, there is no global theory able to

summarize the complexities of coastal karst geomorphology.

One of the most important tasks of the scholars who study

carbonate coasts is to provide clear explanations of the origin

and development of coastal karst corrosional and erosional

features. This study passes necessarily through any detailed

definition of the processes acting and requires a multi-

disciplinary approach. The direct measurement of coastal

erosion rates with continuously improving instruments and

the emplacement of continuous monitoring stations will

provide robust databases allowing recording of slight but

significant surface changes. Remote-sensing techniques, such

as terrestrial laser scanning enables monitoring of coastal

sites in a much easier and precise way. At the microscale,

different microscopic techniques (optical microscopy, scan-

ning electron microscope, scanning laser microscopy), re-

cently applied to study rock surfaces, are promising.

References

Andrews, C., Williams, R.B.G., 2000. Limpet erosion of chalk shore platforms insoutheast England. Earth Surface Processes and Landforms 25, 1371–1381.

Ansell, A.D., Nair, N.B., 1969. A comparative study of bivalves which bore mainlyby mechanical means. American Zoologist 9, 857–868.

Antonioli, F., Ferranti, L., Kershaw, S., 2006. A glacial isostatic adjustment originfor double MIS 5.5 and Holocene marine notches in the coastline of Italy.Quaternary International 145–146, 19–29.

Bathurst, R.G.C., 1966. Boring algae, micrite envelopes, and lithification ofmolluscan biosparites. Geological Journal 5, 15–32.

Becker, G., 1959. Biological investigations on marine borers in Berlin-Dahlem.In: Ray, D.L. (Ed.), Marine Boring and Fouling Organisms. University ofWashington Press, Seattle, pp. 62–83.

Bromley, R.G., 1978. Bioerosion of Bermuda reefs. PalaeogeographyPalaeoclimatology Palaeoecology 23, 169–197.

Bull, P.A., Laverty, M., 1982. Observations on phytokarst. Zeitschrift furGeomorphologie N.F. 26, 437–457.

Carriker, H.R., Smith, E.H., 1969. Comparative calcibiocavitology: summary andconclusions. American Zoologist 9, 1011–1020.

Chapman, V.J., Trevarthen, C.B., 1953. General schemes of classification in relationto marine coastal zonation. Journal of Ecology 41, 198–204.



Cucchi, F., Forti, P., 1989. Misure in situ di corrosione di rocce carbonatiche.XV Congresso Nazionale di Speleologia, pp. 623–634.

Dalongeville, M., 1977. Formes littorales de corrosion dans les roches carbonateesau Liban. Mediterranee 30, 21–33.

De Waele, J., Mucedda, M., Montanaro, L., 2009. Morphology and origin of coastalkarst landforms in Miocene and Quaternary carbonate rocks along the central-western coast of Sardinia (Italy). Geomorphology 106, 26–34. http://dx.doi.org/10.1016/J.Geomorph.2008.09.017.

Doty, M.S., 1957. Rock intertidal surfaces. In: Hedgpeth, J. (Ed.), Treatise onMarine Ecology and Paleoecology. Memoirs of the Geological Society ofAmerica. Boulder, Colorado, vol. 67, pp. 535–585.

Duane, M.J., Al-Mishwat, A.T., Rafique, M., 2003. Weathering and biokarstdevelopment on marine terraces, northwest Morocco. Earth Surface Processesand Landforms 28, 1439–1449. http://dx.doi.org/10.1002/Esp.1002.

Fairbridge, R.W., 1968. The Encyclopedia of Geomorphology. Encyclopedia of EarthSciences Series, 3. Reinhold Book Corporation, New York.

Focke, J.W., 1978. Limestone cliff morphology on Curac-ao (Netherlands Antilles),with special attention to the origin of notches and vermetid/coralline algal surfbenches (‘‘cornices’’, ‘‘trottoirs’’). Zeitschrift fur Geomorphologie N.F. 22,329–349.

Folk, R.L., Roberts, H.H., Moore, C.H., 1973. Black phytokarst from Hell,Cayman Islands, British West Indies. Geological Society of America Bulletin 84,2351–2360.

Fornos, J.J., Pons, G.X., Gomez-Pujol, L., Balaguer, P., 2006. The role of biologicalprocesses and rates of downwearing due to grazing organisms on Mallorcancarbonate coasts (western Mediterranean). Zeitschrift fur Geomorphologie N.F.supplementband 44, 161–181.

Forti, P., Francavilla, F., 1990. The hydrogeology of some coastal paleodunes in anequatorial area and their karst related morphologies: the case of Gesira(Somalia). Proceedings of the International Symposium on HydrologicalProcesses in Karst Terranes. Antalya, Turkey, pp. 133–138.

Fox, W.T., 2005. Bioerosion. In: Schwartz, M.L. (Ed.), Encyclopedia of CoastalScience, pp. 191–192.

Furlani, S., Cucchi, F., Forti, F., Rossi, A., 2009. Comparison between coastaland inland Karst limestone lowering rates in the northeastern Adriatic Region(Italy and Croatia). Geomorphology 104, 73–81. http://dx.doi.org/10.1016/J.Geomorph.2008.05.015.

Furlani, S., Cucchi, F., Odorico, R., 2010. A new method to studymicrotopographical changes in the intertidal zone: one year of TMEMmeasurements on a limestone removable rock slab (RRS). Zeitschrift furGeomorphologie N.F. 54, 137–151.

Ginsburg, R.N., 1953. Intertidal erosion on the Florida Keys. Bulletin of MarineScience 3, 55–69.

Golubic, S., Friedmann, I., Schneider, J., 1981. The lithobiontic ecological nichewith special reference to microorganisms. Journal of Sedimentary Petrology 51,475–479.

Gomez-Pujol, L., Fornos, J.J., Swantesson, J.O.H., 2006. Rock surface millimetre-scale roughness and weathering of supratidal Mallorcan carbonate coasts(Balearic Islands). Earth Surface Processes and Landforms 31, 1792–1801. http://dx.doi.org/10.1002/Esp.1379.

Gomez-Pujol, L., Stephenson, W.J., Fornos, J.J., 2007. Two-hourly surface changeon supra-tidal rock (Marengo, Victoria, Australia). Earth Surface Processes andLandforms 32, 1–12. http://dx.doi.org/10.1002/Esp.1373.

Griggs, G., 2007. Tidepools, formation and rock types. In: Denny, M.W., Gaines,S.D. (Eds.), Encyclopedia of Tidepools and Rocky Shores, pp. 586–588.

Guilcher, A., 1953. Essai sur la zonation et la distribution des formes littorals dedissolution du calcaire. Annales de Geographie 62, 161–179.

Higgins, C.G., 1980. Nips, notches, and the solution of coastal limestone: anoverview of the problem with examples from Greece. Estuarine and CoastalMarine Science 10, 15–30.

High, C.J., Hanna, F.K., 1970. Method for the direct measurements of erosion onrock surfaces. Britisch Geomorphological Research Group Technical Bulletin 5,1–25.

Holbye, U., 1989. Bowl-karren in the littoral karst of Nord-Arnoy, Norway. CaveScience 16, 19–26.

Jenson, J.W., Keel, T.M., Mylroie, J.R., Mylroie, J.E., Stafford, K.W., Taborosi, D.,Wexel, C., 2006. Karst of the Mariana Islands: the interaction of tectonics,glacio-eustasy, and freshwater/seawater mixing in island carbonates.Perspectives on Karst Geomorphology, Hydrology, and Geochemistry 404,129–138.

Jones, B., 1989. The role of microorganisms in phytokarst development ondolostones and limestones, Grand Cayman, British West Indies. CanadianJournal of Earth Sciences 26, 2204–2213.

Kelletat, D., 1988. Quantitative investigations on coastal bioerosion in highertidal latitudes: an example from northern Scotland. Geooekodynamik 9,41–51.

Laborel, J., Laborel-Deguen, F., 1996. Biological indicators of Holocene sea-leveland climatic variations on rocky coasts of tropical and subtropical regions.Quaternary International 31, 53–60.

Lewis, J.R., 1964. The Ecology of Rocky Shores. English University Press, London.Ley, R.G., 1979. The development of marine karren along the Bristol Channel

coastline. Zeitschrift fur Geomorphologie N.F. 32, 75–89.Lundberg, J., 2004. Coastal Karst. In: Gunn, J. (Ed.), Encyclopedia of Caves and

Karst Science. Routledge, London, pp. 231–233.Lundberg, J., Lauritzen, S.-E., 2002. The search for an arctic coastal karren model

in Norway and Spitzbergen. In: Hewitt, K., Byrne, M.-L., English, M., Young, G.(Eds.), Landscapes of Transition. Kluwer Acamedic Publisher, Amsterdam, pp.185–203.

Molinier, R., 1955. Les plate-formes et corniches recifales de vermets (VermetusCristatus Biondi) en Mediterranee occidentale. Comptes Rendus de l’Academiedes Sciences 240, 361–363.

Moses, C.A., 2003. Observations on coastal biokarst, Hells Gate, Lord Howe Island,Australia. Zeitschrift fur Geomorphologie 47, 83–100.

Moses, C.A., Smith, B.J., 1993. A note on the role of the lichen Collema-Auriformain solution basin development on a Carboniferous limestone substrate. EarthSurface Processes and Landforms 18, 363–368.

Mylroie, J.E., Carew, J.L., 1990. The flank margin model for dissolution cavedevelopment in carbonate platforms. Earth Surface Processes and Landforms 15,413–424.

Mylroie, J.E., Carew, J.L., Vacher, H.L., 1995. Karst development in the Bahamasand Bermuda. In: Curran, H.A., White, B. (Eds.), Geological Society of AmericaSpecial Paper. Boulder, Colorado, pp. 251–267.

Nadson, G., 1927. Les algues perforantes, leur distribution, et leur role dansla nature. Comptes rendus de l’Academie des Sciences Serie 184, 896–898.

Naylor, L.A., Stephenson, W.J., 2010. On the role of discontinuities in mediatingshore platform erosion. Geomorphology 114, 89–100. http://dx.doi.org/10.1016/J.Geomorph.2008.12.024.

Naylor, L.A., Viles, H.A., 2002. A new technique for evaluating short-term ratesof coastal bioerosion and bioprotection. Geomorphology 47, 31–44. PiiS0169-555x(02)000139-3.

Neumann, A.C., 1966. Observations on coastal erosion in Bermuda andmeasurements of the boring rate of the sponge Cliona lampa. Limnology andOceanography 11, 92–108.

Paskoff, R.P., 2005. Karst coasts. In: Schwartz, M.L. (Ed.), Encyclopedia of CoastalScience. Springer, Dordrecht, pp. 581–586.

Peres, J.M., 1968. Trottoir. In: Fairbridge, R.W. (Ed.), Encyclopedia ofGeomorphology, pp. 1173–1174.

Pirazzoli, P.A., 1986. Marine notches. In: Van de Plassche, O. (Ed.), Sea-LevelResearch: A Manual for the Collection and Evaluation of Data. Geo Books,Norwich, pp. 361–400.

Pohl, W., Schneider, J., 2002. Impact of endolithic biofilms on carbonaterock surfaces. Geological Society of London, Special Publication 205,177–194.

Robinson, D.A., Lageat, Y., 2006. European Shore Platform Dynamics. Zeitschrift furGeomorphologie Supplementband, 144. Borntraeger, Stuttgart.

Schneider, J., 1976. Biological and inorganic factors in the destruction of limestonecoasts. Contributions in Sedimentology 6, 112.

Simms, M.J., 1990. Phytokarst and photokarren in Ireland. Cave Science 17,131–133.

Spencer, T., 1988. Limestone coastal morphology: the biological contribution.Progress in Physical Geography 12, 66–101.

Stephenson, T.A., Stephenson, A., 1949. The universal features between tide markson rocky coasts. Journal of Ecology 37, 289–305.

Stephenson, W.J., 2000. Shore platforms: a neglected coastal feature? Progress inPhysical Geography 24, 311–327.

Stephenson, W.J., Brander, R.W., 2003. Coastal geomorphology into the twenty-firstcentury. Progress in Physical Geography 27, 607–623.

Stephenson, W.J., Finlayson, B.L., 2009. Measuring erosion with the micro-erosionmeter-Contributions to understanding landform evolution. Earth-Science Reviews95, 53–62. http://dx.doi.org/10.1016/J.Earscirev.2009.03.006.

Stephenson, W.J., Naylor, L., 2010. Rock coast geomorphology. Geomorphology114, 1–2.

Swantesson, J.O.H., Moses, C.A., Berg, G.E., Jansson, K.M., 2006. Methods formeasuring shore platform micro erosion: A comparison of the micro-erosionmeter and laser scanner. Zeitschrift fur Geomorphologie N.F. Supplementband44, 1–17.



Taborosi, D., Jenson, J.W., Mylroie, J.E., 2004. Karren features in IslandKarst: Guam, Mariana Islands. Zeitschrift fur Geomorphologie 48,369–389.

Taylor, J.D., 1978. Zonation of rocky intertidal surfaces. In: Stoddart, D.R.,Johannes, R.E. (Eds.), Coral Reefs: Research Methods. Monographs onOceanographic Methodology. UNESCO, Paris, pp. 139–148.

Torunski, H., 1979. Biological erosion and its significance for the morphogenesis oflimestone coasts and for nearshore sedimentation (northern Adriatic).Senckenbergiana Maritima 11, 193–265.

Trenhaile, A.S., 1987. The Geomorphology of Rock Coasts. Clarendon Press,Oxford.

Trenhaile, A.S., 2001. Modeling the effect of late Quaternary interglacial sea levelson wavecut shore platforms. Marine Geology 172, 205–223.

Trenhaile, A.S., 2002. Rock coasts, with particular emphasis on shore platforms.Geomorphology 48, 7–22.

Trudgill, S., High, C.J., Hanna, K.K., 1981. Improvements to the micro-erosion meter(MEM). British Geomorphological Research Group Technical Bulletin 29, 3–17.

Trudgill, S.T., 1976. The marine erosion of limestones on Aldabra Atoll. IndianOcean. Zeitschrift fur Geomorphologie N.F. 26, 164–200.

Trudgill, S.T., 1979. Spitzkarren on calcarenites, Aldabra Atoll, Indian Ocean.Zeitschrift fur Geomorphologie N.F. 32, 67–74.

Trudgill, S.T., 1985. Limestone Geomorphology. Geomorphology texts, 8. LongmanGroup Ltd., London.

Trudgill, S.T., 1987. Bioerosion of intertidal limestone, Co. Clare, Eire – 3:zonation, process and form. Marine Geology 74, 111–121.

Vacher, H.L., Mylroie, J.E., 2002. Eogenetic karst from the perspective of anequivalent porous medium. Carbonates and Evaporites 17, 182–196.

Viles, H.A., 1987. Blue-green algae and terrestrial limestone weathering on Aldabraatoll: an S.E.M. and light microscope study. Earth Surface Processes andLandforms 12, 319–330.

Viles, H.A., Spencer, T., Teleki, K., Cox, C., 2000. Observations on 16 years ofmicrofloral recolonization data from limestone surfaces, Aldabra Atoll, Indianocean: implications for biological weathering. Earth Surface Processes andLandforms 25, 1355–1370.

Biographical Sketch

Dr. Jo De Waele (born in Deinze, 1968) is a graduate of the University of Ghent (Belgium). He did his PhD in

mineral prospection at the Department of Engineering Geology and Environmental Techniques (DIGITA) of the

University of Cagliari (Italy). He is currently an associate professor at the Department of Earth Sciences and

Environmental Geology of the University of Bologna Alma Mater (Italy). His main interests include environ-

mental geology, physical geography, geomorphology, hydrogeology, and paleoclimate studies in karst areas. The

results of his researches have been published in more than 120 scientific papers since 1993. Jo is editor-in-chief

(from 2005) of the International Journal of Speleology and has guest-edited special issues for Engineering

Geology (Elsevier), Environmental Geology (Springer), Geomorphology (Elsevier), Zeitschrift fur Geomorpho-

logie (Borntraeger, Germania), and Geodinamica Acta (Lavoisier).

Dr. Stefano Furlani (born in Trieste, 1973) is a graduate of the University of Trieste (Italy). He did his PhD in

geomatics and GIS at the Department of Geological, Environmental and Marine Sciences, (DISGAM) of the

University of Trieste (Italy). He is currently an assistant researcher at the Department of Geography ’G. Morandini’

of the University of Padova (Italy) and he collaborates with the Department of Geosciences of the University of

Trieste (regarding karst studies). His main interests include environmental geology, physical geography, geo-

morphology of coasts and deserts, and sea-level change studies, mainly in Mediterranean areas. He projects and

develops field instruments to evaluate rock surface lowering and rock erosion rates. The results of his researches

have been published in more than 70 scientific papers since 1999.

provided for non-commercial research and educational use only. …€¦ · this chapter was...

Documents