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In the Miocene sandstones of the Nankang Formation in north-eastern Taiwan, different varieties of the trace fossilOphiomorphaare abundant. In certain beds, a peculiar reworking of verticalOphiomorphashafts was observed. This reworking consists of an inner, lined tube positioned in the centre of the shaft. The shaft is lined by thin walls with small knobs and is distinctly different from the shafts of theOphiomorpha nodosamazes found in the same beds which have thick walls and large knobs. Because both outer and the inner tube walls were constructed by small sub-pellets, a diagenetic origin can be ruled out. The presence of sub-pellets further indicates that the inner tubes were also constructed by crustaceans and not commensal organisms such as worms or fish. The abundance of these vertical shafts suggests that they were constructed for a specific purpose, and the similarities in sub-pellets indicate that they likely were constructed by different generations of the same crustacean species. Because brooding chambers were not observed and are rare among extant marine crustaceans, we suggest that the vertical shafts were constructed to encourage juvenile shrimp to resettle in the parental burrows after they had completed their pelagic larval stages. [ABSTRACT FROM AUTHOR]

The formation, evolution, and potential as a climate archive of Tienchi Pond was evaluated using geomorphology, sedimentology, geochemistry, and AMS radiocarbon measurements of tree ring cores. Tienchi Pond is a small ephemeral lake situated on the subtropical Lanyu Island in the Western Pacific Ocean about 90 km east of southern Taiwan. The lake is situated on a mountain ridge and is today characterized by numerous dead trees and stumps. The position at the boundary between the two main components of the SE Asian monsoon system, the Asian landmass and the Western Pacific, makes this lake particularly interesting as a potential natural climate archive. Since previous studies have shown that the bedrock underlying the lake formed over 2 my ago, a volcanic crater origin was ruled out. Rather, element ratios of K/Ti and Ca/Fe together with 210 Pb dating suggest a recent origin for the lake, probably as the result of a natural damming event in the southern, narrower, part of the lake basin, or as a result of increased precipitation at the end of the Little Ice Age (or a combination of both). Radiocarbon measurements on a dead tree near the lake perimeter show 14 C levels of more than 1.7% modern radiocarbon near the bark, suggesting that the tree died in the early 1970s. In contrast, by correlating a large number of radiocarbon measurements to a northern hemisphere reference curve, it was shown that trees closer to the center of the lake died in the early 20th century. This agrees with a scenario where a small lake formed by initial damming, and gradually grew larger through erosion of the surrounding shore lines caused by rapid lake level oscillations. [ABSTRACT FROM AUTHOR]