Mineralogy and Origin of Sediments From Drill Holes on the Continental Margin Off Florida, 1965-1969 (NODC Accession 7100714)

Drill cores obtained during the Joint Oceanographic Institutions' Deep Earth Sampling Program from the continental shelf, the Florida-Hatteras Slope, and the Blake Plateau off northern Florida are composed of sediments ranging in age from Paleocene to post-Miocene. Calcite is the dominant mineral in all the cores; dolomite is almost completely restricted to the shelf and slope cores. Aragonite persists in samples as old as Oligocene, but the magnesian calcite occurs only in post-Miocene samples. In general, only Miocene samples contain non-carbonate minerals in appreciable quantity. Phosphates are limited largely to the Miocene sediments. Here also, the clay minerals palygorskite, sepiolite, and montmorillonite are dominant. These clay minerals and the zeolites clinoptiolite and phillipsite in Miocene and older sediments suggest that volcanic activity was the principal source of non-carbonate deposition during much of the Tertiary. Heavy-mineral analyses suggest a southern Appalachian source for detrital materials. Terrigenous detrital material is scarce in most of the cores except for the surface samples on the continental shelf. The concentration of detrital quartz here probably resulted from reworking and winnowing by regression and transgression of the sea during Pleistocene rather than by increased influx of Terrigenous material.

Consolidated chertlike rocks consist of dominantly carbonate minerals in the near-shore holes and dominantly opaline cristobalite inthe Blake Plateau holes. Reflux dolomitization by dense brines produced in evaporative lagoons in the area of the continental shelf and later incursions of fresh ground water from the Florida peninsula may have lithified sediments in the near-shore holes. Only when conditions were favorable for silicification were sediments on the Blake Plateau appreciably consolidated.

联合海洋机构深部地球采样计划（Joint Oceanographic Institutions' Deep Earth Sampling Program）所获取的、采自佛罗里达北部外海大陆架（continental shelf）、佛罗里达-哈特拉斯斜坡（Florida-Hatteras Slope）以及布莱克高原（Blake Plateau）的钻探岩心，其赋存沉积物的年代范围为古新世（Paleocene）至中新世以后（post-Miocene）。所有岩心中的优势矿物均为方解石（Calcite）；白云石（dolomite）几乎仅分布于大陆架与斜坡岩心中。文石（aragonite）可在渐新世（Oligocene）及更老的样品中留存，但镁方解石（magnesian calcite）仅见于中新世以后的样品中。总体而言，仅中新世（Miocene）样品中含有数量可观的非碳酸盐矿物（non-carbonate minerals）。磷酸盐矿物（Phosphates）主要赋存于中新世沉积物中。该层位的黏土矿物同样以坡缕石（palygorskite）、海泡石（sepiolite）以及蒙脱石（montmorillonite）为主。中新世及更老沉积物中的此类黏土矿物与沸石类（zeolites）矿物——斜发沸石（clinoptiolite）和辉沸石（phillipsite）——表明，第三纪（Tertiary）多数时期的非碳酸盐沉积主要源自火山活动。重矿物分析（Heavy-mineral analyses）结果显示，碎屑物质（detrital materials）的物源为阿巴拉契亚南部（southern Appalachian）。除大陆架表层样品外，多数岩心中的陆源碎屑物质（Terrigenous detrital material）均较为匮乏。此处碎屑石英的富集，大概率是由更新世（Pleistocene）期间海退与海进（regression and transgression）作用造成的再沉积与淘蚀所致，而非陆源物质输入量增加引发。
近岸钻孔中的固结类燧石岩（Consolidated chertlike rocks）以碳酸盐矿物为主，而布莱克高原钻孔中的此类岩石则以玉髓质方英石（opaline cristobalite）为主。大陆架区域蒸发泻湖（evaporative lagoons）中形成的高密度卤水所引发的回流白云岩化作用，以及后续来自佛罗里达半岛（Florida peninsula）的新鲜地下水入侵，可能促使近岸钻孔中的沉积物发生固结成岩作用。仅当硅化作用（silicification）的条件适宜时，布莱克高原的沉积物才会发生明显固结。