{"title":"Record of palaeoclimate across the Cretaceous–Palaeogene boundary from palaeosols in the west-central San Juan Basin, New Mexico, USA","authors":"Lawrence H. Tanner, Spencer G. Lucas","doi":"10.1002/dep2.251","DOIUrl":null,"url":null,"abstract":"<p>The mass extinction at the Cretaceous–Palaeogene boundary is widely attributed to sudden and severe climate changes forced by bolide impact and/or flood basalt volcanism. In terrestrial depositional settings, these changes may potentially be recorded by palaeosols. To test the ability of pedogenic features to record both long-term climate and shorter-term changes preceding and following the Cretaceous–Palaeogene extinction event, palaeosols in the Upper Cretaceous (Maastrichtian) Naashoibito Member of the Ojo Alamo Formation and the lower Palaeocene (Danian) Nacimiento Formation in the San Juan Basin of north-western New Mexico, USA, were examined, including data from previous studies. The fine-grained facies of the Naashoibito Member comprises grey to greenish-grey and red-banded mudstones displaying pedogenic features including colour mottling, root traces, cutans, ped fabrics, pedogenic slickensides and calcareous nodules. Aside from a high-chroma horizon at the formation base, palaeosols in the lower Nacimiento Formation are broadly similar to those observed in the Naashoibito Member. Lateral and vertical variability of the pedogenic features between correlated sections suggest that soil hydrology varied spatially and temporally from very saturated to seasonally well-drained, with temporal variations controlled by basin sedimentation rates. Abrupt and/or catastrophic climate events precisely at the Cretaceous–Palaeogene boundary are not recorded due to an unconformity at the top of the Naashoibito Member. However, the presence of kaolinite in the clay mineral assemblage of the Nacimiento Formation, particularly near the formation base, but not in the Naashoibito Member, indicates episodic warmth and short (10<sup>4</sup> years) intervals of more intense weathering conditions during the very early Danian as compared to the late Maastrichtian. Aside from short warm intervals, the overall palaeoclimate during deposition of both formations was warm and consistently subhumid to humid and seasonal, suggesting no substantial long-term (10<sup>5</sup>–10<sup>6</sup>) climate change took place across the Cretaceous–Palaeogene boundary in the San Juan Basin.</p>","PeriodicalId":54144,"journal":{"name":"Depositional Record","volume":null,"pages":null},"PeriodicalIF":1.9000,"publicationDate":"2023-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/dep2.251","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Depositional Record","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1002/dep2.251","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
The mass extinction at the Cretaceous–Palaeogene boundary is widely attributed to sudden and severe climate changes forced by bolide impact and/or flood basalt volcanism. In terrestrial depositional settings, these changes may potentially be recorded by palaeosols. To test the ability of pedogenic features to record both long-term climate and shorter-term changes preceding and following the Cretaceous–Palaeogene extinction event, palaeosols in the Upper Cretaceous (Maastrichtian) Naashoibito Member of the Ojo Alamo Formation and the lower Palaeocene (Danian) Nacimiento Formation in the San Juan Basin of north-western New Mexico, USA, were examined, including data from previous studies. The fine-grained facies of the Naashoibito Member comprises grey to greenish-grey and red-banded mudstones displaying pedogenic features including colour mottling, root traces, cutans, ped fabrics, pedogenic slickensides and calcareous nodules. Aside from a high-chroma horizon at the formation base, palaeosols in the lower Nacimiento Formation are broadly similar to those observed in the Naashoibito Member. Lateral and vertical variability of the pedogenic features between correlated sections suggest that soil hydrology varied spatially and temporally from very saturated to seasonally well-drained, with temporal variations controlled by basin sedimentation rates. Abrupt and/or catastrophic climate events precisely at the Cretaceous–Palaeogene boundary are not recorded due to an unconformity at the top of the Naashoibito Member. However, the presence of kaolinite in the clay mineral assemblage of the Nacimiento Formation, particularly near the formation base, but not in the Naashoibito Member, indicates episodic warmth and short (104 years) intervals of more intense weathering conditions during the very early Danian as compared to the late Maastrichtian. Aside from short warm intervals, the overall palaeoclimate during deposition of both formations was warm and consistently subhumid to humid and seasonal, suggesting no substantial long-term (105–106) climate change took place across the Cretaceous–Palaeogene boundary in the San Juan Basin.
白垩纪-古近纪边界的大灭绝被广泛归因于由火流星撞击和/或洪水玄武岩火山作用造成的突然和严重的气候变化。在陆相沉积环境中,这些变化可能被古土壤记录下来。为了测试成土特征记录白垩纪-古近纪灭绝事件前后长期气候和短期气候变化的能力,研究人员对美国新墨西哥州西北部圣胡安盆地上白垩世(马斯垂克特)Naashoibito Ojo Alamo组成员和下古新世(达尼安)Nacimiento组的古土壤进行了研究,包括先前研究的数据。Naashoibito段细粒相由灰色至绿灰色和红带状泥岩组成,具有颜色斑驳、根迹、斑纹、带状组构、成土滑脱体和钙质结核等成土特征。除了地层底部的高色度层外,下Nacimiento组的古土壤与Naashoibito段的古土壤大致相似。相关剖面间成土特征的横向和纵向变异表明,土壤水文在空间和时间上从非常饱和到季节性良好排水,其时间变化受流域沉积速率控制。由于Naashoibito段顶部的不整合,没有精确记录白垩纪-古近纪边界的突变和/或灾难性气候事件。然而,在Nacimiento组的粘土矿物组合中,特别是在地层底部附近,而不是Naashoibito段,高岭石的存在表明,与马斯特里赫特晚期相比,大年纪早期的温暖和短暂(104年)间隔更强的风化条件。除了短暂的温暖间隔外,这两个地层沉积期间的整体古气候都是温暖的,并且一直是半湿润到湿润的,具有季节性,这表明圣胡安盆地在白垩纪-古近纪边界上没有发生实质性的长期(105 - 106)气候变化。