大西洋扇贝贝壳生长年轮的氧同位素研究

两只活的大洋扇贝Placopecten magellanicus分别于1983和1985年采自加拿大诺瓦·斯科舍省布朗斯浅滩,其氧同位素记录展示出一种年度性的循环,并与由环境海水的实测温度和同位素组成所预计的贝壳同位素组成十分接近。外生长线的位置与这些循环中δ~(18)O的最大值吻合,这说明外生长线于底层海水温度最低时(春季)形成。据测定的δ~(18)O的结果证明,外生长线是年度性形成的,这与生物学证据一致。     

澳大利亚海岸概况

澳大利亚是个大陆岛,界于南纬11°—43°,东西长5000公里,面积约770万平方公里(包括塔斯马尼亚岛等)。她与南极大陆隔以3000公里的海域。在澳大利亚和亚洲大陆之间有一列岛屿,其中新几内亚位于与澳大利亚相同的大陆架上,在第四纪时通常是相连的。     

由偏顶蛤贝壳中稳定同位素剖面追溯海水温度记录

本文用在加拿大诺瓦·斯科舍省芬克湾采集到的两只活体偏顶蛤(Modiolus)贝壳上的氧同位素组成重建了过去十年间的底层海水温度记录,它也可作为一种独立的方法来确定贝壳上外生长线的沉积时间。由于对贝壳进行了密集采样(可多至每个贝壳沉积年份取15个样品),贝壳上的δ~(16)O变化反映了芬克湾底层海水的季节性变化。两只贝壳所得的温度剖面符合得很好,说明它们基本上是与真实的环境温度相对应的。本研究证明在海胆疾病爆发时底层海水的温度并没有异常升高,这说明疾病传播的关键因素是带病的生物体,而不是温度。同位素技术也说明了在贝壳外表面上可见的外生长线是年轮性的,它们是在每年冬季最低水温时沉积出来的。     

Population structure of Haliotis rubra from South Australia inferred from nuclear and mtDNA analyses

1Introduction ThemajorityofAustralia’sabalonefisheryex ports(5.135kt,worth＄216millionin2002～2003,ABARE2004)consistofblacklipabalone(HaliotisrubraLeach,1814).AssuchH.rubrais consideredasanimportantmarineresourcewithin Australia.Likemanyabalonespecieswor…     

一个与转移作用有关的盆地的演化：Ardea盆地（意大利中部拉齐奥地区）

一个与转移作用有关的盆地的演化：Ａｒｄｅａ盆地（意大利中部拉齐奥地区）Ｃ．Ｆａｃｃｅｎｎａ等地层Ａｒｄｅａ盆地是拉齐奥边缘最深的盆地之一。充填了１６００ｍ中新－更新统沉积。这套沉积物覆盖在一套中新统以泥灰质－砂泥质为主的复理石异地构造层上，复理石上覆...     

In-Situ Observation of Fluid Mud in the North Passage of Yangtze Estuary, China

Observations of fluid mud were made in the lower North Passage of the Yangtze Estuary in February 2000, on 10 -11 August 2000, on 30 - 31 August 2000 (after two strong typhoons), on 21 - 24 August 2000 (neap tide) and on 3 -6 September 2000 (mean tide) respectively. In situ data show that the fluid mud in this area consists of fine cohesive sediment (median size 7.23 μm). The formation and movement of fluid mud varied during the neap-spring and flood-ebb tidal cycle. Observations suggest that fluid mud phenomena in this area may be categorised in a three-fold manner as slack water, storm and saltwedge features. The thickness of the fluid mud layer of slack water during the neap tide ranged from 0.2 to 0.96 m, whereas during the mean tide, the thickness ranged from 0.17 to 0.73 m, and the thickness of the fluid mud layer was larger during slack water than at the flood peak. Shoals cover an area of 800 km^2 with a water depth smaller than 5 m. Erosion of these extensive intertidal mudflats due to storm action provides an abundant sediment source. This is particularly significant in this estuary when the tidal level is lower than 5 m. The lower North Passage is a typical zone of saltwater wedging, so the saltwedge fluid mud has the most extensive spatial range in the estuary.