Hummocky cross-stratification in the Kaling Formation, Kuala Lipis, Pahang

The Kaling Formation exposed at Kuala Lipis is composed of interbedded sandstone, mudstone and conglomerate. Fossil bivalves give a Mid-Late Triassic age. Hard shelled bivalves such as Myophoria and Costatoria suggest a high energy, shallow marine environment.

A recent visit to an exposure of the Kaling Formation in Kuala Lipis, Pahang, resulted in the discovery of hummocky cross-stratified sandstone (photo below).

 

The second photo also shows pebble lags at the base of a hummocky bed.

The presence of hummocky cross-stratification (HCS) lends further support to the interpretation of the Kaling Formation as shallow marine deposits.

Hummocky cross-stratification is formed by very large oscillating waves. Basically they are storm deposits. The availability of the storm deposits to rework the bottom sand and form HCS indicates a relatively shallow water depth, above storm wave base.

 

 

Waribole perlisensis

Trilobite fossils are relatively abundant in the mudstone of the basal Kubang Pasu Formation. However, articulated specimens are pretty hard to find.

The photo below is a specimen of Waribole perlisensis, a tiny trilobite species found in mudstone at Kampung Guar Jentik and Kampung Hutan Aji, Perlis. 

 

There are several species of tiny trilobites found in the basal Kubang Pasu Formation. Waribole is differentiated from the others by a strongly convex, ovate/bullet shaped glabella ( the ‘nose’- like feature on the head). 

The specimen shown here is almost complete, except for half of the head (top part of image). The specimen also shows that the glabella is pock-marked by small circle-shaped depressions.

Notice that the fossil is concave upward, and actually preserving the lower (inner) surface of the animals skeleton.

More commonly, Waribole is found as disarticulated parts in shelly accumulations in the mudstone. These may represent winnowed storm lag deposits.

 

Reference

Kobayashi, T. & Hamada, T. (1966). A new proetoid trilobite from Perlis, Malaysia (Malaya). Geology and Palaeontology of Southeast Asia 2: 245-250.

Tournquistia burtonae

Here’s another spiny brachiopod from the same red mudstone of the basal Kubang Pasu Formation. This one is pretty common and is already well known: Tournquistia burtonae

 

Spines grow out from the hinge of the shell (backwards), in this case, there are three pairs.

The spined chonetid brachiopods had several characteristics that made them well suited to live on the thick, soft mud substrate of the early Carboniferous shelf of NW Peninsular Malaysia. This includes flat to concavo-convex shells and long spines, which distributed the weight of the shell over a wide area and stabilised it on the seafloor (kind of like snow shoes). Their small size also avoided them from sinking.

There isn’t much written about the depositional environment of the basal Kubang Pasu Formation (except that they are shelf deposits). I’m still conducting a facies analysis of the basal red mudstone and hope to fill some of the details in the future. 

Hamada, T. (1969). Late Palaeozoic brachiopods from redbeds in the Malayan Peninsula, Geology and Paleontology of Southeast Asia 6: 251-264

Spiny Brachiopod

Another member of my fossil collection still unidentified: A tiny spiny brachiopod, again from the early Carboniferous, basal Kubang Pasu Formation of Perlis

Small, chonetid brachiopods are abundant from the red mudstones (Malayanoplia, Tournquistia), but none of these previously known species have spines that protrude to the front (the other species have spine protruding from the shell hinge), and none also have spines as long as these!!

A poorly preserved specimen was collected previously (Meor & Lee, 2004) and was tentatively identified as Chonetipustula. However, more specimens are needed.

Everytime I look at my brachiopod collection, I become rather frustrated, because I know I’m not good with brachiopods. The legendary Prof. Arthur Boucot, brachiopod expert, once had a look at my small collection, and made much more progress in a day than I had in months.

Anyway, back to classes

Refs

Meor Hakif Hassan and Lee, C.P., 2004. The depositional environment of the Mid-Palaeozoic redbeds at Hutan Aji, Perlis and its bearing on global eustatic sea level change. Bulletin of the Geological Society of Malaysia 48: 65-72

Tentaculitids from the Timah Tasoh Formation, Perlis

My paper on Early Devonian tentaculitids and graptolies from Perlis is now online

As a celebration, I’m going to post some nice photos of my specimens. Most of these are Nowakia (Turkestanella) acuaria acuaria and Nowakia (Turkestanella) acuaria posterior, associated with small styliolinids and also Metastyliolina. (Note: the scales are wrong due to technical problems with the microscope, sorry).

Nowakia (T) acuaria is present in great numbers in black shales of the Timah Tasoh Formation (or Upper Detrital Member) in Perlis and Langkawi. Other fossils associated with it are graptolites and small brachiopods, but these are relatively rare.

 

The high concentration of these fossils in marine black shales suggests that they were planktonic in nature, floating around in the ocean. Associated graptolites, which have also been interpreted as planktonic ocean floaters, supports this idea.

 

 

The rock is so rich with the fossils, that they actually make up the rock (Note to myself: a geochemical study in the future may be nice).

 

Fragment of graptolite rhabdosome. This one is still unidentified, but Monograptus langgunensis is relatively common in the rocks.

 

Reference:

 

Meor, H.A.H., Erdtmann, B.D., Wang, X. F. & Lee, C.P. 2012. Early Devonian graptolites and tentaculitids in northwest Peninsular Malaysia and a revision of the Devonian – Carboniferous stratigraphy of the region. Alcheringa: An Australasian Journal of Palaeontology, DOI: 10.1080/03115518.2012.702517.

Hummocky cross-stratification in the basal Chuping Limestone

Dear Reader,

Sorry for the long silence, but I’m taking advantage of the quiet time between semesters to do research and write some papers.

So, just a short post today on what we discovered in our recent fieldtrip to Perlis.

Hummocky cross-stratified grainstone at the base of the Permian Chuping Limestone

The undulating cross-laminations in the limestone beds indicate a shallow marine environment with strong waves due to storms.

A closer view

Maybe in the future, I’ll try to cover wave and storm deposition

Basic Tidal Sedimentology (Final Part)

This is the last of the posts on tidal sedimentology. Basically, these were done for my Marine Geology class at UM, but with a more sedimentological bent to them.

The periods by which tides oscillate are dependent upon the relative motions of the Earth, Moon and Sun. Several types of tidal periodicities are present due to the complex nature of the orbit of the moon around the Earth and of the Earth around the Sun. Some of these periodicities have been recognized in the rock record, based on quantitative
analyses of tidal bundles.

A commonly observed tidal periodicity is the semidiurnal period (two tides per day)

One oceanographic lunar day (one complete Earth rotation with respect to the moon) is 24.8412 hours long. As there are two tidal bulges on the earth, tides occur every 12.4206 hours.
Some coasts however, are affected by only one daily tidal cycle (diurnal period), due to basin configuration and shoreline complexities.

The neap-spring cycle works on longer time-scales

Spring tides occur when the moon and sun lie in a straight line relative to the Earth, resulting in greater than
average tidal ranges. Neap tides occur when the moon and sun are at right angles to each other relative to the Earth. The counteracting gravitational forces of the sun and moon result in smaller than average tidal ranges.

Alternating neap-spring cycles in areas affected by semidiurnal tides occur at a period of 14.77 days and contain 28 ebb-flood tidal cycles. For diurnal tides, the neap-spring cycle occurs at a period of 13.66 days and contains 14 ebb-flood tidal cycles.

Neap-spring cyclicity in well-preserved sequences of tide-generated cross-bed foresets is reflected in lateral thickness variations of the tidal bundles. A cyclic, sinusoidal pattern in bundle thickness is produced, composed of alternating packages of thick bundles deposited during higher energy spring tides, and thinner bundles deposited
during neap tides (Nio and Yang, 1991).

Bundle sequences in a cross-bed displaying neap-spring cyclicity

Each neap-spring cycle (14.7 days) in a semidiurnal setting will produce 28 to 29 bundles in the cross-bed.

Thick and thin tidal bundle packages (dark lines are mud drapes) interpreted as representing neap-spring cyclicity. Miocene Nyalau Formation, Sarawak.

Another example of cross-beds displaying neap-spring cyclicity (n=neap bundle packages; s=spring bundle packages). Again, from the Nyalau Formation around Bintulu, Sarawak.

Reference:

Nio, S.D., Yang, C.S., 1991. Diagnostic attributes of clastic tidal deposits. In: Smith, D.G.,
Reinson, G.E., Zaitlin, B.A., Rahmani, R.A. (Eds.), Clastic Tidal Sedimentology. Canadian
Society of Petroleum Geologists Memoir 16, 3-28.

Basic Tidal Sedimentology (Part III)

Herringbone cross-bedding is commonly interpreted as a product of tidal cyclicity. Herringbone cross-bedding is characterised by two vertically adjacent cross-beds with opposing foreset dip directions, interpreted as reflecting ebb-flood tidal current flow in a single ebb-flood tidal cycle

Herringbone cross-bedding, produced by a single ebb and flood cycle.

Herringbone cross-bedding, Miocene Miri Formation (in Miri, obviously)

True herringbone cross-bedding is probably rare, because many coastal environments display tidal asymmetry. Many pseudoherringbone cross-beds with vertically adjacent, opposing cross-beds most likely do not represent the deposits of a single ebb-flood cycle, but may actually represent separate tidal cycles with opposing dominant currents, or may just represent trough cross-bedding. True herringbone-cross-bedding is probably only present in settings displaying weak tidal asymmetry, and is probably restricted to small ripple and dune beds.

Pseudo-herring bone cross-bedding, Miocene Nyalau Formation, Bintulu. These are trough cross-beds formed by complex flow in a confined channel, rather than the product of single ebb-flood tidal cycles. However, these are still tidal deposits. It is just that individual tidal channels tend to show unidirectional flow (either in the flood or ebb direction).

Basic Tidal Sedimentology (Part II)

In settings with sufficient current velocity, ripples are formed during ebb and flood tidal flow, which are separated by mud drapes deposited during slackwater stages.

Depending on sediment supply, a continuum of rippled, tidal heterolithic deposits can be formed by repeated, periodic alternations of the ebb-flood cycle, including lenticular bedding, wavy bedding and flaser bedding (Reineck and Wunderlich, 1968).

Spectrum of heteroliths common in tide-dominated environments. Modified from Reineck and Wunderlich (1968).

Tidally deposited wavy and lenticular bedding, Miocene Lambir Formation, Sarawak

 

Lenticular bedding, Miocene Nyalau Formation, Sarawak

Reference

Reineck, H.E. Wunderlich, F., 1968. Classification and origin of flaser and lenticular bedding. Sedimentology 11, 99-104.

 

 

 

Basic Tidal Sedimentology (Part I)

Sediment transport and deposition in tide-dominated environments is characterised by periodic fluctuation of sea level (tides) with daily and monthly periodicities, and associated periodic reversals in tidal current direction.

The sedimentological consequences of these include regular interlayering of sand and mudlaminae of beds (rhythmites and tidal bundles), arrangement of these bundles forming a sinusoidal pattern of bundle thickness (neap-spring cyclicity), and evidence of tide reversals, including herringbone cross-bedding and bimodal palaeocurrent readings. 

Tides are the periodic fluctuations of water level in oceanic or lake bodies caused by the gravitational attraction exerted on the Earth by the Moon and Sun as they change positions relative to the earth. The moon, despite being smaller, has twice the effect on Earth tides compared to the sun, because it is closer to the earth. The Earth and Moon both revolve around each other, around a centre of mass located inside the Earth. The generation of tides can be explained by the interaction between gravitational
attraction and centrifugal force as the two bodies revolve around each other.

At the point on the Earth’s surface which is closest to the moon, the gravitational attraction of the moon is greater than the centrifugal force. On the opposite side of the Earth’s surface, farthest away from the Moon, the centrifugal force is greater than the gravitational attraction of the Moon. By applying a simple model, with the Earth surface completely covered by a single water body, the interaction between centrifugal force and gravitation produces two bulges of water, one facing the moon and one facing the opposite direction.

Rotation of the Earth results in the movement of these bulges around the Earth. Hence two high tides (under the bulges) and two low tides (halfway between bulges) form in a single daily rotation.

Tidal currents are important agents of transport and deposition in coastal environments, especially in estuaries and tidal channels. The daily rise and fall of tides generates periodically alternating landward-directed (flood) and seaward-directed (ebb) tidal currents.

In shallow coastal environments, a single tidal cycle is marked by a reversal in flow direction of tidal currents (ebb-flood tidal cycle). A single ebb-flood cycle is composed of a landward- directed current flow (flood tide) followed by a slackwater period, followed by a seaward-directed current flow (ebb tide) followed again by another slackwater period. The cycle is then repeated over and over.

If the tidal currents are strong enough to transport bedload, several types of bedform can be produced by
these tidal cycles. Rhythmic sand-mud interlayering is a common bedform generated in lower energy tidal settings.

Tidal rhythmites, Neogene deposits, Labuan Island

Sand layers are laid down during high energy ebb and flood tidal flow, while mud is deposited during lower energy slackwater periods in between tidal flows. Repeating ebb-flood tidal cycles eventually form a thick unit of sand-and mud interlayered at regular intervals.