Basic studies on growth bands (daily, monthly and annual bands) of corals

虽然人们普遍认为，根据珊瑚的日和年生长增量，每年的天数会随着地质时间的推移而减少，但我们的研究表明，在每日和每月的地质年代学校准中，应该重新考虑古代珊瑚的生长带。用扫描电子显微镜（SEM）对日本更新世的两种硬核珊瑚化石进行了微小生长带计数，并测定了氧稳定同位素比值，得到了它们的年生长速率。实际上有两种不同类型的乐队，它们有不同的起源。在台湾龙骨中，每隔半个月形成一个条带。其波段宽度（0.05-0.20毫米）几乎与红珊瑚相当。在阔叶树（Tachyphyllia geoffroi）中，每条条带每天都会形成，条带宽度比前一种要细得多。这项研究表明，从红珊瑚中衍生出来的“每日”带以前并不被认为是每天形成的。此外，在古生代珊瑚中假设的月相周期可能真的是一年一次。

Although it has been widely accepted that the number of days per year have decreased through geological time based on daily and annual growth increments of corals, our study indicates that ancient coral growth bands should be reconsidered for daily and monthly geochronometric calibrations. Minute growth bands in two fossil scleractinian coral species from the Pleistocene of Japan were counted by SEM and the oxygen stable isotope ratio was measured to obtain their annual growth rates.There are really two different types of bands and they have different origins. In Truncatoflabellum formosum, each band is demonstrated to have formed per half-month interval.The band widths (0.05-0.20 mm) are nearly equivalent with those of rugose corals. In Tachyphyllia geoffroi, each band was formed daily and the band widths are much finer than the former species. This study suggests that "daily" bands derived from the rugose corals were not previously thought formed daily. Furthermore, lunar monthly periodicities postulated in the Paleozoic corals were probably really annual.