Markes E. Johnson

Williams College · Department of Geosciences

Organo-sedimentary deposits that result from fine-grained sediment trapping, binding, and likely precipitation (of carbonate) by microbes in flat-mat, branching, and dome-shaped constructions are termed microbialites. They were first identified as stromatolites by paleontologists well before the discovery of cyanobacteria that build the same kinds...

The boundary between land and sea is among the most extensive and extreme ecological barriers on planet Earth. Intertidal organisms living at this junction are subject to potentially lethal conditions related to desiccation, temperature fluctuations, and wave shock. Although difficult to quantify at a global level, rocky coasts account for between...

The last phase of the end-Ordovician extinction event involved substantial sea-level changes. The Oslo/Asker District in Norway is a rare place where the deeper-water early Hirnantian fauna is succeeded by the equivalent deeper-water Edgewood-Cathay Fauna. Both faunas are highly diverse, with the same small-shelled brachiopods, Onniella, Leangella,...

In order to understand the complex evolutionary processes and patterns that explain current island biodiversity, large datasets and long-term analysis are required. The Last Interglacial (LIG) was one of the warmest interglacials during the last million years. How species mobility changed during this period in the Macaronesia geographical region ha...

A population of large-shell brachiopods belonging to Stricklandia lens lens from the lower Silurian Solvik Formation is exposed in a capstone layer covering approximately 300 m2 on steeply dipping strata along the shores of Engervannet at Sandvika in southern Norway. Based on sample counts, a density estimated at 250 to 350 articulated shells per s...

This project follows a tradition of survey work undertaken to appraise physical and biological damage in the aftermath of hurricane-strength winds and waves at a given locality where conditions were well documented prior to the arrival of a particular storm. The locality is the 12 m limestone terrace at Arroyo Blanco on the eastern shores of Isla d...

O turismo subaquático em Santa Maria é uma das vertentes do turismo de Natureza sustentável com maior sucesso nesta ilha do Arquipélago dos Açores. Lugares como a “Baixa do Ambrósio” e as suas jamantas (entre outros grandes pelágicos), a “Pedrinha” e os peixes e grandes “leques” bivalves da espécie Pinna rudis (Linnaeus, 1758) que aí se avistam, ou...

Rhodoliths occur extensively around the shores of Fuerteventura Island in the Canary Archipelago, with Lithothamnion cf. corallioides being the most prominent species. A large number of rhodoliths end up washed onshore, the debris from which contributes to the formation of sediments constituting modern beaches. In a previous study by one of the co-...

ÁVILA S.P., R.S. RAMALHO, C.M. DA SILVA, M.E. JOHNSON, A. UCHMAN, B. BERNING, R. QUARTAU, P. MADEIRA, C.S. MELO, A.C. REBELO, L. BAPTISTA, S. ARRUDA, E. GONZÁLEZ, M.W. RASSER, A. HIPÓLITO, R. CORDEIRO, R. MEIRELES, V. RAPOSO, J. POMBO, R. CÂMARA, M.X. KIRBY, J. TITSCHACK, J.M. HABERMANN, R. VULLO, A. KROH, J.H. LIPPS, M. CACHÃO & J. MADEIRA, 2022....

It was with much interest that we read the comment made by Meco et al. (2022), regarding our work on "Range expansion of tropical shallow-water marine molluscs in the NE Atlantic during the last interglacial (MIS 5e): Causes, consequences and utility of ecostratigraphic indicators for the Macaronesian archipelagos". We welcome the discussion genera...

Controlled by ecological and physical factors, marine species distribution may vary due to global climatic changes that result from range expansion or contraction (the latter caused by local disappearances, i.e., extirpations). Spanning from 13° to 39°N, the Macaronesian region encompasses five archipelagos located within warm-temperate to tropical...

The Neogene is a globally recognized interval of geologic time that lasted from 23 until 1 [...]

Atmospheric carbon dioxide reached a record concentration of 419 parts per million in May 2021, 50% higher than preindustrial levels at 280 parts per million. The rise of CO2 as a heat-trapping gas is the principal barometer tracking global warming attributed to a global average increase of 1.2 °C over the last 250 years. Ongoing global warming is...

Located on the northern coast of Santa Maria Island (Azores Archipelago, central North Atlantic), the Lagoinhas section preserves a carbonate buildup correlated with Marine Isotope Substage (MIS) 5e, the warmest interval of the Last Interglacial. The buildup is formed mainly by crustose coralline algae (CCA) identified as Spongites sp., and some su...

This project examines the role of hurricane-strength events likely to have exceeded 119 km/h in wind speed that entered the Gulf of California from the open Pacific Ocean during Late Pleistocene and Holocene times to impact the granodiorite shoreline on Isla San Diego. Conglomerate dominated by large, ellipsoidal to subspherical boulders at the isl...

Pliocene body fossils from Santa Maria Island, Azores, have been studied for decades, but only more recently have ichnofossils received their due attention. Calcareous Pliocene deposits from the Baía de Nossa Senhora section contain numerous, diverse, well-preserved natural casts of invertebrate borings. The study of this type of fossils adds to kn...

This project examines the role of North Atlantic storms degrading a Late Pleistocene rocky shoreline formed by basaltic rocks overlying hyaloclastite rocks on a small volcanic peninsula connected to Gran Canaria Island in the central region of the Canary Archipelago. Conglomerate dominated by large, ellipsoidal to angular boulders eroded from an ad...

Unattached nodules of calcareous red algae (Rhodophyta), known as rhodoliths, are widely reported and studied in places that extend from the tropics to polar latitudes. Factors controlling the distribution of the rhodolith-forming species remain poorly understood. A review of the global distribution of present-day rhodolith beds was undertaken, col...

This project examines the role of tropical storms in the northeast Atlantic Ocean related to the post-mortem deposition of rhodoliths in coastal settings during Neogene to Holocene time with primary emphasis on Sal Island in the Cabo Verde Archipelago located 600 km off the coast of Senegal in northwest Africa. Fossil rhodoliths from 10 to 15 cm in...

Modern and palaeo-shores from Pleistocene Marine Isotope Substage 5e (MIS 5e) featuring prominent cobble/boulder deposits from three locations, on the southern and eastern coast of Santa Maria Island in the Azores Archipelago, are compared, in order to test the idea of higher storminess during the Last Interglacial. A total of 175 basalt clasts fro...

Sedimentary rocks are rarely preserved on reefless volcanic oceanic islands, because they are mostly exported from coastal areas towards the abyssal plains and such islands typically undergo subsidence. In contrast, the exceptional geological record of the uplifted Santa Maria Island (Azores) provides a unique opportunity to gain insight on such ro...

Fossil fishes are among the rarest in volcanic oceanic islands, their presence providing invaluable data for the understanding of more general (palaeo)biogeographical patterns and processes. Santa Maria Island (Azores Archipelago) is renowned for its palaeontological heritage, with representatives of several phyla, including the Chordata. Herein, w...

Site destruction and obfuscation are significant processes that hinder archaeological interpretations. This article focuses on a few natural taphonomic agencies impinging on archaeological site preservation in highland Central American settings. Precipitation and drainage are especially crucial in these riverine environments. Access to water for co...

The Azores, Madeira, Selvagens, Canary Islands and Cabo Verde are commonly united under the term “Macaronesia”. This study investigates the coherency and validity of Macaronesia as a biogeographic unit using six marine groups with very different dispersal abilities: coastal fishes, echinoderms, gastropod molluscs, brachyuran decapod crustaceans, po...

This work advances research on the role of hurricanes in degrading the rocky coastline within Mexico’s Gulf of California, most commonly formed by widespread igneous rocks. Under evaluation is a distinct coastal boulder bed (CBB) derived from banded rhyolite with boulders arrayed in a partial-ring configuration against one side of the headland on E...

Between Lagos and Albufeira, the Algarve coast of southern Portugal is marked by outcrops of the lower Miocene Lagos-Portimão Formation (LPF) consisting of yellow sandstone and coarse skeletal-rhodolithic limestone. This contribution focuses on the rhodoliths, their paleoecology, taphonomy, and biological composition, in the Lagos Biocalcarenite, t...

San Basilio basin in Baja California Sur (Mexico) exhibits distinct styles of volcanism that interrupted phases of normal sedimentation correlated with the Zanclean Stage (Lower Pliocene). Sea cliffs around a 4-km2 bay opening onto the Gulf of California are dominated by rhyolite, mudstone, sandstone, and limestone. Volcanism associated with re-sed...

A synthetic model is presented to enlarge the evolutionary framework of the General Dynamic Model (GDM) and of the Glacial Sensitive Model (GSM) of oceanic island biogeography from the terrestrial to the marine realm. The proposed “Sea-Level Sensitive” dynamic model (SLS) of marine island biogeography integrates historical and ecological biogeograp...

The increasing interest in geotourism has prompted the need for quantitative assessments of geosites as a fundamental step for the application of geoconservation strategies, in order to assure sustainable planning, management and use of natural resources. The improvement of methodologies used to evaluate geosites dictates the revision of previous a...

This study reports the first example of major erosion from hurricanes degrading a rocky coastline anywhere around the Gulf of California, although other sources of evidence are well known regarding the effect of inland erosion due to catastrophic rainfall in the Southern Cape Region of the Baja California peninsula and farther north. The uplifted,...

The bowl-shaped trace fossil Piscichnus waitemata Gregory 1991 appears in Pliocene sandstones from Santa Maria Island (Azores Archipelago), extensively excavated during a stage of island evolution when the volcanic edifice was a guyot (flat-topped seamount) isolated in the NE Atlantic. The host sediments were deposited at depths from the intertidal...

This is a preliminary interdisciplinary study on the enrichment of heterozoan carbonates on Dirk Hartog Island, Shark Bay, Western Australia, with particular reference to rhodolith (free-living non-geniculate) coralline algae. The current study aims to investigate the geological impact of shallow-water rhodoliths in Shark Bay, as well as fill criti...

Located 20 km south of Puertecitos on the Baja California Peninsula, Mexico, is a salt-crusted lagoon with a surface area of approximately 265,000 m2 that is isolated from the adjacent Upper Gulf of California by a 50-m wide berm. The berm rises 2 m above mean sea level extending for 530 m across the lagoon’s seaward front to bar replenishment by n...

A seabed sediment-sampling survey conducted on the Pico insular shelf found abundant rhodoliths between −64 and −73 m off the south coast of the island. These were small and mainly ellipsoidal in shape with a maximum diameter of 3.75 cm. Granules and small pebbles of eroded basalt were also a typical component of these samples. Thin algal crusts we...

Recent refinements in nomenclature with an emphasis on member-level organization of Hirnantian strata from Norway’s Oslo region provide a useful way to grasp depositional processes recorded in the last stage of the Ordovician system. Found in outcrops throughout the many small islands of the Oslofjord and the adjacent Bunnefjord, the multifaceted L...

Bioturbation structures from Ponta das Bicudas in Santiago Island, Cape Verde Archipelagoare located in coarse-grained biocalcirudite sandwiched between basaltic lavas of the Upper Pleistocene Assomada Formation. Four ichnospecies have been identified: Rhizocorallium commune irregulare, Rhizocorallium jenense versum, nov ichnosubsp., Alaichnus kabu...

The careers of Charles Darwin (1809–1882) and James Dwight Dana (1813–1895) are intimately linked to circumnavigations of the globe with the British mapping expedition on the H.M.S. Beagle (1831–1836) under Captain Robert FitzRoy and the United States Exploring Expedition (1838–1842) under Lieutenant Charles Wilkes. The former expedition mainly sur...

Past climate changes provide important clues for advancement of studies on current global change biology. We have tested large-scale biogeographic patterns through four marine groups from twelve Atlantic Ocean archipelagos and searched for patterns between species richness/endemism and littoral area, age, isolation, latitude and mean annual sea-sur...

Supplementary files from Marine Pollution Bulletin, 126: 101-112, Global change impacts on large-scale biogeographic patterns of marine organisms on Atlantic oceanic islands, by ÁVILA, S.P., R. CORDEIRO, P. MADEIRA, L. SILVA, A. MEDEIROS, A.C. REBELO, C. MELO, A.I. NETO, R. HAROUN, A. MONTEIRO, K. RIJSDIJK & M.E. JOHNSON (2018).

Diopatrichnus santamariensis isp. nov. from lower Pliocene sediments on Santa Maria Island in the Azores Archipelago (mid-North Atlantic) represents the third ichnospecies of Diopatrichnus Kern, as characterized by a vertical or inclined tube armored mainly with bivalve shells that are mostly perpendicular to the burrow axis and concave-up. The pol...

Distribution of living rhodoliths in the Macaronesian realm is limited by extensive rocky shores and narrow insular shelves that rapidly drop off beyond the 50-m isobath. Wind and wave erosion is most intense on north and northeast-facing shores due to the prevailing northeasterly trade winds over much of the region. Southern shores offer more shel...

During the Hirnantian Age (Late Ordovician) the Oslo Region was located in a subtropical setting with siliciclastic input and carbonate production. At that time the sea level fluctuated in the Oslo Region during three regressive-transgressive episodes, some of which involved subaerial exposure and coastal valley erosion. The last major sea-level dr...

Tectonic uplift on the shores of Bahía San Rafael in Mexico’s upper Gulf of California exposed a Pliocene delta system that covers a map area of 4 km². Subaerial dissection by arroyos entrenched during Pleistocene and post-Pleistocene time carved cross-sectional slices through the delta, showing its dominant construction resulting from massive tran...

Yongxing Island is a coral reef island formed by the growth and accumulation of corals and other skeletal fragments on a reef platform. The reef flat is developed around the entire island. The southeast reef flat and the north and northwest reef flat are asymmetrical in proportions, showing significant differences in reef‐flat width, patterns of se...

Coral-dwelling pyrgomatid barnacles (subfamily Ceratoconchinae) were widely dispersed throughout the Paratethys and Mediterranean seas as well as the Atlantic Ocean during the Neogene, but today are limited to the Western Atlantic. Herein, the paleobiogeographic origin and dispersal of the genus Ceratoconcha is studied based on a combination of fie...

Along the Canning Basin’s Lennard Shelf in Western Australia, the 80-km-long Oscar Range is composed of folded Palaeoproterozoic quartzite and phyllite and surrounded by limestones of the Great Devonian Barrier Reef including reef complex, related back-reef and lagoonal deposits of the Frasnian Pillara Limestone. The range represents an exhumed clu...

Rhodoliths are a common producer of carbonates on modern and ancient shelves worldwide, and there is growing evidence that they thrive on volcanic insular shelves. However, little is still known on how rhodoliths cope with the demands of this particularly dynamic environment. In this study, the focus is placed on fossil rhodoliths from a Pliocene s...

The trace fossil Macaronichnus segregatis is interpreted to be produced by opheliid polychaetes that feed on epigranular microbes and organic matter commonly abundant in shallow marine foreshore sands. Resulting traces are horizontal and typically random in orientation, but sometimes perpendicular to the shoreline. However, M. segregatis in Neogene...

The trace fossil Macaronichnus segregatis is interpreted to be produced by opheliid polychaetes that feed on epigranular microbes and organic matter commonly abundant in shallow-marine foreshore sands. Resulting traces are horizontal and typically random in orientation, but sometimes perpendicular to the shoreline. However, M. segregatis in Neogene...

The Tiombó conglomerate on Isla del Carmen in Baja California Sur represents a mega-delta deposited mainly during the middle Pliocene (early Piacenzian age). A cross-section with the characteristically arched profile of a fan delta is exposed in sea cliffs 60 m high that extend for 2 km along the east side of the fourth-largest island in Mexico’s G...

Maio is a volcanic island with an area of 269 km2 in the Cape Verde archipelago off the west coast of Africa. Although considered a leeward island, it absorbs NE trade winds that typically register 5 to 6 on the Beaufort Scale (moderate to fresh breeze). The trade winds produce ocean swells commonly 3.5 m in height that scour the island’s north coa...

Cook, A.G., Jell, P.A., Webb, G.E., Johnson, M.E. & Baarli, B.G., 21.4.2015. Septate gastropods from the Upper Devonian of the Canning Basin: implications for palaeoecology. Alcheringa 39, 519–524. ISSN 0311-5518 Septate murchisoniid gastropods are documented from the Upper Devonian (Frasnian) Pillara Limestone, Canning Basin, Western Australia. Tw...

Well preserved groove-borings related to the boring activity of regular sea urchins are preserved on Neogene rocks associated with rocky palaeoshores in a volcanic oceanic island (Santa Maria, Azores archipelago) and a continental margin (Foz da Fonte, CentralWest Portugal). The new trace fossil consists of a series of relatively deep grooves, with...

Massive fossil shell accumulations require particular conditions to be formed and may provide valuable insights into the sedimentary environments favouring such concentrations. Shallow-water shell beds appear to be particularly rare on reefless volcanic oceanic islands on account of narrow, steep and highly-energetic insular shelves where the poten...

Massive fossil shell accumulations require particular conditions to be formed and may provide valuable insights into the sedimentary environments favouring such concentrations. Shallow-water shell beds appear to be particularly rare on reefless volcanic oceanic islands on account of narrow, steep and highly-energetic insular shelves where the poten...

Well preserved groove-borings related to the boring activity of regular sea urchins are preserved on Neogene rocks associated with rocky palaeoshores in a volcanic oceanic island (Santa Maria, Azores archipelago) and a continental margin (Foz da Fonte, CentralWest Portugal). The new trace fossil consists of a series of relatively deep grooves, with...

The 1831–1836 voyage of H.M.S. Beagle under Captain Robert FitzRoy launched Charles Darwin's entry into the world of geology with two pioneering publications on oceanic islands to his credit. Best known is Darwin's 1842 contribution on the theory of atoll development from the subsidence of volcanic islands and coeval upward growth of coral reefs. T...

Crusts identified as a stromatolitic mat are described for the first time from a small, tectonically uplifted basin associated with a marine terrace along the central Gulf coast of the Baja California peninsula at Punta Chivato. Microscopic analyses of crustal laminae exhibit calcified features directly comparable to microbial processes that precip...

Many coasts feature sequences of Quaternary and Neogene shorelines that are shaped by a combination of sea-level oscillations and tectonics. We compiled a global synthesis of sea-level changes for the following highstands: MIS 1, MIS 3, MIS 5e and MIS 11. Also, we date the apparent onset of sequences of paleoshorelines either from published data or...

Baja California is one of the Earth’s last great wilderness areas that is easily accessible to travelers. Whether you enter from the United States to the north or from Cabo San Lucas to the south, it doesn’t take long to find yourself passing through a unique desert ecosystem of islands and land bound by the Pacific Ocean on the west and the Gulf o...

The Depauperate Zone from the base of the Ordovician (Katian) Maquoketa shale in Dubuque, Iowa, features a range of diminutive infaunal, epifaunal, nektonic and planktonic members with multiple growth stages. Fossils are preserved as phosphatized internal molds. In rare cases, shell replacement conserves growth lines. Sixteen species were recovered...

Carbonate factories on insular oceanic islands in active volcanic settings are poorly explored. This case study illuminates marginal limestone deposits on a steep volcanic flank and their recurring interruption by deposits linked to volcaniclastic processes. Historically known as Ilhéu da Cal (Lime Island), Ilhéu de Baixo was separated from Porto S...

The Oscar Range in Western Australia’s Canning Basin exhibits folded Proterozoic, quartzite, quartzite conglomerate, phyllite and metavolcanic rocks that survive with positive relief. Facies of the Pillara Limestone were deposited around this relief during Late Devonian (Frasnian) time. A segment of the Great Devonian Barrier Reef with a linear ree...

As a dense metamorphic rock with silica grains that are strongly fused, quartzite exposed on rocky shores is generally resistant to marine erosion. The longevity of quartzite coasts compared to those formed by other rock types is underscored by the preservation of many former islands that retain notable topographic relief as inliers of Archean and...

Rhodoliths are spherical growths (coralline red algae) that contribute bioclasts to coastal dunes in the Gulf of California (Mexico) and the Canary Islands (North Atlantic). Pleistocene dunes on Maio and São Nicolau islands in the Cape Verde archipelago were studied to quantify rhodolith contribution relative to other sources. Near Pilão Cão on Mai...

Two distinct Pleistocene assemblages from SE Santiago Island are comparable to modern analogues elsewhere in the Cape Verde Islands. A low-diversity Siderastrea radians assemblage lived atop basalt knobs surrounded by sand on a slope below a cliff. A Millepora alcicornis–Megabalanus azoricus assemblage occupied the cliff. The latter was a typical r...

Previous research on a small continental island called Bater Island in south-­central Inner Mongolia focused on palaeogeographic relationships in the context of the North China Block, and on the prevailing pattern of atmospheric and oceanic circulation interpreted from Ludlow (upper Silurian) strata surrounding an Ordovician diorite inlier. Prelimi...

Small basalt mounds with encrusting corals and inter-mound carbonate sandy zones with abundant rhodoliths corresponding to an ancient intertidal to shallow-water sea foor are exhumed from overlying volcaniclastic deposits and basalt lava fows at Pedra de Água on Ilhéu de Cima off Porto Santo, one of the islands of the northeastern Atlantic Madeira...