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is widespread in non-poikilitic regions, occurring interstitially between olivine and pyroxene grains. It is the main REE carrier in GRV 99027 and has relatively higher REEs (200-1000 × CI) than that of other lherzolitic shergottites. A REE budget calculation for GRV 99027 yields a whole rock REE pattern very similar to that of other lherzolites. It is characterized by the distinctive light REE depletion and a smooth increase from light REEs to heavy REEs. REE microdistributions in GRV 99027 strongly support the idea that all lherzolitic shergottites formed by identical igneous processes, probably from the same magma chamber on Mars. Despite many similarities in mineralogy, petrography, and trace element geochemistry, subtle differences exist between GRV 99027 and other lherzolitic shergottites. GRV 99027 has relatively uniform mineral compositions (both major elements and REEs), implying that it suffered a higher degree of sub-solidus equilibration than the other three lherzolites. It is notable that GRV 99027 has experienced terrestrial weathering in the Antarctic environment, as its olivine and pyroxenes commonly display a light REE enrichment and a negative Ce anomaly. Caution needs to be taken in future chronological studies.

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Late Quaternary shallow biogenic gas reservoirs have recently been discovered and exploited in the coastal Hangzhou Bay area, northern Zhejiang Province, eastern China. The river in this area strongly incised the underlying old beds during a period of glacial maximum, which resulted in the formation of the Qiantangjiang and the Taihu incised valleys. These incised valleys were filled with fluvial sediments and buried by marine sediments during the postglacial period. Late Quaternary strata of the incised-valley area are composed of four sedimentary facies in ascending order: fluvial floor facies (IV), flood-plain facies (III), sublittoral-marine bay facies (II), and estuarine facies (I).All commercial gas fields occur in flood-plain sand bodies of incised valleys. The bodies are buried 30-60 m (98-197 ft) deep and are 3.0-7.0 m (9.8-23 ft) thick, with a maximum thickness of more than 10 m (33 ft). They are surrounded by impermeable clays. Rapid deposition of overlying sublittoral-marine bay sediments supplied not only abundant gas sources, but also good preservation conditions. The main hydrocarbon sources are dark gray clays of the flood-plain facies and gray muds of the sublittoral-marine bay facies. Sediments of both facies have organic carbon content generally more than 0.4%. Shallow biogenic gas fields and deep gas fields require vastly different drilling and completion techniques. Drilling and completion costs are much lower for the biogenic gas fields.Quaternary incised valleys and flood plains other than Hongzhou Bay in coastal areas of eastern China are promising targets of further exploration for shallow biogenic gas.

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