There, fifty-seven samples were dated using the uranium‑thorium (U/Th) method. Field observations and coral sampling were carried out on conglomerates from three atolls located in the north-western Tuamotu, namely, Takapoto, Takaroa and Fakarava. These are regarded as mainly generated by storm activity during the mid-late Holocene. In French Polynesia, low-lying, reef islands, composed of unconsolidated skeletal material rest on cemented conglomerate platforms. Although its significance in terms of still-sea level was recently questioned by Stoddart and Murphy (2018), the physical limit between the two diagenetic subsequences was assumed to delineate the position of a former water marine table. As emphasized by McLean (2011aMcLean (, 2011b, lithification has been probably favored by stabilization of deposits and retention of saturated waters by interstitial fine-sized skeletal matrices infilling voids between coarser clasts. The determination of lithification patterns of reef conglomerate in a number of French Polynesian Islands Pirazzoli et al., 1985) revealed that lithification took place through an early marine diagenetic sequence, vertically subdivided into two distinct subsequences: an upper, marine vadose subsequence, defined from the occurrence of grain-contact to asymmetric, gravitational cements, and a lower, phreatic subsequence, defined from isopachous fibrous to prismatic cements and/or homogeneous micrite cements partly to completely infilling intergranular voids.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |