PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 CARBONATE DEPOSITIONAL ENVIRONMENTS Abdulkader M. Abed University of Jordan

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Depositional Environment are divided into: 1. Non – marine env. Lacustrine Calcrete=Caliche 2. Marine env. Carbonate platform Intertidal-supraidal Lagoonal

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Non-Marine environments 1. Lacustrine limestone Open lakes Closed lakes Carbonate deposition can be 1. Inorganic 2.Algal/microbial 3. skeletal sands

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Inorganic limestones Chemical precipitation due to carbonate saturation either by evaporation or due to loss of CO2 by photosynthesis or P/T changes. Lime mud precipitates. In agitated lakes ooids can form Aragonite, H Mg, L Mg calcite and dolomite, all can form depending on the Mg/Ca ratio.

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Algal/microbial limestones Lime mud forms by algae, cyanobacteria, microbes and phtoplankton blooms. Cyanobacteria forms stromatolites, e.g. Great Salt Lake, USA. Oncoids also, e.g. Lake Constance, Switzerland

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Skeletal sands These represent the fossis and fossil fragments livinf in lakes like Chara (green alagae), bivalves and gastropods.

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Lacustrine Facies Like marine facies: ooids and stromatolite (reefs) near shore in agitated water Lime mud further inside in the deeper parts of the lake. Sediments are usually laminated rhythmically, possibly seasonally, laminae consists of carbonates followed by organic matter laminae Closed lakes like the Dead Sea can deposit evaporites

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 2. Non-Marine Calcrete = caliche Precipitates by descending water in the soil B horizon Precipitation = mm/y & evaporation > precipitation can be dolomite = dolocrete Laminated & massive calcrete Peloids, pisoids, plant roots making veins fiiled with calcite Usually does not make continuous beds like marine deposites

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Marine carbonates and carbonate platforms Usually produces a thick sequence of marine carbonate of shallow water environment 5 types of platforms can be recognized

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11

Rimmed shelf = shallow water platform with distinct break of slope into deeper water. Reef and carbonate sand bodies usually develop along the high energy margin. Behind them, shelf lagoon develop with restricted water circulation. Near the shore: tidal flats and beach complex develop.

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Reef Carbonate sand Shelf lagoon Tidal flats & beaches Rimmed shelf

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11

Carbonate Ramp Is a gently sloping surface with a generally high energy shorelines and a quiet deeper environment

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11

Intertidal-Supratidal carbonates Intertidal or tidal flats lies between high and low tide while supratidal is above high tides. Tidal flats : Lime mud but some times carbonate sand Supratidal can have evaporites like gypsum and anhydrite, and dolomite

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Supratidal Intertidal Tidal flat Subtidal Lime mudstone Rare grainstones Restricted fossils Fenestrate porosity Microbial mats Stromatolites Bioturbation Herringbone cross bedding Mud cracks Lime mudstone Dolomite Evaporites Fossil diversity Carbonate Sand Below FWWB lime mud

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Carbonate sand

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Carbonate sands

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Lagoonal Carbonates Lagoons are subtidal areas behind barriers, with restricted water bodies, different from normal open marine water. Lime mudtsone low fossil diversity Pellets Abundant bioturbation No grainstone

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Conditions of Carbonate Deposition

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Beaches and Barrier Islands When sea level rises it sometimes floods the land faster than the beach can move inland, resulting in ponded water (the lagoon) behind the beach (now barrier island). As a result there are two beaches, one on the ocean side and one on the lagoon side. Barrier Island Storm washover deposits Landward beach Oceanside beach Transition Environments Lagoon

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 REEFS A carbonate build up that posses a wave resistant framework constructed by organisms. Other related terms are: Patch reef: small & circular in shape Fringing reef: attached to the coast with no lagoon Atoll: within the ocean and enclosing a lagoon Bioherm: As reef Buildup: a general term for accumulated organisms such as reef …etc

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 REEFS 1.Warm Water Carbonates form only in tropical waters between 30 degrees north and south. The formation of highly consolidated reefs only occur where the temperature does not fall below 18°C for extended periods of time Shallow Water The luxurient abundance of life requires photosynthesis. If the water is too deep light is filtered out. 2. Clear Water Usually means an absence of “turbidity”, that is clastic particles Clastic particles block out sunlight needed for photosynthetic productivity, and clog the filter feeding apparatus of organisms. Inorganic carbonate precipitation requires supersaturation of the water with carbonate favored by high temperatures. 4. Agitated Water Thus usually means wave and tidal action. Part of this is to bring in the abundant nutrients to support biological activity, and part to form specific particles such as oolites.

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 The exceptionally clear water as seen in this reef is a requirement for carbonate formation.

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Reef-building organisms Recent reefs: corals + coraline algae less important are sponges, serpulites, oysters and certain gastropods. In the geological many other groups of organisms were involved in reef buildups

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 The reef system can be divided into three parts: 1. Fore reef (reef front, into the deeper environment) 2. The reef itself (the reef crest and flat) 3. Back reef: lagoon behind the reef. Reefs are a good reservoir for oil and gas.

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Pelagic limestones Deeper water environment in the open ocean > 100 m. Source of carbonates are planktonic organism; e.g. foraminifera, coccoliths, … Very little siliclastic clays Sediments are called calcareous ooze and after lithification become chalk

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11 Because the source of the sediment s is from sea surface, then after a certain depth called the carbonate compensation depth (CCD). In tropical water Calcite CCD: m Aragonite CCD: <2000m In tempertae and cooler water it is much less.

PROF. ABDULKADER M. ABED UNIVERSITY OF JORDAN 20/11