Rowley Shoals Research Articles

A pre-cursor extensive Miocene reef system to the Rowley Shoals reefs, Western Australia: evidence for structural control of reef growth or natural hydrocarbon seepage?

Numerous Miocene reefs and related carbonate build-ups have been identified in the Rowley Shoals region of the central North West Shelf, offshore Western Australia. The reefs form part of an extensive Miocene reef tract over 1,600 km long, which extended northward into the Browse and Bonaparte basins and southward to North West Cape in the Carnarvon Basin—comparable in length to the modern Great Barrier Reef. Growth of the vast majority of these Miocene reefs failed to keep pace with relative sea-level changes in the latest Miocene, whereas reef growth continued on the central North West Shelf to form the three present-day atolls of the Rowley Shoals: Mermaid, Clerke and Imperieuse reefs. In the Rowley Shoals region, scattered small build-ups and local reef complexes were first established in the Early Miocene, but these build-ups were subsequently terminated at a major Mid Miocene sequence boundary. Widespread buildups and atoll reefs were re-established in the Middle Miocene, and the internal stacking geometries of the reefs appear to relate to distinct growth phases that are correlated with eustatic sea-level fluctuations. These geometries include: a basal aggradational buildup of early Middle Miocene age; a strongly progradational growth phase in the late Middle to early Late Miocene that constructed large reef atolls with infilling lagoon deposits; and a back-stepped aggradational growth phase that formed smaller reef caps in the early–latest Late Miocene. Growth of the majority of the reefs ceased at a major sea-level fall in the Late Miocene (Messinian), and only the reefs of the present-day Rowley Shoals (Mermaid, Clerke and Imperieuse reefs, as well as a drowned shoal to the southwest of Imperieuse Reef) continued to grow after this event. Growth of the Rowley Shoals reefs continued to keep pace with Pliocene-Recent sea-level changes, whereas the surrounding shelf subsided to depths of 230–440 m. We conclude that initial reef growth in the Rowley Shoals region was controlled by transpressional reactivation and structuring of the Mermaid Fault Zone during the early stage of collision between the Australian and Eurasian plates. During this structural reactivation, seabed fault scarps and topographic highs likely provided ideal sites for the initiation of reef growth. The subsequent growth and selective demise of the reefs was controlled by the interplay of eustatic sea-level variations and differential subsidence resulting from continued structural reactivation of the Mermaid Fault Zone. In contrast to models proposed in other regions, there is no direct evidence that active or palaeo hydrocarbon seepage triggered or controlled growth of the Rowley Shoals reefs or their buried Miocene predecessors.

The macromolluscs of Mermaid (Rowley Shoals), Scott and Seringapatam Reefs, Western Australia

– This paper records 339 macromolluscan species comprising 261 gastropods, 70 bivalves, six cephalopods and two chiton species from the north-western Australian atolls of Mermaid Reef (Rowley Shoals), Scott and Seringapatam Reefs.

Station and Transect Data for Mermaid (Rowley Shoals), Scott and Seringapatam Reefs, Western Australia

Station and Transect Data for Mermaid (Rowley Shoals), Scott and Seringapatam Reefs, Western Australia

Subtidal Habitats of Mermaid Reef (Rowley Shoals), Scott and Seringapatam Reefs, Western Australia

Subtidal Habitats of Mermaid Reef (Rowley Shoals), Scott and Seringapatam Reefs, Western Australia

Fishes of three North West Shelf atolls off Western Australia: Mermaid (Rowley Shoals), Scott and Seringapatam Reefs

The biodiversity of fishes on the Australian North West Shelf atolls is known to be the richest in the state. In recent years however, there has been minimal focus on comprehensive taxonomic fish surveys in this region. Since the atolls are subjected to an increasing frequency of pressures such as major cyclones, coral bleaching, tourism, fishing and natural resource exploitation, it is critical to monitor this region to have the information to safeguard the biodiversity for the future. To obtain current data that would complement ongoing quantitative surveys in the region, the Western Australian Museum undertook a taxonomic and semi-quantitative survey of the shallow water reef fishes and other major phyla at Mermaid, Scott and Seringapatam Reefs in September 2006. Thirty nine underwater visual surveys were conducted, supplemented by limited intertidal collecting, angling and surface observations. Analysis of the fish fauna across atolls demonstrated close similarities between North Scott, South Scott and Seringapatam Reefs, and, as a group, these reefs showed certain differences from the more southerly Mermaid Reef. Significant differences were found between lagoonal and outer reef slope habitats. At each atoll, the outer reef slope habitats were more homogeneous and had a greater diversity of fishes than the lagoon habitats, with South Scott lagoon housing a unique mix of both outer reef slope and lagoon species. Fish diversity was found to increase towards the northern atolls, supporting previous research in the region. The fish fauna at all four atolls had more in common with fish assemblages at equivalent clear-water reefs in Indonesia than with those on the northwest coastal mainland and, as such, are unique within Western Australian waters.

Marine Benthic Plants of Western Australia’s Shelf-Edge Atolls

One hundred and twenty-one species of marine algae, seagrasses and cyanobacteria are reported from the offshore atolls of northwestern Western Australia (the Rowley Shoals, Scott Reef and Seringapatam Reef). Included are 65 species of Rhodophyta, 40 species of Chlorophyta, nine species of Phaeophyceae, three species of Cyanophyta and four species of seagrasses. This report presents the first detailed account of marine benthic algae from these atolls. Twenty-four species are newly recorded for Western Australia, with four species (Anadyomene wrightii, Rhipilia nigrescens, Ceramium krameri and Zellera tawallina) also newly recorded for Australia.

Crustaceans of Mermaid (Rowley Shoals), Scott and Seringapatam Reefs, north Western Australia

– The atolls on the north-western Australian continental shelf are recognised in having a diverse shallow-water fauna with many widely distributed Indo-West Pacific species. However, the crustaceans of these reefs are poorly known.

A revision of the marine eel-tailed catfish genus 'Euristhmus' (Teleostei: Siluriformes: Plotosidae)

The Indo-west Pacific plotosid catfish genus Euristhmus Ogilby is revised and found to include five species: E. lepturus (G nther) occurs along the eastern and northern parts of Australia, from Sydney to the Gulf of Carpentaria; E. microceps (Richardson) is reported from Shark Bay, Western Australia to Goulburn Islands, Northern Territory; and E. nudiceps (G nther), the most widely distributed species, extends along the northern margin of Australia, from Exmouth Bay, Western Australia to Moreton Bay, Queensland. Two new species are described herein: E. microphthalmus, from coastal regions of the Northern Territory, Australia and West Papua, Indonesia; and E. sandrae from the vicinity of Rowley Shoals and Exmouth Gulf, Western Australia. Exilichthys Whitley is a junior synonym of Euristhmus; Cnidoglanis microcephalus G nther is an unnecessary replacement name for E. microceps; and Plotosus elongatus Castelnau is a junior subjective synonym of E. lepturus. A lectotype is designated for Cnidoglanis lepturus G nther.

Three new Australian species of the fish genus Xenisthmus (Gobioidei: Xenisthmidae)

Xenisthmus chi n.sp., described from two specimens from Rowley Shoals, Timor Sea, has in combination: second dorsal-fin rays I,12; anal-fin rays I,11; predorsal area with narrow median wedge of scales extending forward almost to pore D; posterior naris without flap; and head and body pale with brown reticulate mottling, forming about 11 X-shaped markings along sides between pectoral- and caudal-fin bases. Xenisthmus eirospilus n.sp., described from 15 specimens from throughout the southwest Pacific (type locality Elizabeth Reef, Tasman Sea), has in combination: second dorsal-fin rays I,12-13, usually I,12; anal-fin rays I,11-12, usually I,11; vertebrae 10 + 17; tongue indented; posterior naris with well-developed flap; upper sides of body with 12 large closely spaced spots, which usually do not extend to dorsal edge of body; and predorsal scaled to vertical through posterior edge of preopercle. Xenisthmus semicinctus n.sp., described from two specimens from Rowley Shoals, Timor Sea, has in combination: second dorsal-fin rays I,12; anal-fin rays I,11; vertebrae 10 + 17; tongue indented; posterior naris with well-developed flap; upper sides of body with 12 large, closely spaced spots, each connecting dorsally to, or almost to, mid-line by short, dark bar; and predorsal area with narrow median wedge of scales extending forward almost to pore D.

Fishes of the Dampier Archipelago, Western Australia

The shallow-water fish fauna of the Dampier Archipelago (to a depth of 30 m), which now totals 650 species, consists of a rich coral reef fauna (465 species), a moderate mangrove one (116 species), smaller numbers of soft bottom inhabitants (106 species) and a relatively low number of pelagic species (67). The outer islands are inhabited predominantly by coral reef fishes whereas inner areas close to the mainland are occupied by mangrove and silty-bottom dwellers. The inter-island passages have a relatively rich soft bottom fauna. Species diversity is at its highest in areas of high topographic diversity, the area with the highest diversities lying along the exposed northern perimeter of the archipelago. These more off-shore areas are apparently under the direct influence of the off-shore flowing, warm Leeuwin Current, where water clarity is high and propagules from upstream locations, such as the Rowley Shoals, are deposited. The more in-shore areas are affected by high turbidity resulting from mangrove communities and high freshwater runoff during cyclonic events. The fish fauna of the archipelago is closely related to that occurring at the more off-shore Monte Bello Islands, but is noticeably less diverse than the islands of the West Pilbara region to the south. Some elements of the Kimberley fish fauna also inhabit the archipelago.

Lack of imposex in the muricid Morula granulate from Rowley Shoals, northwestern Australia

Dissection of 197 specimens of the thaid Morula granulata from Rowley Shoals, on the outer continental shelf 300 km west of Broome, northwestern Australia, revealed that none were affected by imposex. While imposex is known to be caused by tributyltin (TBT), there are also other possible causes such as copper, paint matrix and environmental factors. In addition to the relatively low TBT levels in their tissue, the other environmental factors which can cause imposex may also be missing from Bedwell Island.

Excavatolides N - T, New Briaran Diterpenes from the Western Australian Gorgonian Briareum excavatum

A Western Australian sample of the gorgonian Briareum excavatum, collected at Rowley Shoals, afforded one known (10) and seven new briaran diterpenes (1), (3) and (5)–(9). Gross structures and relative stereochemistries were determined by spectroscopic methods and by comparison of spectral data with those of previously reported briarans. Support for a proposed conformation of the 10-membered ring (stabilized by hydrogen-bonding) to explain atypical 1H n.m.r. chemical shifts and coupling constants in (9) was obtained from energy minimization of the proposed structure by an ab initio density functional method.

A new species of psychrolutid fish from western Australia

Psychrolutes occidentalis, a new species of psychrolutid fish, is described from mud bottoms at depths of 350–740 m on the continental slopes around Rowley Shoals, northwestern Australia. The new species is illustrated and compared with other species of the genusPsychrolutes. It differs from other species in the following characters: 14–15 dorsal soft rays, 21–23 pectoral rays, 30–31 vertebrae, no cirri on head and body, lateral line not emerging through tubes, and reddish brown head and body color with darker brown marblings. Aspects of the zoogeography of this new species from the tropical region and of the other species ofPsychrolutes are discussed.

Late Cenozoic sedimentary forms on the northwest Australian continental shelf

Little terrigenous detritus is supplied to the broad northwest Australian continental shelf which, in common with many other shelves, is a zone of winnowing and transport rather than deposition. Shallow seismic reflexion profiles across the shelf and upper continental slope reveal apparent gentle warping of the Late Cenozoic sediments and at least three erosional surfaces above a disconformity identified with the important regional Late Miocene hiatus. The Late Miocene erosion surface is believed to be relatively flat-lying over quite wide areas and to crop out on the upper continental slope at 240 m water depth south of the Rowley Shoals. The Rowley Shoals themselves stand on a gently sloping terrace which is believed to be an expression of this same surface downwarped to about 400 m. The outer edge of the shelf south of the Rowley Shoals supports a long low ridge apparently consisting of fine-grained sediment and Globigerina sand. Seismic evidence indicates that this ridge is a constructional sedimentary body unrelated to submerged land forms or to offshore bars. It rests on a flat-lying channelled surface of erosion and marks a zone of maximum accumulation of pelagic material and fine sediment winnowed from the shelf. Such sediment normally is deposited in much deeper water on the continental slope. Other plano-convex lenses of sediment probably occur deeper in the Late Ceinozoic sedimentary sequence on the continental shelf and might be misinterpreted as structural deformation.

Cartier Furrow, a Major Structure along the Continental Margin of North-western Australia

A COMPILATION of recent aeromagnetic surveys in offshore north-western Australia1–4 (Fig. 1) reveals a furrow in the magnetic basement, which I propose to call the Cartier Furrow, after Cartier Island. The furrow is at least 1,250 km long, and 6 km deep, and is filled with sediment. It underlies the upper continental slope except where it crosses the Londonderry Rise, which is a spur in the continental shelf. The furrow is bounded on its south-eastern side by the offshore Bonaparte Gulf Basin in the north, by the offshore Canning Basin in the south, and, in between, by a prism of non-magnetic rocks which thin south-eastward towards the Pre-Cambrian Kimberley Block. The north-western side of the furrow is marked by the atolls of the Rowley Shoals, Scott Reef, and Seringapatam Reef, which rise from the continental slope; by the outer part of the Londonderry Rise, which is crowned by the reefs of Ashmore Island, Cartier Island and Hibernia Reef; and by the south-east slope of the Timor Trough. From a comparison with onshore surveys in the Bonaparte Gulf Basin, Veevers and van Andel5 identified the magnetic basement beneath the Sahul Shelf as either a layer or layers high in the Pre-Cambrian of the Kimberley Block, or Lower Cambrian volcanics. The magnetic basement in the landward part of the Canning Basin6, as shown by drill holes, is crystalline Pre-Cambrian rock (granite or metamorphics), so that the magnetic basement offshore probably coincides also with the surface of Pre-Cambrian rocks.

Societies and Academies

SYDNEY Linnean Society of New South Wales, July 26.—The following papers were read:—Botanical notes in Queensland, Part 3, by the Rev. J. E. Tenison-Woods, F G.S. This paper contained the results of the author's observations on the Mulgrave River, with a list of the species collected by him in that district.—On the forage plants indigenous to New South Wales, by Dr. Woolls, F.L.S.—Description of three new fishes of Queensland, by Chas. W. De Vis, B.A. The species described by Mr. De Vis are:—1. Oligorus Goliath, taken in Moreton Bay, a fish of gigantic size, seven feet long, and two feet high. 2. Synaptura Fitzroienis from Rockhampton; and 3. Engraulis Carpentariæ:, from the Norman River.—4. Description of a species of Squill, Lysiosquilla Mitrsii, from Moreton Bay, by Chas. W. De Vis, B.A. This Crustacean, which is found in Moreton Bay, differs materially, according to Mr. De Vis, from the two species of the same genus recorded in Mr. Haswell's Catalogue, which belong to Mr. Mirs' second section of the genus, while the present species agrees with his fir?t section.—On Cypræa citrina Gray, from Rowley Shoals, North West Australia, by John Brazier. C.M.Z.S.—On a variety of Ovulum depressum, from the Loyalty Islands, by Mr. R. C. Rossiter.—Notes on the nidification of the spoon-bill, the heron, and the night-heron, by Mr. K. H. Bennett.