摘要
Ｄｅｖｉｌｓ岩洞５０万年气候记录所反映的气候轮回似乎不存在准周期性变化。Ｂｒｏｅｃｋｅｒ认为，ＤＨ－１１δ￣（１８）Ｏ序列的定年分析是空前出色的。倒数第二次冰期结束时间虽然比深海记录仅早了１．７万年，却足以构成对Ｍｉｌａｎｋｏｖｉｔｃｈ理论的挑战。Ｓｈａｃｋｌｅｔｏｎ反驳说，由于Ｄｅｖｉｌｓ裂隙一直充满着水，水中过量的￣（２３０）Ｔｈ造成断代误差高达５千年。Ｉｍｂｒｉｅ的分析表明，如果把Ｄｅｖｉｌｓ年代强加于洋海记录，则必需改变深海沉积速度。而这是难以令人置信的。因此把它直接转移到深海记录上也是不适当的。Ｅｍｉｌｉａｎｉ指出，冰期结束时间是一段过渡时期，并不适合作为更新世气候转折的准确时间标志，而δ￣（１８）Ｏ曲线的峰值和谷值才适合用于时间序列的对比分析。Ｇａｌｌａｐ等对Ｂａｒｂａｄｏｓ阶地形成时间的深入论证表明，近２０万年以来，所有高海平面均与北纬６５°Ｎ夏季日照峰值相对应，证明全球气候变化为轨道变化所驱动。Ｃｒｏｗｌｅｙ则认为Ｄｅｖｉｌｓ岩洞与深海沉积两者的年代都是正确的。至于倒数第二次冰期鼎盛时期之后的转暖时间两者出现的不一致性应理解为南伸冰盖第一阶段退缩引起的副极锋的北撤导致的Ｄｅｖｉｌｓ区域变暖所?
A continuous 500 kyr climate record from vein calcite in Devils Hole,Ncvada shows that the duration of the last four glacial cycles increased from 80 kyr．to 130 kyr．This variationindicates that major climate changes were aperiodic. Broecker（1992）questioned the validityof the Milankovitch theory．He suggested that althouth the date of the end of the penultimateice age（termination 11）was only 17 kyr．earlier than the previously accepted date of 128 kyr.this change is enough to bring the Milankovitch mechanism into serious deubt. Shackleton （1993） refuted the argument．He commented that the discrepancy arises dat-ing of the Devils Hole calcite vein by measuring the growth of^(230)Th from its parent ^(234)U,be-cause^(230)Th is produced by decay ofdissolved^(234)U in the water． Additionally， the value of 140±3ka was deteimined by interpolation between the closest directly dated subsamples（132 ±3and 150±3ka）。Imbrie（1993）demonstrated that applying the Devils Hole chronology to ocean cores re-quires physically implausible changes in sedimentation rate，therefor transfer it to the marinerecord is inappropriate，And the evidence in favour ofmilankovith theory remains strong. Emiliani（1993）suggested that terminations，transitional episodes which extend throughtime，are poor time markers for the correlation of pleistocene section， The maxima（hypsithermals）and especially the minima（bathytherinals）in the isotope curves are muchsharuer and thus afford a more precise correlation. The astronomical parameters can triggeronly the initiation of an ice age，further development of glaciation and deglaciation is drivenby the internal dynamics of the ice－ocean－atmosphere system．The timing of high sea levels over the past 200 kyr．（Gallup et al．，1994）concluded thatfor the last three interglacial and two intervening interstadial rteriods，sea level peaked at orafter peaks in summer insolation in the Northern Hemisphere. This overall patternsupportsthe idea that glacial-interglacial cycles are caused by changes in Earth＇s orbital geometry．Crowley suggests that both the Devils Hole and deep－sea chronologies may be correct，with differences between 130 ka and 150 ka years ago reflecting a regionally varying to cli-mate shifts associated with a very extensive glaciation. And extending the vostok ice-core re-cord back to the penultimate glacial period（～140－200 ka ago）yields a new glaciologicaltimescale which is consistent with ocean records．
出处
《冰川冻土》
CSCD
北大核心
1994年第4期363-370,共8页
Journal of Glaciology and Geocryology
关键词
MILANKOVITCH
理论
海洋
陆地
气候记录
： Milankovitch theory，marine and land－based climate records，timing ofhighsea levels
