(Table 1) Summary of accelerator mass spectrometer (AMS) radiocarbon ages in ODP Sites 169-1033 and 169-1034@en

Continuous coring in Saanich Inlet (Ocean Drilling Program, ODP Leg 169S), British Columbia, Canada, yielded a detailed record of Late Quaternary climate, oceanography, marine productivity, and terrestrial vegetation. Two sites (1033 and 1034) were drilled to maximum depths of 105 and 118 m, recovering sediments ranging in age from 13,300 to less than 300 14C yr. Earliest sediments consist of dense, largely massive, gray glaciomarine muds with dropstones and sand and silt laminae deposited during the waning stages of glaciation. Deposition of organic-rich olive gray sediments began in the fjord about 12,000 14C yr ago, under well-oxygenated conditions as reflected by the presence of bioturbation and a diverse infaunal bivalve community. At about 10,500 14C yr, a massive, gray unit, 40-50 cm thick, was emplaced in a very short span of time. The unit is marked by a sharp lower contact, a gradational upper contact and an abundance of reworked Tertiary microfossils. It has been interpreted as resulting from massive flood events caused by the collapse of glacial dams in the Fraser Valley of mainland British Columbia. Progressively greater anoxia in bottom waters of Saanich Inlet began about 7000 14C yr ago. This is reflected in the preservation of varved sediments consisting of diatomaceous spring-summer laminae and terrigenous winter laminae. Correlation of the sediments was based on: marked lithologic changes, the presence of massive intervals (reflecting localized sediment gravity flow events), the Mazama Ash, occasional thin gray laminae (indicative of abnormal flood events in nearby watersheds), varve counts between marker horizons, and 71 accelerator mass spectrometry (AMS) radiocarbon dates.加拿大不列颠哥伦比亚省的萨尼奇湾（Saanich Inlet）海洋钻探计划（Ocean Drilling Program, ODP）第169S航次的连续取芯工作，获取了晚第四纪气候、海洋学、海洋生产力及陆地植被的高分辨率详细记录。本次钻探共布设两个站位（1033与1034），最大取芯深度分别达105米与118米，所获沉积物的年代跨度为13300年至不足300个放射性碳年（¹⁴C yr）。最底部的沉积物为致密、整体呈块状的灰色冰海泥，含有坠石及砂、粉砂纹层，沉积于冰期消退阶段。约12000个放射性碳年之前，该峡湾内开始沉积富含有机质的橄榄灰色沉积物，当时水体氧化条件良好，这一特征可通过生物扰动现象及多样的内生双壳类群落得到印证。约10500个放射性碳年时，一套厚度40~50厘米的块状灰色沉积单元在极短时间内形成，该单元以清晰的底部接触界面、渐变的顶部接触界面以及大量再沉积的第三纪微化石为典型特征，被认为是由不列颠哥伦比亚大陆弗雷泽河谷（Fraser Valley）冰川坝坍塌引发的大规模洪水事件所形成。约7000个放射性碳年之前，萨尼奇湾底层水体的缺氧程度逐渐加剧，这一点可通过纹层沉积物的保存状态得到反映：该沉积物由硅藻质春夏纹层与陆源冬季纹层组成。沉积物对比依据如下：显著的岩性变化、块状沉积层段（反映局地沉积物重力流事件）、马扎马火山灰（Mazama Ash）、偶见的灰色薄纹层（指示邻近流域的异常洪水事件）、标志层之间的纹层计数，以及71个加速器质谱（accelerator mass spectrometry, AMS）放射性碳测年数据。