Sandstone Boulders Research Articles

A new species of Uperoleia (Anura: Myobatrachidae) from the northwest Kimberley, Western Australia

Uperoleia is a large genus of small-bodied terrestrial frogs that occur in Australia and southern New Guinea. With nine species, the Kimberley region in northern Western Australia is the most diverse. Recent surveys of the northwest coast of the Kimberley have revealed a tenth species of Uperoleia. The new species is characterized by a combination of small body size, dark and slightly tubercular dorsal skin, basal webbing between the toes, outer metatarsal tubercle spatulate and oriented perpendicular to the foot, possession of maxillary teeth, a broadly exposed frontoparietal fontanelle and the advertisement call is a high-pitched rasp. All specimens collected have been associated with sandstone boulders or escarpments with flowing water or rock pools. The northwest Kimberley is an isolated region of high rainfall and rugged terrain that possesses high biodiversity for many plant and animal groups and is therefore worthy of special conservation attention.

Surface exposure ages imply multiple low-amplitude Pleistocene variations in East Antarctic Ice Sheet, Ricker Hills, Victoria Land

AbstractOne of the major issues in (palaeo-) climatology is the response of Antarctic ice sheets to global climate changes. Antarctic ice volume has varied in the past but the extent and timing of these fluctuations are not well known. In this study, we address the question of amplitude and timing of past Antarctic ice level changes by surface exposure dating using in situ produced cosmogenic nuclides (10Be and 21Ne). The study area lies in the Ricker Hills, a nunatak at the boundary of the East Antarctic Ice Sheet in southern Victoria Land. By determining exposure ages of erratic boulders from glacial drifts we directly date East Antarctic Ice Sheet variations. Erosion-corrected neon and beryllium exposure ages indicate that a major ice advance reaching elevations of about 500 m above present ice levels occurred between 1.125 and 1.375 million years before present. Subsequent ice fluctuations were of lesser extent but timing is difficult as all erratic boulders from related deposits show complex exposure histories. Sample-specific erosion rates were on the order of 20–45 cm Ma-1 for a quartzite and 10–65 cm Ma-1 for a sandstone boulder and imply that the modern cold, arid climate has persisted since at least the early Pleistocene.

Age and significance of former low-altitude corrie glaciers on Hoy, Orkney Islands

Synopsis Geomorphological mapping provides evidence for two former low-level corrie glaciers on Hoy, both defined by end moraines. Five 10 Be exposure ages obtained from sandstone boulders on moraine crests fall within the range 12.4 ± 1.5 ka to 10.4 ± 1.7 ka (weighted mean 11.7 ± 0.6 ka), confirming that these glaciers developed during the Loch Lomond (Younger Dryas) Stade (LLS) of 12.9–11.5 cal. ka bp , and demonstrate the feasibility of using this approach to establish the age of LLS glacier limits. The equilibrium line altitude (ELA) of one of the glaciers (99 m) is the lowest recorded for any LLS glacier, and the area-weighted mean ELA for both (141 m) is consistent with a general northward ELA decrease along the west coast of Britain. The size of moraines fronting these small (≤0.75 km 2 ) glaciers implies that glacier termini remained at or close to their limits for a prolonged period. The apparent restriction of LLS glaciers to only two sites on Hoy probably reflects topographic favourability, and particularly the extent of snow-contributing areas.

Characterization of mortars used for the construction of Saithidai Heroon Podium (1st century AD) in ancient Messene, Peloponnesus, Greece

The Saithidai Heroon Podium is a Mausoleum dated to the Roman Period located in ancient Messene, Peloponnesus, Greece. Its outer walls were constructed with porous and massive limestone blocks with no mortar in the joints. The core of the podium was filled by rock chips to angular boulders of sandstone, limestone, sand, gravel and earthy groundmass material. The groundmass is mostly composed of quartz and calcite, with minor amounts of clay minerals. Small, irregular lime lumps also occur, composed of authigenic euhedral calcite crystal assemblages and rare sub-microscopic quartz fragments, or rod-like CaO/SiO 2-rich mineral assemblages developed in pore spaces on fine-grained authigenic calcite crystals. The mortar used for the filling material of the Podium was poorly homogenized semi-hydraulic lime derived from the calcination of pure limestone and siliceous limestone fragments, possibly the waste material from the finishing of the building blocks of the Podium walls.

Comparisons between the influences of habitat, body size and season on the dietary composition of the sparid Acanthopagrus latus in a large marine embayment

Seasonal samples from Shark Bay on the west coast of Australia were used to determine (1) the habitats occupied by the juveniles and adults of Acanthopagrus latus in this large subtropical marine embayment and (2) the extent to which the dietary composition of this sparid is influenced by habitat type, body length and season. Sampling was undertaken in two habitat types in which A. latus was known to be abundant, namely mangrove ( Avicennia marina) creeks and nearby rocky areas, the latter comprising sandstone boulders and/or limestone reefs. The mean total length ±95% CLs of A. latus was far lower in mangrove creeks, 126 ± 6.1 mm, than in rocky areas, 313 ± 4.7 mm. As A. latus attains maturity at ca. 245 mm, the juveniles of this species typically occupy mangrove areas and then, with increasing body size, move to nearshore rocky areas, where they become adults. The species composition of the food ingested by juvenile A. latus in mangrove creeks differed markedly from that of large juveniles and adults in rocky areas. Based on analyses of data for both habitat types combined, this difference was far greater than that between size classes and season, which was negligible. There were indications, however, that, overall within each habitat, the dietary composition did change seasonally, although not with body size. Acanthopagrus latus fed predominantly on mangrove material, sesarmid crabs and small gastropods in mangrove habitats, and mainly on Brachidontes ustulatus in rocky areas, where this mytilid bivalve is very abundant. The mangrove material, which contributed nearly 40% of its overall dietary volume in mangrove creeks, consisted mainly of lateral root primordia. This apparently unique food source for a teleost is presumably ingested through subsurface nipping, which would be facilitated by the mouth and dentitional characteristics of sparids. The almost total lack of correspondence in the dietary compositions of fish in the length class that was well represented in both mangrove and rocky areas illustrates the extent to which this sparid is capable of opportunistic feeding behaviour.

Siliciclastic slope deposits from the Cretaceous Abeokuta Group, Dahomey (Benin) Basin, southwestern Nigeria

Outcrops in the Cretaceous Abeokuta Group of the Dahomey (Benin) Basin in southwestern Nigeria are described. Based on detailed sedimentological logging, 13 lithofacies were delineated. They are: massive and loose sand; cross-bedded loose sand; normally graded sandstone (upward fining sandstone); laminated silt; clay; laminated sandstone; clay with sandstone injections and clasts (sandstone boulders); clayey sand with sandstone boulders; silty clay with intraformational folds and breccias; highly contorted conglomerate/clayey silt; and channel infills. The association of the lithofacies and their sedimentary structures support that these lithologies were deposited by turbidity current, grain flow, debris flow, liquefied flow and fluidized flow. Since these depositional features are diagnostic of slope environments, the Cretaceous Abeokuta Group was concluded to have been deposited in slope environments.

Tortella bambergeri (Schimp.) Broth. in the British Isles

The moss Tortella bambergeri (Schimp.) Broth. is added to the described British bryophyte flora. It differs from fragile-leaved forms of T. tortuosa (Hedw.) Limpr. in having the apical quarter of the costa with quadrate, papillose abaxial cells and in having the peristome teeth twisted by a half turn instead of one and a half turns. Other identification features are discussed, and the habitat and distribution of T. bambergeri in Britain are described. Most records are from sandstone boulders in western Britain.

Didymodon bistratosus (Pottiaceae) in the New World

New to the Americas from California isDidymodon bistratosus J.-P. Hebrard & R. B. Pierrot, differing significantly from congeners by the deep red lower portions of the plant, and 2-3-stratose upper lamina. In California it was found on a sandstone boulder in a mesic oak woodland. Its range worldwide is restricted to California, the Iberian Peninsula and Turkey.

A novel Antarctic microbial endolithic community within gypsum crusts.

A novel endolithic microbial habitat is described from a climatically extreme site at Two Step Cliffs, Alexander Island, Antarctic Peninsula (71 degrees 54'S, 68 degrees 13'W). Small endolithic colonies (<3 mm in diameter) are found within the translucent gypsum crust that forms on the surface of sandstone boulders. Gypsum crusts are found on ice-free rocks throughout the Antarctic and therefore offer potential colonization sites at more inhospitable locations, including sites at higher latitudes. Cyanobacterial, bacterial and fungal components were cultured from the crust material and have been identified as Chloroglea sp., Sphingomonas sp. and Verticillium sp. respectively. A non-cultured, black-pigmented fungus was also found. Cyanobacterial primary productivity is low: at depths of 1.2 and 2.5 mm within the crust, estimates of possible cell divisions per year were < 38 and four respectively. This microniche is proposed to provide protection from desiccation, rapid temperature variation and UV radiation flux while allowing penetration of photosynthetically active radiation (PAR) for utilization by phototrophs. The endolithic communities are less extensive than those of the Dry Valleys, continental Antarctica, probably owing to only recent deglaciation (<7000 year ago).

Boulder weathering and erosion associated with a wildfire, Sierra Ancha Mountains, Arizona

An April–May 2000 “Coon Creek Fire” burned ∼37.5 km 2 of the Sierra Ancha Mountains, 32.3 km miles north of Globe, AZ—including 25 sandstone and 19 diorite boulders surveyed in 1989 and resurveyed after the burn, after the summer 2000 monsoon season, and after the winter 2001 season. When viewed from the perspective of cumulative eroded area, both sandstone and diorite displayed bimodal patterns with 79% of sandstone boulder area and 93% of diorite boulder area undergoing either no fire-induced erosion or fire-induced erosion >76 mm. When stretched over cumulative boulder areas, erosion due to the fire averaged >26 mm for sandstone and >42 mm for diorite. Post-fire erosion from thunderstorm summer rains averaged <1 mm for 5 diorite and 1 mm for 10 sandstone boulders. While only a single diorite boulder eroded an average of 1.2 mm after the winter, winter erosion removed an average of 5.5 mm from 14 sandstone boulders. Thus, fire appears to increase a rock's susceptibility to post-fire weathering and erosion processes, as predicted by Goudie et al. [Earth Surf. Process. Landf. 17 (1992) 605]. In contrast to experimental research indicating the importance of size in fire weathering, no statistically significant relationship exists between erosion and boulder height or boulder surface area—a result similar to Zimmerman et al. [Quat. Res. 42 (1994) 255]. These data exclude 12 original sites and 85 boulders at sites impacted by the fire that could not be relocated, with a reasonable cause for the lack of relocation being boulder obliteration by the fire. Given evidence from 10Be and 26Al cosmogenic nuclides [Earth Planet. Sci. Lett. 186 (2001) 269] supporting the importance of boulders in controlling evolution of nonglaciated, bouldered landscapes [Geol. Soc. Amer. Bull. 76 (1965) 1165], fire obliteration of boulders could be an important process driving drainage evolution in nonglaciated mountains.

Testing for reach-scale adjustments of hydraulic variables to soluble and insoluble strata: Buckeye Creek and Greenbrier River, West Virginia

An open question exists as to whether channel geometries and hydraulics are adjusted in bedrock streams with stable, concave profiles in a manner analogous to alluvial rivers. As a test of this problem, a comparison was undertaken of channel geometries and hydraulics among reaches with substrates that are of high mechanical resistance, but of variable chemical resistance. Reaches were selected from Buckeye Creek and Greenbrier River, West Virginia, USA because these streams flow over sandstones, limestones, and shales. The limestones have Selby rock resistance scores similar to those of the sandstones. A total of 13 reaches consisting of between 6 and 26 cross sections were surveyed in the streams. HEC-RAS was used to estimate unit stream power ( ω) and shear stress ( τ) for each reach. The reaches were selected to evaluate the null hypothesis that that ω and τ are equal atop soluble versus insoluble bedrock. Hypothesis tests consisted of paired t-tests and simultaneous, multiple comparisons. Geomorphic setting was included for Greenbrier River because previous studies have suggested that bedrock streams are intimately coupled with hillslopes. Holding geomorphic setting constant, three separate comparisons of ω and τ reveal that these variables are lowest atop soluble substrates in Greenbrier River (significance ≤0.05) and that changes in ω and τ are mediated by changes in channel geometry. Similarly, headwater reaches of Buckeye Creek developed atop shale and sandstone boulders are statistically distinguishable from downstream reaches wherein corrosion of limestone is the primary means of incision. However, comparisons in each stream reveal that channel geometries, ω and τ, are not strictly controlled by bed solubility. For constant substrate solubility along the Greenbrier River, ω and τ are consistently higher where a bedrock cutbank is present or coarse, insoluble sediment enters the channel. The latter is also associated with locally high values of ω and τ in Buckeye Creek. Assuming that incision by corrosion requires lower values of ω and τ because the channel need not be adjusted for block detachment and tool acceleration, we posit that the statistically lower values of ω and τ are tentative evidence in favor of differential geometric and hydraulic adjustments to substrate resistance. We observe that these adjustments are not made independent of geomorphic setting.

Devonian fluvial strata in and adjacent to the Emsian‐Eifelian Moona Vale Trough, western New South Wales

The lower part of the mid‐Emsian ‐ mid‐Eifelian strata exposed near Moona Vale Station are here called Units 2 and 3 of the Muckabunnya beds (new) whereas the mid‐upper part of these previously unnamed Emsian‐Eifelian strata are represented by the fining‐upwards Menamurtee Sandstone (new). Within this formation lies the largely debris‐flow‐deposited Moona Vale Conglomerate Member (new) which comprises boulders of monomictic sandstone of Devonian aspect derived from an alluvial fan lying west of the Koonenberry Fault. It is inferred that the Menamurtee Sandstone and Unit 3 of the Muckabunnya beds were deposited in the 20 km‐wide active Moona Vale Trough (new), which extended at least 40 km northwards as a pullapart between a northwest‐trending, sinistral Koonenberry Fault and a north‐northeast‐trending sinistral basement fault lying along the trend of the Lake Wintlow Line. In mid‐Eifelian time at the onset of the Tabberabberan Orogenic Pulse, trough growth ceased and continuing sinistral motion (till ?late Givetian time) along the Koonenberry Fault (but probably not along the eastern branch of the Lake Wintlow Line Fault) caused the Menamurtee Anticline (and at least eight other structures) to form in the mapped area east of the Koonenberry Fault. The anticline was then truncated by erosion by mid‐Givetian time and sandstone (Gum Creek beds: new) were deposited unconformably across its truncated crest. In late Givetian to Famennian time the fine‐grained fluvial Ravendale Formation, which crops out west of the Koonenberry Fault in the study area, was deformed during the Kanimblan Orogenic Pulse when the fault was dextral.

A new aquatic species of Verrucaria from alpine Australia

Abstract:Verrucaria cootapatambensis sp. nov. is described from sandstone boulders in an alpine, snow-melt creek in Kosciuszko National Park, New South Wales, Australia. Crown

Lacustrine shore platforms at Lake Waikaremoana, North Island, New Zealand

AbstractThis paper examines the morphology and processes governing the development of shore platforms at Lake Waikaremoana, North Island, New Zealand. Shore platforms at Lake Waikaremoana are recent features, and were formed when a new sequence of shoreline development was initiated, due to lowering of the lake by 5 m in 1946 for hydroelectric power development. Three predominant platform morphologies were identified around the lake. These include gently sloping platforms (c.1·5 to 3·9°), ramp platforms (c.6·8 to 9·2°), and concave ramp platforms (c.7·9 to 12°). Platform widths ranged from 11 to 31 m, with the gently sloping platforms characterized by the widest morphologies. Erosion rates were estimated using perched sandstone boulders and were found to range from 3·4 to 12·5 mm a−1, with a mean erosion rate of 5·9 mm a−1. Higher rates of erosion were identified at lower platform elevations, due to a greater frequency of wetting and drying cycles coincident with storm waves, while lower erosion rates were identified at higher elevations. Field evidence suggests that shore platforms at Lake Waikaremoana were likely initiated and continue to develop as a result of subaerial wetting and drying cycles. Waves, coincident with fluctuating lake levels, play an important role by removing the weathered material from the platforms, and appear to control the width of the platforms. A conceptual model of platform development is presented, and analogies are drawn between this model, and the formation of shore platforms in oceanic environments. Copyright © 2002 John Wiley &amp; Sons, Ltd.

A small glacial cirque basin on Exmoor, Somerset

Geomorphological and sedimentological investigations at the Punchbowl on Exmoor, north Somerset, have demonstrated evidence of cirque basin glaciation, some 30 km south of the accepted southern limit of Anglian ice cover in this area. The Punchbowl is a steep-sided, north-facing basin that has a subdued arcuate ridge at its mouth. Analysis of macrofabrics, clast form and roundness and particle size on sediments forming the ridge indicate it to consist of glacial diamict deposited as a terminal moraine. Further evidence supporting the presence of a former cirque basin glacier at this site is derived from basin morphology and a striated sandstone boulder. Palaeoglacier reconstruction gives a surface area of 0.38 km 2 , a maximum thickness of 46.5 m and a maximum basal shear stress value of 51 kPa. The ELA of the former glacier has been calculated at 334 m OD. There is no evidence for multiple glaciations at this site, and, in the absence of dating controls on the moraine, the glacier is provisionally assumed to have formed during severe climatic conditions associated with the southerly advance of ice sheets during the Anglian cold stage or during the Dimlington Stadial. Development of a glacier at this location appears to have been a rare event during the Quaternary, and may have been facilitated by accumulation of windblown snow from the adjacent plateau.

Variation in foraging activity of Acanthochitona garnoti (Mollusca: Polyplacophora) from different habitats

Foraging activity of Acanthochitona garnoti was studied during spring and neap tides in three different habitats: an aeolian sandstone platform, a permanent high-shore rock pool (aeolian shore) and a quartzitic sandstone boulder shore. On exposed rock, A. garnoti was active only during nocturnal low tides, although some individuals were active during early morning low tides when in shade. Chitons from upper-shore pools were active during both day and night low tides. At all sites chitons foraged for longer (x = 5.5 h) and travelled further (x = 313 mm) during a spring tide new moon and least on a spring tide full moon (x = 4.0 h; x = 182 mm). Chitons on the boulder beach travelled greater distances (x = 367 mm) during foraging than those from aeolian shores (x = 105 mm). It is suggested that this is a result of boulder beach chitons having further to travel to find a grazing patch. Finally, A. garnoti was found to have a ranging pattern of activity on boulder shores and a homing pattern on aeolian s...

Performance of raft foundations for high-rise buildings on the Bouldery Clay in Singapore

The Bouldery Clay in Singapore consists of sandstone boulders that are embedded in a matrix of very stiff to hard silty and sandy clay. The strength and deformation characteristics of the soil matrix are close to those of a weak rock or a heavily overconsolidated clay. The average value of the second cycle moduli from the pressuremeter tests and the plate load tests is 480 MPa, and the average value of the undrained shear strengh from in situ tests is 1000 kPa. The performance of raft foundations for six high-rise buildings founded on the Bouldery Clay has been vary satisfactory, and the measured maximum and differential settlements are within allowable limits. The average equivalent undrained modulus of elasticity back-calculated from settlement observations is 540 MPa, compared with the average modulus of 480 MPa from in situ tests after unloading and reloading. It is therefore recommended that unloading and reloading of at least two cycles should be carried out for in situ tests so that a more representative modulus of elasticity for the Bouldery Clay and other very stiff or hard soil can be obtained. Key words: raft foundations, Bouldery Clay, Young's modulus, settlement, high-rise buildings.

Structure and Seasonal Fluctuations of Rocky Littoral Fish Assemblages in South-Western Portugal: Implications for Otter Prey Availability

The fish assemblages of rocky intertidal and subtidal (&lt;3 m depth) habitats of the south-western Portuguese coast were sampled between May 1992 and November 1993, using traps, angling and hand-netting, to investigate their structure and seasonal dynamics. The main purpose of the study was to describe the patterns of prey availability for marine-feeding otters (Lutra lutra L., Mammalia) in south-western Portugal, and to compare these with other areas in Europe. A total of 475 fish of 14 species was captured over 150 d of trapping (788 trap-days), and 1575 fish of 15 species were captured over 24 d of angling (76.3h). Hand-netting was carried out occasionally, to supplement the observations from the other methods, and only 96 fish of seven species were captured. The three methods yielded different patterns of the fish assemblage: giant gobies (Gobius cobitis Pallas, 33.7%) and rock gobies (G. paganellus L., 22.9%) were the most frequently trapped fish; corkwing wrasse (Symphodus melons (L.), 81.2%) were the usual species caught by angling; shannies (Lipophrys pholis (L.), 42.7%) and Montagu's blennies (Coryphoblennius galerita (L.), 28.1%) were the most frequently netted species. Conger eels (Conger conger (L.)), giant gobies and shannies showed an uneven distribution along the coast, occurring most frequently in schist shelves, rather than in areas of large sandstone boulders. There was a large seasonal variation, with the catches of most species peaking in winter and early spring, including the majority of those most important in the diet of otters: conger eels, shore rocklings (Gaidropsarus mediterraneus L.), rock gobies and corkwing wrasse. This was also the period when the individuals of several species were heaviest.

Constraints on age, erosion, and uplift of Neogene glacial deposits in the Transantarctic Mountains determined from in situ cosmogenic 10Be and 26Al

Research Article| December 01, 1995 Constraints on age, erosion, and uplift of Neogene glacial deposits in the Transantarctic Mountains determined from in situ cosmogenic 10Be and 26Al Edward J. Brook; Edward J. Brook 1Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02540 Search for other works by this author on: GSW Google Scholar Erik T. Brown; Erik T. Brown 2Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Bâtiment 108, 91405, Campus Orsay, France Search for other works by this author on: GSW Google Scholar Mark D. Kurz; Mark D. Kurz 1Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02540 Search for other works by this author on: GSW Google Scholar Robert P. Ackert, Jr; Robert P. Ackert, Jr 1Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02540 Search for other works by this author on: GSW Google Scholar Grant M. Raisbeck; Grant M. Raisbeck 2Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Bâtiment 108, 91405, Campus Orsay, France Search for other works by this author on: GSW Google Scholar Françoise Yiou Françoise Yiou 2Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Bâtiment 108, 91405, Campus Orsay, France Search for other works by this author on: GSW Google Scholar Geology (1995) 23 (12): 1063–1066. https://doi.org/10.1130/0091-7613(1995)023<1063:COAEAU>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Edward J. Brook, Erik T. Brown, Mark D. Kurz, Robert P. Ackert, Grant M. Raisbeck, Françoise Yiou; Constraints on age, erosion, and uplift of Neogene glacial deposits in the Transantarctic Mountains determined from in situ cosmogenic 10Be and 26Al. Geology 1995;; 23 (12): 1063–1066. doi: https://doi.org/10.1130/0091-7613(1995)023<1063:COAEAU>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract 10Be and 26Al data from sandstone boulders in three Neogene glacial deposits in the McMurdo Sound–Dry Valleys region of southern Victoria Land, Antarctica, indicate minimum exposure ages of (Approx.)3 Ma and maximum long-term erosion rates of (Approx.)5–12 cm/m.y., supporting the suggestion that polar desert conditions have persisted in the Dry Valleys since at least late Pliocene time. Variation of cosmogenic nuclide production rate with altitude also allows constraints on past uplift rates. Model calculations employing 10Be data indicate little or no uplift in the Dry Valleys region in the past 3 m.y., precluding rapid (≈1 km/m.y.) late Pliocene uplift previously suggested for some parts of the Transantarctic Mountains. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Influence of colour of substratum on recruitment of spirorbid tubeworms to different types of intertidal boulders

Spirorbid polychaetes recruited to bare, dark grey shale boulders in greater numbers than to bare, light yellow sandstone boulders on the same shore. We examined the influence of colour on recruitment. Manipulative field experiments showed that: (1) more spirorbids recruited to darkcoloured boulders than to light-coloured boulders regardless of the type of rock; (2) the colour of the top of the boulder made little difference to the number of spirorbids recruiting to the undersurface of the boulders; and (3) more spirorbids recruited to shale boulders with darkcoloured undersurfaces than to those with light-coloured undersurfaces regardless of the colour of the top of the boulders. These results highlight the importance of colour as a physical factor affecting the recruitment of spirorbids to initially bare boulders. The colour of boulders did not, however, explain the magnitude of differences in recruitment to sandstone and shale boulders; other physical factors such as surface texture of the boulders may be important. Biological interactions such as the “gregariousness” of spirorbids may amplify initial patterns of recruitment in the short-term but shortages of space may cause spirorbids to recruit to initially unfavourable habitats.