Geochemistry at DSDP Leg 73 Holes@en

In the South Atlantic, at Sites 519 to 523, the dissolution of calcareous oozes ended in the formation of red clays rich in iron and manganese. The early authigenesis of manganese oxides and clays is described in Miocene marly calcareous oozes. The mineralogical and geochemical influences of basaltic basement weathering are shown by the occurrence of palagonite, authigenic clays, and oxides in the basal sediments. The development of red clay facies can be inhibited by local topographic and paleoceanographic changes, as at Site 520.在南大西洋519至523站位，钙质软泥的溶解作用最终形成了富铁锰红黏土。中新世泥灰质钙质软泥中记录了锰氧化物与黏土矿物的早期自生形成过程。玄武岩基底风化所产生的矿物学与地球化学效应，可通过基底沉积物中出现的橙玄玻璃（palagonite）、自生黏土矿物及氧化物得以体现。红黏土相的发育可被局部地形与古海洋学变化所抑制，如520站位所观测到的情况。