Crocker Range Research Articles

クロッカーレンジ国立公園（マレーシア、サバ州）に生息するボルネオミツバチの遺伝的多様性とその起源

クロッカーレンジ国立公園（マレーシア、サバ州）に生息するボルネオミツバチの遺伝的多様性とその起源

The Gomantong Limestone of eastern Borneo: a sedimentological comparison with the near-contemporaneous Luconia Province

The Luconia Province, lying to the North of Borneo, is an important hydrocarbon-bearing province. Faulting in the Oligo–Miocene led to the uplift of a series of blocks, upon which at least 240 carbonate build-ups were developed in the late Lower to Middle Miocene. As part of the search for appropriate analogues, an extensive field study was undertaken on the slightly older to contemporaneous Gomantong Limestone, which outcrops in eastern Sabah, some 800 km to the east of the Luconia Province. In eastern Sabah, southeast of the Crocker Range, Eocene to Miocene clastic and subordinate carbonate sedimentary rocks were deposited in a large east–west trending foreland basin. The Gomantong Limestone outcrops in the eastern third of this basin, the Central Sabah Basin, and is interpreted as having been deposited in shallower shoaling portions of the basin. Exposure is limited to isolated outcrops of deformed, often overturned or steeply dipping, carbonates. The studied localities form a linear trend extending some 50 km in a SSW–NNE orientation. The bulk of the limestone consists of coral-dominated framestones and boundstones and associated fore-reef and open marine facies. Coral morphology, foraminiferal/coralline red algal content and detailed sedimentological observations enabled an interpretation of the depositional settings of these carbonates to be made. The varied carbonate deposits were then interpreted in terms of palaeobathymetry. A very rich fauna is present throughout the formation, with some intervals dominated by large benthic foraminifera, particularly Lepidocyclina. These indicate a Chattian to Burdigalian age. Interpreted depositional environments range from open marine shelfal marls to a variety of reef-associated deposits. These have been subdivided on the basis of the dominant component: corals, coralline algae, foraminifera or siliciclastic components. Limited burial of these carbonates has resulted in excellent preservation of these sediments with very little diagenetic alteration. The Gomantong Limestone is interpreted to have been deposited in an open shelf setting, adjacent to an east–west trending shoreline. This shoreline bordered a palaeohigh within the foreland basin, and the basin is interpreted to have deepened to the north. This is in extreme contrast to the isolated carbonate build-ups in the Luconia Province to the west. Similarities in primary facies can be observed, and both the Gomantong Limestone and Luconia Province exhibit evidence of drowning events, but the facies are affected by very different diagenetic histories, which have left the two provinces with completely different reservoir characteristics. The disparity in secondary alteration shows the tremendous importance of diagenesis on the development of porosity in carbonates.

Neogene arc-continent collision in Sabah, Northern Borneo (Malaysia)—Reply

Abstract The Neogene evolution of Sabah can be interpreted in terms of an arc-continent collision initiated during early Middle Miocene time and followed by intraplate shortening, the latter being active in this area at the present day. The volcanic arc of Late Oligocene-Middle Miocene age is imbricated with melanges and thrust northwestward on a polyphase-deformed turbiditic sequence of Late Cretaceous-Middle Miocene age (Crocker Range). Intraplate shortening is seen in the thrusting and folding offshore Sabah along the Palawan-North Borneo Trench, and also by broad open folds and strike-slip faulting in the previously sutured terranes. This collision can either be interpreted as the final stage of southward subduction of the hypothetical Proto-South China Sea, or the result of back thrusting of the Sulu volcanic arc resulting from the subduction of the Celebes Sea toward the north.

Neogene arc-continent collision in Sabah, Northern Borneo (Malaysia)

The Neogene evolution of Sabah can be interpreted in terms of an arc-continent collision initiated during early Middle Miocene time and followed by intraplate shortening, the latter being active in this area at the present day. The volcanic arc of Late Oligocene-Middle Miocene age is imbricated with melanges and thrust northwestward on a polyphase-deformed turbiditic sequence of Late Cretaceous-Middle Miocene age (Crocker Range). Intraplate shortening is seen in the thrusting and folding offshore Sabah along the Palawan-North Borneo Trench, and also by broad open folds and strike-slip faulting in the previously sutured terranes. This collision can either be interpreted as the final stage of southward subduction of the hypothetical Proto-South China Sea, or the result of back thrusting of the Sulu volcanic arc resulting from the subduction of the Celebes Sea toward the north.

Pollination of Rafflesia (Rafflesiaceae)

The genus Rqfflesia includes about 13 species of parasitic flowering plants, among which are the largest known flowers. The flower with subtending scales is the only part of the plant external to the host and is produced solitary on roots (rarely stems) of the genus Tetrastigma (Vitaceae). Field studies were made of the pollination process in R. pricei, a species endemic to the Crocker Range in the Malaysian state of Sabah (northern Borneo). Pollination is mediated by carrion (bluebottle) flies of the genera Lucilla and Chrysomya. Experimental data indicate that both visual and olfactory cues are important in attracting flies to flowers. Flies (mostly female L. papuensis) obtain loads of the viscous liquid pollen matrix by visiting male flowers and entering anther grooves on the central column of the flower, precisely guided by ridges armed with hairs that force the fly into a position in which the pollen is positioned on the dorsal part of the thorax. “Windows” on the inside of the perigone diaphragm apparently help orient their flight inside flowers. Pollen-loaded flies visiting female flowers may enter the infradiscoidal sulcus formed by a broad ring of stigmatic tissue above and the expanded base of the column below. On entering the sulcus the fly is wedged in so tightly that pollen is rubbed off the thorax onto the stigma. Only large flies could be effective in picking up pollen from male flowers and transferring it to female flowers. The pollination syndrome is sapromyophily, in which the flower closely parallels trap flowers of several other plant families, although it is not a trap. The flower provides no reward for pollinators but deceives them by an apparent offering of food and possibly brood place. Rafflesia plants are extremely rare, perhaps in part because of infrequency of pollination, which requires neighboring male and female flowers simultaneously in bloom.

POLLINATION OF RAFFLESIA (RAFFLESIACEAE)

The genus Rqfflesia includes about 13 species of parasitic flowering plants, among which are the largest known flowers. The flower with subtending scales is the only part of the plant external to the host and is produced solitary on roots (rarely stems) of the genus Tetrastigma (Vitaceae). Field studies were made of the pollination process in R. pricei, a species endemic to the Crocker Range in the Malaysian state of Sabah (northern Borneo). Pollination is mediated by carrion (bluebottle) flies of the genera Lucilla and Chrysomya. Experimental data indicate that both visual and olfactory cues are important in attracting flies to flowers. Flies (mostly female L. papuensis) obtain loads of the viscous liquid pollen matrix by visiting male flowers and entering anther grooves on the central column of the flower, precisely guided by ridges armed with hairs that force the fly into a position in which the pollen is positioned on the dorsal part of the thorax. “Windows” on the inside of the perigone diaphragm apparently help orient their flight inside flowers. Pollen‐loaded flies visiting female flowers may enter the infradiscoidal sulcus formed by a broad ring of stigmatic tissue above and the expanded base of the column below. On entering the sulcus the fly is wedged in so tightly that pollen is rubbed off the thorax onto the stigma. Only large flies could be effective in picking up pollen from male flowers and transferring it to female flowers. The pollination syndrome is sapromyophily, in which the flower closely parallels trap flowers of several other plant families, although it is not a trap. The flower provides no reward for pollinators but deceives them by an apparent offering of food and possibly brood place. Rafflesia plants are extremely rare, perhaps in part because of infrequency of pollination, which requires neighboring male and female flowers simultaneously in bloom.